GB2590111A

GB2590111A - Straight through fluid trap

Info

Publication number: GB2590111A
Application number: GB2013854.1A
Authority: GB
Inventors: Simmen Jonathan; Ernest Howe Derek; Bristow Adrian
Original assignee: Polypipe Ltd
Current assignee: Polypipe Ltd
Priority date: 2019-09-06
Filing date: 2020-09-03
Publication date: 2021-06-23
Anticipated expiration: 2040-09-03
Also published as: GB2599515A; GB2599515B; GB202013854D0; GB2599516B; GB2590111B; GB202116430D0; GB202116432D0; GB2599516A; GB201912878D0

Abstract

A straight through fluid trap 10 comprising: an interior 22 defined by a housing , aligned A inlet 12 and outlets 14 with a flow path 24 between the two, a passageway or hole through the housing to an outer surface with an air admittance valve 30 in the interior which creates a fluid path between the flow path and the passageway when open and where the valve isolates the passageway when it is closed. The valve may be positioned so that fluid is diverted around it. The flow path may have a first portion where the fluid is directed downwards and a second portion which directs the fluid upwards. The air admittance valve may be open when the flow path is at negative pressure and may be closed when the flow path is at non-negative pressure. The flow path may have a diverter 48 which has a ridge through the centre of the housing and two concave surfaces and the flow path may have a dip tube 54 extending from the outlet end. A fluid trap comprising a dip tube, and a flow path divider are also claimed.

Description

Straight Through Fluid Trap

FIELD

The present invention relates to a straight through fluid trap comprising an air admittance valve, more particularly, but not exclusively, a straight through fluid trap comprising an air admittance valve for use in a plumbing system.

BACKGROUND

Fluid traps are used in plumbing systems or other fluid flow systems (e.g. oil refineries) to prevent foul smelling or dangerous gases/fumes from escaping through pipework. Typically, this is achieved via use of a flow path which is shaped so that fluid is retained within the trap, creating a fluid seal which prevents gases passing through the trap.

Common types of fluid traps include U-bend fluid traps, wherein a fluid seal is formed in the U-shaped portion of the trap. In addition, any debris passing through the system may accumulate in the U-shaped portion, rather than passing through the trap. This prevents pipework blockages in parts of the system downstream of the fluid trap.

The problem with U-bend type fluid traps is that the U-shaped pipe portion is often quite large, and the arrangement of the inlets and outlets means that they may not be suitable for use in compact environments (e.g. in straight-through pipework running under a small sink).

Another type of fluid trap is a straight through fluid trap, which typically includes an S-shaped portion. This type of fluid trap may be more suitable than U-bend type traps for connecting with existing straight pipework, but may still be unsuitable for compact environments due to the large size of the S-shaped portion.

If a negative pressure forms in a fluid system downstream of a fluid trap, this may cause fluid retained in the fluid trap to be syphoned. This may reduce or prevent the ability of the fluid seal to function as required. In addition, syphoning of the fluid seal may cause undesirable gurgling noises. These problems have been overcome by installing an air admittance valve in a fluid system downstream of the fluid trap.

An air admittance valve defines a passageway between the interior of the fluid system and the environment in which it is disposed, which is sealable via a valve member. Under non-negative system pressures the passageway is sealed (i.e. no air or fluid can enter or exit the system). In response to a negative pressure in the fluid system, the valve member of an air admittance valve is moved such that air is permitted to flow into the fluid system to equalise the pressure. This prevents syphoning of the fluid retained in the fluid trap, and preserves the fluid seal.

Adding an additional air admittance valve to a fluid system requires additional connections/pipework. This results in a fluid system which is less compact, as well as more expensive and time-consuming to install and maintain, than a system with no air admittance valve.

The present invention seeks to overcome or at least mitigate one or more problems associated with the prior art.

SUMMARY

According to a first aspect of the invention, a straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet is provided. The straight through fluid trap comprises: a housing defining an interior region; a flow path through the interior region for communication of fluid between the inlet and the outlet; a passageway through the housing from an outer surface of the housing to the interior region; and an air admittance valve located in the interior region; wherein the straight through fluid trap is configured to switch the air admittance valve between an open state, in which the flow path is in fluid communication with said passageway, and a closed state, in which the flow path is isolated from said passageway.

Advantageously, such a fluid trap includes an internal air admittance valve. This means that when using the fluid trap in a fluid system, there is no need to connect an additional air admittance valve to the system. Therefore, this provides a more compact arrangement. Furthermore, a straight-through fluid trap (i.e. an axial centre of the inlet is parallel to an axial centre of the outlet) may offer a more compact arrangement than alternative trap types such as U-bend type traps.

In exemplary embodiments, the air admittance valve is located entirely within the interior region defined by the housing, such that the air admittance valve is surrounded by the housing.

Having the air admittance valve located entirely within the interior region defined by the housing, such that the air admittance valve is surrounded by the housing, provides a compact arrangement and reduces the likelihood that the air admittance valve could become damaged in use (e.g. as opposed to an arrangement in which an MV is fitted external to the housing and which thus projects from the housing in such a way that it could be impacted and damaged).

In exemplary embodiments, the air admittance valve is located within the interior region such that fluid is diverted around the air admittance valve as it travels along the flow path, in use.

In this way, the air admittance valve is located within the interior region which the fluid flows through (i.e. it is integral to the fluid trap, rather than an additional component).

In exemplary embodiments, the housing defines a bore, wherein the air admittance valve is arranged within said bore.

Advantageously, locating the air admittance valve within the bore of the housing provides a more compact arrangement than having a 'bolt-on' type air admittance valve.

In exemplary embodiments, the flow path comprises a first portion intended to direct fluid downwards in use and a second portion intended to direct fluid upwards in use, wherein the first and second portions of the flow path are located within said bore, and wherein the air admittance valve is in fluid communication with the first and/or second portions of the flow path.

In other words, the key components of the fluid trap are all located within the bore of the housing which defines the internal region. This provides a neat and compact arrangement.

In exemplary embodiments, an axial centre of the air admittance valve and an axial centre of the inlet and/or an axial centre of the outlet and are arranged coaxially.

In other words, air admittance valve is directly inline with the inlet and/or outlet. Advantageously, this provides a more compact arrangement than a fluid trap with an air admittance valve unit "bolted on" to the side of the trap.

In exemplary embodiments, the straight through fluid trap is configured so that the air admittance valve is in the open state when the flow path is at a negative pressure, in use.

In this way, when the flow path experiences a negative pressure, the air admittance valve opens which allows air to enter the flow path, to equalise the pressure in the system.

In exemplary embodiments, the straight through fluid trap is configured so that the air admittance valve is in the closed state when the flow path is at a non-negative pressure, in use.

In this way, the air admittance valve does not permit a back flow of air or fluid from the flow path out of the passageway. This prevents foul smells from the downstream portion of the flow path being transmitted to the environment surrounding the fluid trap. For example, in the case where the fluid trap is used in a domestic plumbing system, this functionality prevents foul smells from the drain system from being communicated to the area surrounding the bath, toilet, sink or other plumbing facility.

In exemplary embodiments, the air admittance valve comprises a valve seat and a valve member having a seal surface configured for engagement with the valve seat when the air admittance valve is in the closed state.

In exemplary embodiments, the valve member comprises a rear surface on an opposing side of the valve member to the seal surface, wherein the rear surface is in fluid communication with the flow path, such that a positive or negative pressure in the flow path is communicated to the rear surface to control the state of the air admittance valve.

In this way, a negative pressure acting on the rear surface causes the seal surface to separate from the valve seat. This provides a fluid communication with the passageway through the housing, which allows air to enter the flow path to equalise the pressure.

In exemplary embodiments, the valve member is received in one or more receiving formations in the interior region.

In exemplary embodiments, a first receiving formation of the one or more receiving formations is configured to receive a first stem of the valve member.

In exemplary embodiments, the first receiving formation and first stem are configured for interlocking engagement to secure the first stem in the first receiving formation.

In exemplary embodiments, the air admittance valve is an umbrella valve.

An umbrella valve has been found to be particularly suitable for providing reliable performance of the air admittance valve.

In exemplary embodiments, the valve member comprises a stem and a resilient disc connected thereto, wherein the resilient disc defines the seal surface, and wherein the air admittance valve is configured so that the seal surface is biased towards the valve seat when the valve member is fitted to the trap in use.

In exemplary embodiments, the resilient disc also defines the rear surface, wherein a first pressure is communicated to the rear surface and a second pressure is communicated to the seal surface in use, and wherein the air admittance valve is configured to resiliently deform away from the valve seat when a pressure differential between the second pressure and the first pressure is greater than a biasing force acting on the resilient disc.

In exemplary embodiments, the air admittance valve is a poppet valve and the valve member is a poppet, wherein the poppet is located between first and second poppet receiving formations in the interior region, wherein the first poppet receiving formation is arranged to align the poppet on a first side of the seal surface and the second poppet receiving formation is arranged to align the poppet on a second side of the seal surface.

In this way, the poppet is located at both ends, which prevents misalignment. This increases the reliability and longevity of the valve seal in the closed position.

In exemplary embodiments, the poppet further comprises a substantially cross-shaped, H-shaped or T-shaped cross-section, wherein the first poppet receiving formation is a first boss in the interior region and a the second poppet receiving formation is a second boss in the interior region.

In exemplary embodiments, the poppet comprises a first stem extending orthogonally from said seal surface and a second stem extending orthogonally from said rear surface, and wherein the first stem of the poppet is located in the first boss in the interior region, and the second stem of the poppet is located in the second boss in the interior region.

In exemplary embodiments, the flow path comprises a flow diverter proximal the inlet of the trap, said flow diverter being arranged to divert fluid flow towards the outer surface of the housing, in use; preferably, wherein the flow diverter comprises a body haying a ridge extending through an axial centre of the housing from a first side of the housing to an opposing side of the housing, wherein the body further comprises two concave surfaces located on opposing sides of said ridge so that, in use, fluid flow is directed away from the axial centre of the housing towards an outer surface of the housing.

Advantageously, this directs flow around the air admittance valve located in the axial centre of the interior region.

In exemplary embodiments, the linear ridge comprises a first end and a second end, wherein the width of the linear ridge thickens towards said first and second ends in plan view (e.g. the ridge has a biconcave or "apple core" shape in plan view).

Such a flow diverter shape has been found to optimise the fluid flow rate through the trap.

In exemplary embodiments, the flow path comprises a first fluid diversion formation and a second fluid diversion formation, said first and second fluid diversion formations being configured to change the direction of a fluid flow therethrough in use (e.g. two 180 degree turns), wherein the first fluid diversion formation is closer to the outlet than the second fluid diversion formation, so that a fluid seal is provided between the fluid diversion formations in use.

Advantageously, having fluid diversion formations which provide a fluid seal in use prevents foul smells from passing from the outlet to the inlet. For example, in a domestic plumbing situation, this prevents foul smells from the drain passing to the plug hole of a sink, bath or other plumbing facility.

Furthermore, since the straight through fluid trap includes an air admittance valve, this fluid seal is prevented from being syphoned in the event that a negative pressure is experienced downstream of the fluid diversion formations. The air admittance valve also offers noise reducing benefits, by preventing syphoning and the gurgling noises associated with this.

In addition, this arrangement ensures that debris entering the trap via the inlet does not pass through to the outlet, since it accumulates between the fluid diversion formations. In this way, the trap may be emptied and cleaned easily, preventing blockages forming downstream of the trap (which may be more difficult to access to clean/remove).

In exemplary embodiments, the flow path comprises a dip tube extending in a direction from the outlet of the trap towards the inlet of the trap, and wherein the dip tube extends from a base end proximal the outlet of the trap towards a tip end distal the outlet of the trap.

In this way, a first of the fluid diversion formations is provided by the base end of the dip tube and a second of the fluid diversion formations is provided at the tip end of the dip tube. Advantageously, this arrangement ensures that a fluid seal is formed between the dip tube and the housing, in use. This fluid seal will be of a height equal to the length of the dip tube. This fluid seal prevents foul smells from passing from the outlet to the inlet. For example, in a domestic plumbing situation, this prevents foul smells from the drain passing to the plug hole of a sink, bath or other plumbing facility.

In exemplary embodiments, an axial centre of the dip tube is arranged coaxially with the axial centre of the inlet and/or outlet and/or air admittance valve.

Advantageously, this arrangement is compatible with a substantially tubular straight-through housing, which provides neatness and compactness.

In exemplary embodiments, the flow path further comprises one or more conduits each extending from a first conduit end proximal the flow diverter, to a second conduit end proximal the base end of the dip tube.

In this way, fluid is directed to the base of the dip tube, which ensures it must undergo two direction changes (i.e. one at the base and one at the tip of the dip tube) rather than passing directly through the tip of the dip tube and out the outlet.

In exemplary embodiments, each of the one or more conduits is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by one or more side walls extending from the first conduit end to the second conduit end, such that the conduit defines a substantially tubular passageway.

By having a conduit which is enclosed by side walls on each of the first, second, third and fourth sides, fluid may only enter or exit the conduit at the first and second conduit ends, which ensures fluid is directed correctly around the flow diversion features of the trap. In other words, there is no short-cut flow path from the conduit to the tip end of the dip tube, which ensures that a fluid seal is created around the dip tube in use.

In exemplary embodiments, the flow path further comprises one or more channels defined between the first and second sides of the one or more conduits, wherein each of the one or more channels provides a fluid communication between the second conduit end and the tip end of the dip tube.

Advantageously, such channel(s) complete the flow path by providing a portion of the flow path which is needed for fluid to pass from the second conduit end at the base of the dip tube to the tip end of the dip tube (before passing to the outlet through the dip tube).

In addition, this arrangement ensures that debris entering the trap via the inlet does not pass through to the outlet, since it accumulates at the bottom of the interior region (around the base of the dip tube), rather than passing upwards through the one or more channels defined by the first and second sides of the one or more conduits. In this way, the trap may be emptied and cleaned easily, preventing blockages forming downstream of the trap (which may be more difficult to access to clean/remove).

In exemplary embodiments, the distance between the second conduit end and the tip end of the dip tube is in the range of 30mm to 120mm; preferably, in the range of 50mm to 100mm; more preferably, in the range of 70mm to 80mm.

Advantageously, this distance provides a fluid seal of suitable depth to provide the advantage of preventing foul smells from passing from the inlet to the outlet.

In exemplary embodiments, the housing comprises: an upper part defining said inlet and having a first engagement formation; and a lower part defining said outlet and having a second engagement formation; wherein the upper and lower parts are connectable via engagement of the first and second engagement formations (e.g. complementary threads).

In this way, the housing may be easily opened to allow access to the components located in the interior region. This allows cleaning, replacement of seals or fixing of broken components to be easily carried out.

In exemplary embodiments, an interior region of the upper part comprises a flow diverter arranged to divert fluid flow towards the outer surface of the housing.

In exemplary embodiments, an interior region of the lower part comprises a dip tube extending from a base end proximal the outlet of the lower part towards a tip end distal the outlet of the lower part.

In exemplary embodiments, the flow path further comprises an internal body located within the interior region, wherein the internal body comprises one or more conduits each extending from a first conduit end proximal the flow diverter to a second conduit end proximal the base end of the dip tube, and a hollow central region therebetween; preferably, wherein the dip tube is located within the hollow central region of the internal body.

In this way, the conduit(s) of the internal body is (are) configured to fit around the dip tube. This provides a compact arrangement which minimises the size of the fluid trap.

In exemplary embodiments, the or each conduit is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by one or more side walls extending from the first conduit end to the second conduit end, such that the conduit defines a substantially tubular passageway.

In exemplary embodiments, the internal body comprises a slot located on the or a side wall of the one or more conduits, between the first and second conduit ends.

In this way, any fluid or debris that does not enter the conduit(s) at the first conduit end(s) does not collect between the conduit(s) and the housing. Rather, it passes through the slot(s) and into the conduit(s).

In exemplary embodiments, the air admittance valve comprises a valve seat and a valve member having a seal surface configured for engagement with the valve seat, wherein the first end of the internal body and the interior formation of the upper part define an air admittance valve chamber therebetween.

In this way, the valve member of the air admittance valve is located between the internal body and the upper part. This allows the valve member to be easily accessed (e.g. for cleaning or replacement) by removing one or both of the upper part and internal body.

In exemplary embodiments, the air admittance valve chamber comprises a first chamber side in fluid communication with the hollow central region and a second chamber side in fluid communication with the passageway, and wherein the first chamber side is sealed from the second chamber side via the seal surface of the valve member when the air admittance valve is in the closed state, in use.

In exemplary embodiments, the first end of the internal body comprises at least one aperture defining the fluid communication between the first chamber side and the flow path.

In this way, the air admittance valve is configured to introduce air to the hollow central region of the internal body (which houses the dip tube) when a negative pressure forms in said hollow central region (e.g. via negative pressure being formed in the system, downstream of the dip tube). This equalises the pressure, and prevents the water seal surrounding the dip tube from being syphoned down the dip tube, which could reduce the ability of the water seal to prevent foul smells from reaching the inlet of the fluid trap.

In exemplary embodiments, the air admittance valve comprises a valve seat and a poppet having a seal surface configured for engagement with the valve seat, wherein the poppet comprises a substantially cross-shaped cross-section, wherein the internal body comprises a first end located distal the outlet of the lower part, and wherein the first end of the internal body comprises a first boss for locating the poppet; preferably, wherein the upper part comprises an interior formation comprising a second boss for locating the poppet.

In this way, the poppet of the air admittance valve may be received between the internal body and the upper part. This allows the poppet to be easily accessed (e.g. for cleaning or replacement) by removing one or both of the upper part and internal body.

In exemplary embodiments, a first end of the internal body and an interior formation of the upper part define an air admittance valve chamber therebetween, wherein the air admittance valve chamber comprises a first chamber side in fluid communication with the hollow central region and a second chamber side in fluid communication with the passageway, and wherein the first chamber side is sealed from the second chamber side via the seal surface of the poppet when the air admittance valve is in the closed state, in use.

According to a second aspect of the invention, a straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet is provided. The straight through fluid trap comprises: a housing defining an interior region; and a flow path through the interior region for communication of fluid between the inlet and the outlet; wherein the flow path comprises a dip tube extending in a direction from the outlet of the trap towards the inlet of the trap, and wherein the dip tube extends from a base end proximal the outlet of the trap towards a tip end distal the outlet of the trap; wherein the flow path further comprises one or more conduits each extending from a first conduit end proximal the inlet of the trap, to a second conduit end proximal the base end of the dip tube; and wherein the flow path further comprises one or more channels defined by the sides of the one or more conduits, wherein each of the one or more channels provides a fluid communication between the second conduit end and the tip end of the dip tube.

In exemplary embodiments, the or each conduit is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by one or more side walls extending from the first conduit end to the second conduit end, such that the conduit defines a substantially tubular passageway, wherein, the at least one channel is defined by the side walls of the at least one conduit.

In exemplary embodiments, the one or more channels are defined between the first and second sides of the one or more conduits.

Advantageously, the combination of the conduit(s), channel(s) and dip tube ensures that fluid flowing along the flow path must undergo two direction changes (i.e. one at the base and one at the tip of the dip tube) rather than passing directly to the tip of the dip tube and out the outlet. This results in a fluid seal being formed between the dip tube and the housing, in use.

The fluid seal will be of a height equal to the length of the dip tube. This fluid seal prevents foul smells from passing from the outlet to the inlet. For example, in a domestic plumbing situation, this prevents foul smells from the drain passing to the plug hole of a sink, bath or other plumbing facility.

In addition, this arrangement ensures that debris entering the trap via the inlet does not pass through to the outlet, since it accumulates at the bottom of the interior region (around the base of the dip tube), rather than passing upwards through the at least one channel defined by the side walls of the at least one conduit. In this way, the trap may be emptied and cleaned easily, preventing blockages forming downstream of the trap (which may be more difficult to access to clean/remove).

In exemplary embodiments, the flow path further comprises a flow diverter proximal the inlet of the trap, said flow diverter being arranged to divert fluid flow towards the first conduit end, in use.

In exemplary embodiments, an axial centre of the dip tube is arranged coaxially with the axial centre of the inlet and/or outlet.

According to a third aspect of the invention, a straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet is provided. The straight through fluid trap comprises: a housing defining an interior region; and a flow path through the interior region for communication of fluid between the inlet and the outlet; wherein the housing comprises: an upper part defining said inlet and having a first engagement formation; and a lower part defining said outlet and having a second engagement formation; wherein the upper and lower parts are connectable via engagement of the first and second engagement formations (e.g. complementary threads).

Advantageously, this arrangement allows the housing to be easily opened to allow access to the components located in the interior region. This allows cleaning, replacement of seals or fixing of broken components to be easily carried out.

In exemplary embodiments according to the first, second or third aspects of the invention, the inlet or outlet comprises a telescopic arrangement.

In this way, the length of the fluid trap may be easily altered. Advantageously, this provides an easier method of installing the fluid trap (e.g. as a replacement in existing pipework, without having to alter the rest of the pipework).

In exemplary embodiments according to the first, second or third aspects of the invention, the straight through trap comprises one or more seals (e.g. 0-ring seals) arranged such that the trap is configured to withstand back-pressure without leaking, in use.

In this way, if a blockage downstream of the trap causes the trap to fill entirely with fluid and debris, the fluid would not leak out of the trap body.

According to a fourth aspect of the invention, a flow diverter for use within a fluid trap is provided. The flow diverter comprises a body having a linear ridge defining a transverse axis and two concave surfaces located on opposing sides of said ridge so that, in use, fluid flowing towards the flow diverter in a direction perpendicular to the transverse axis is directed along the concave surfaces and away from the transverse axis.

Such a flow diverter shape has been found to optimise the fluid flow rate around the flow diverter. This may improve throughput through a fluid trap including the flow diverter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are now described by way of example only with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a straight through fluid trap according to an embodiment; Figure 2 is cross-sectional view of the straight through fluid trap of Figure 1; Figure 3 is a cross-sectional view of the straight through fluid trap of Figures 1 and 2, rotated 90 degrees about the longitudinal axis of the fluid trap with respect to Figure 2; Figure 4 is a cutaway view of the air admittance valve section of the straight through fluid trap of Figures 1 to 3; Figure 5 is an exploded view of the modular housing, valve member and internal body of the straight through fluid trap of Figures 1 to 3; Figure 6 is an isometric view of the internal body of the straight through fluid trap of Figures 1 to 3 and 5; Figure 7 is an isometric view of the underside of the internal body of Figure 6; Figure 8 is a cross-sectional view of a straight through trap according to a further embodiment; Figure 9 is cross-sectional view of a straight through fluid trap according to a further embodiment; Figure 10 is a cross-sectional view of the straight through fluid trap of Figures 9, rotated 90 degrees about the longitudinal axis of the fluid trap with respect to Figure 9; Figure 11 is a cutaway view of the air admittance valve section of the straight through fluid trap of Figures 9 and 10; Figure 12 is an exploded view of the modular housing, valve member and internal body of the straight through fluid trap of Figures 9 and 10; Figure 13 is an isometric view of the internal body of the straight through fluid trap of Figures 9, 10 and 12; Figure 14 is an isometric view of the underside of the internal body of Figure 13; Figures 15 and 16 are isometric views of a flow diverter for use in a fluid trap, according to a further embodiment.

DETAILED DESCRIPTION

Referring to Figures 1 to 3, a straight through fluid trap is indicated generally at 10. The straight through fluid trap 10 has a housing 20. The housing 20 includes an inlet 12 and an outlet 14. The housing defines an interior region 22. An axial centre of the inlet 16 is parallel to an axial centre of the outlet 18. A flow path 24 is provided through the interior region 22 for communication of fluid between the inlet 12 and the outlet 14. A passageway 26 is provided through the housing 20 from an outer surface 28 of the housing 20 to the interior region 22.

The straight through fluid trap 10 further includes an air admittance valve 30 located in the interior region 22. The straight through fluid trap 10 is configured to switch the air admittance valve 30 between an open state, in which the flow path 24 is in fluid communication with the passageway 26, and a closed state, in which the flow path 24 is isolated from the passageway 26.

The air admittance valve 30 is located entirely within the interior region 22 defined by the housing 20, such that the air admittance valve 30 is surrounded by the housing 20.

The air admittance valve 30 is located within the interior region 22 such that fluid is diverted around the air admittance valve 30 as it travels along the flow path 24, in use.

In the illustrated embodiment, an axial centre of the air admittance valve 30, an axial centre of the inlet 12 and an axial centre of the outlet 14 are arranged coaxially. In other words, they share a common longitudinal axis A. In alternative embodiments, an axial centre of the air admittance valve 30 may be arranged coaxially with only one of the axial centres of the inlet and outlet 14, 16. In alternative embodiments, an axial centre of the air admittance valve may not be arranged coaxially with either of the axial centres of the inlet and outlet 14, 16.

As will be described in detail below, the straight through fluid trap is configured so that the air admittance valve is in the open state when the flow path 24 is at a negative pressure and to be in the closed state when the flow path 24 is at a non-negative pressure, in use. In this way, when the flow path 24 experiences a negative pressure, the air admittance valve 30 opens which allows air to enter the flow path 24 via the passageway 26, to equalise the pressure in the system. In addition, the air admittance valve 30 does not permit a back flow of air or fluid from the flow path 24 out of the passageway 26. This prevents foul smells from the downstream portion of the flow path 24 being transmitted to the environment surrounding the fluid trap 10.

Referring to Figure 4, the air admittance valve 30 includes a valve seat 32 and a valve member 34 having a seal surface 36 configured for engagement with the valve seat 32 when the air admittance valve 30 is in the closed state. The valve member 34 also has a rear surface 38 on an opposing side of the valve member 34 to the seal surface 36. The rear surface 38 is in fluid communication with the flow path 24, such that a positive or negative pressure in the flow path 24 is communicated to the rear surface 38. In this way, a negative pressure acting on the rear surface 38 causes the seal surface 36 to separate from the valve seat 32, in the direction of arrow B. This provides a fluid communication with the passageway 26 through the housing 20, which allows air to enter the flow path 24 in the direction of arrow C to equalise the pressure.

In the illustrated embodiment, the air admittance valve 30 is an umbrella valve, and the valve member 34 has a stem 44 and a resilient disc 35 connected thereto. The resilient disc 35 defines the seal surface 36 and the rear surface 38. An umbrella valve has been found to be particularly suitable for providing reliable performance of the air admittance valve 30.

In the illustrated embodiment, the seal surface 36 is substantially planar and the rear surface 38 has an angled periphery. In this way, the resilient disc 35 is configured so that the seal surface 36 is biased towards the valve seat 32 when the valve member 34 is fitted to the trap 10 as illustrated. In alternative embodiments, the seal surface 36 and/or rear surface 38 have different shapes (e.g. both may be substantially planar, or both may be angled towards the seal surface 36). In alternative embodiments, the air admittance valve 30 is configured so that the seal surface 36 is biased towards the valve seat 32 when the valve member 34 is fitted to the trap 10 via a different mechanism (e.g. a leaf spring may be provided in or on the resilient disc 35).

A first pressure is communicated to the rear surface 38 and a second pressure is communicated to the seal surface 36 in use. When a pressure differential between the second pressure and the first pressure is greater than a biasing force acting on the resilient disc 35, the resilient disc 35 is configured to resiliently deform away from the valve seat 32 in the direction indicated by arrows B of Figure 4.

In the illustrated embodiment, valve member 34 is located by a first receiving formation 40 in the form of a first boss for receiving the stem 44 of the valve member. In particular, the first boss 40 and stem 44 are configured for interlocking engagement to secure the stem 44 in the first boss 40.

Referring again to Figures 2 and 3, the flow path 24 includes a flow diverter 48 proximal the inlet 12 of the housing 20. The flow diverter 48 is arranged to divert fluid flow towards the outer surface 28 of the housing 20. This directs flow around the air admittance valve 30, which is located in the axial centre of the interior region 22.

In the illustrated embodiment, the flow diverter 48 includes a body having a ridge 94 extending through an axial centre of the housing 20. The ridge 94 extends from a first side of the housing 20 to an opposing side of the housing 20. The flow diverter body also includes two concave surfaces 96 located on opposing sides of the ridge 94 so that, in use, fluid flow is directed away from the axial centre of the housing 20 towards an outer surface 28 of the housing 20. The linear ridge 94 has a first end at a first side of the housing 20 and a second end at the an opposing side of the housing 20, and the width of the linear ridge 94 thickens towards said first and second ends in plan view (e.g. the ridge has a biconcave or "apple core" shape in plan view).

Such a flow diverter shape has been found to optimise the fluid flow rate through the trap 10.

In alternative embodiments the width of the linear ridge 94 may be substantially equal along its length in plan view, or the width of the linear ridge may taper towards the first and second ends of the ridge 94 in plan view.

The flow path 24 further includes a first fluid diversion formation 50 and a second fluid diversion formation 52, as will be described in more detail below. The first and second fluid diversion formations 50, 52 are configured to change the direction of a fluid flow therethrough in use. The first fluid diversion formation 50 is closer to the outlet 14 than the second fluid diversion formation 52, so that a fluid seal is provided between the fluid diversion formations 50, 52 in use. Advantageously, having fluid diversion formations 50, 52 which provide a fluid seal in use prevents foul smells from passing from the outlet 14 to the inlet 12. Since the straight through fluid trap 10 includes an air admittance valve 30, this fluid seal is prevented from being syphoned in the event that a negative pressure is experienced downstream of the fluid diversion formations. In use, this arrangement ensures that debris entering the trap 10 via the inlet 12 does not pass through to the outlet 14, since it accumulates in the first fluid diversion formation 50. In this way, the trap 10 may be emptied and cleaned easily, preventing blockages forming downstream of the trap 10 (which may be more difficult to access to clean/remove).

The flow path 24 includes a dip tube 54 extending in a direction from the outlet 14 of the housing 20 towards the inlet 12 of the housing 20. The dip tube 54 extends from a base end 56 proximal the outlet 14 of the housing 20 towards a tip end 58 distal the outlet 14 of the housing 20. In this way, a first of the fluid diversion formations 50 is provided by the base end 56 of the dip tube 54 and a second of the fluid diversion formations 52 is provided at the tip end 58 of the dip tube 54. Advantageously, this arrangement ensures that a fluid seal is formed between the dip tube 54 and the housing 20, in use.

In the illustrated embodiment, an axial centre of the dip tube 54 is arranged coaxially with the axial centres of the inlet 12, outlet 14 and air admittance valve 30. In other words, they share a common longitudinal axis A. This arrangement is compatible with a substantially tubular straight through housing 20, which provides neatness and compactness.

In alternative embodiments, an axial centre of the dip tube 54 may be arranged coaxially with only one or two of the axial centres of the inlet, outlet and air admittance valve. In alternative embodiments, an axial centre of the dip tube may not be arranged coaxially with any of the axial centres of the inlet, outlet and air admittance valve.

Referring to the embodiment illustrated in Figures 2, 3, 6 and 7, the flow path 24 includes two conduits 60 extending from first conduit ends 62 proximal the flow diverter 48, to second conduit ends 64 proximal the base end 56 of the dip tube 54. This directs fluid to the base of the dip tube 54, which ensures it must undergo two direction changes (i.e. one at the base and one at the tip of the dip tube 54) rather than passing directly through tip of the dip tube 54 and out the outlet 14. In other embodiments, the flow path 24 may include a single conduit 60, or more than two conduits 60 to achieve the same effect.

Each conduit 60 is defined on a first side 60A extending generally radially, a second side 60B extending generally radially, a third side 60C extending generally circumferentially and a fourth side 60D extending generally circumferentially by side walls 61 extending from the first conduit end 62 to the second conduit end 64, such that the conduit 60 defines a substantially tubular passageway.

In the illustrated embodiment, the flow path 24 further includes two channels 66 defined between the first and second sides 60A and 60B of the two conduits 60 (i.e. between the conduits 60). These channels 66 provide a fluid communication between the second conduit ends 64 and the tip end 58 of the dip tube 54. These channels 66 complete the flow path 24 by providing a portion of the flow path 24 which is needed for fluid to pass from the second conduit ends 64 at the base of the dip tube 54 to the tip end 58 of the dip tube 54 (before passing to the outlet 14 through the dip tube 54). Any debris entering the trap 10 via the inlet 12 does not pass through to the outlet 14, since it accumulates around the base of the dip tube 54, rather than passing upwards through the two channels 66. In this way, the trap 10 may be emptied and cleaned easily, preventing blockages forming downstream of the trap 10 (which may be more difficult to access to clean/remove).

In other embodiments, where one conduit 60 is provided, the flow path 24 may include a single channel 66 defined between the first and second sides 60A and 605 of the conduit 60, which achieves the same effects. In other embodiments, where more than two conduits 60 are provided, the flow path 24 may include multiple channels 66 between the first and second sides 60A and 60B of the conduits 60, which achieves the same effects.

In the illustrated embodiment, the distance between the second conduit ends 64 and the tip end 58 of the dip tube 54 is approximately 76mm. This distance provides a fluid seal of suitable depth to provide the advantage of preventing foul smells from passing from the inlet 12 to the outlet 14. In other embodiments, the distance between the second conduit ends 64 and the tip end 58 of the dip tube 54 may be longer or shorter, such as in the range of 30mm to 120mm.

Referring to Figures 2, 3 and 5, the housing 20 includes an upper part 68 defining the inlet 12 and having a first engagement formation 70. The housing 20 further includes a lower part 72 defining the outlet 14 and having a second engagement formation 74. The upper and lower parts 68, 72 are connectable via engagement of the first and second engagement formations 70, 74. In the illustrated embodiment, the first and second engagement formations 70, 74 are complementary threads, but any suitable engagement formations may be used (e.g. an interference fit or apertures for receiving securing fasteners). In this way, the housing 20 may be easily opened to allow access to the components located in the interior region 22. This allows cleaning, replacement of seals or fixing of broken components to be easily carried out.

An interior region of the upper part 68 includes the flow diverter 48, which is arranged to divert fluid flow from the inlet 12 towards the outer surface 28 of the housing 20.

An interior region of the lower part 72 includes the dip tube 54 extending from the base end 56 proximal the outlet 14 of the lower part 72 towards the tip end 58 distal the outlet 14 of the lower part 72.

Referring to Figures 5, 6 and 7, the flow path 24 further includes an internal body 76 located within the interior region 22. The internal body 76 includes the two conduits 60 (which have been described in detail above) and a hollow central region 78 therebetween.

When the straight through fluid trap 10 is assembled (i.e. the internal body 76 and valve member 34 are located between the upper and lower parts 68, 72 which are connected via the engagement formations 70, 74) the dip tube 54 is located within the hollow central region 78 of the internal body 76. In this way, the conduits 60 of the internal body 76 are configured to fit around the dip tube 54. This provides a compact arrangement which minimises the size of the fluid trap 10.

The internal body includes a slot 92 located on a side wall 61 of each conduit 60, between the first and second conduit ends 62, 64. In this way, any fluid or debris that does not enter the conduits 60 at the first conduit ends 62 does not collect between the conduits 60 and the housing 20. Rather, it passes through the slots 92 and into the conduits 60.

The internal body 76 includes a first end 80 located distal the outlet 14 of the lower part 72 (when assembled). This first end SO of the internal body 76 includes the first boss 40 for locating the valve member 34. This allows the valve member 34 to be easily accessed (e.g. for cleaning or replacement) by removing one or both of the upper part 68 and internal body 76.

Referring again to Figure 4, the first end 80 of the internal body 76 and the interior formation 82 of the upper part 68 define an air admittance valve chamber 84 therebetween. The air admittance valve chamber 84 includes a first chamber side 86 in fluid communication with the hollow central region 78 and a second chamber side 88 in fluid communication with the passageway 26. The first chamber side 86 is sealed from the second chamber side 88 via the seal surface 36 of the valve member 34 when the air admittance valve 30 is in the closed state, in use.

Referring to Figure 7, the first end 80 of the internal body 76 includes two apertures 90 defining the fluid communication between the first chamber side 86 and the flow path 24. In this way, the air admittance valve 30 is configured to introduce air to the hollow central region 78 of the internal body 76 (which houses the dip tube 54) when a negative pressure forms in said hollow central region 78 (e.g. via negative pressure being formed in the system, downstream of the dip tube 54). This equalises the pressure, and prevents the water seal surrounding the dip tube 54 from being syphoned down the dip tube 54, which could reduce the ability of the water seal to prevent foul smells from reaching the inlet 12 of the fluid trap 10.

In other embodiments, a single aperture 90 or more than two apertures 90 in the first end of the internal body 76 may be provided, which provides the same effects.

Referring to Figure 8, an alternative straight through fluid trap is indicated at 110. Corresponding features between the straight through trap of Figures 1 to 7 are labelled with the prefix "1".

The main difference between the straight through fluid trap 110 of Figure 8 and the fluid trap 10 of the previous embodiment (Figures 1 to 7) is that the fluid trap 110 does not include an air admittance valve. By omitting the air admittance valve, the trap 110 has less moving parts, which may result in a cheaper manufacturing cost and lower price of the trap. Such a straight through fluid trap 110 may be suitable for installing in a vented plumbing system which does not experience negative pressures.

The straight through fluid trap 110 includes an inlet 112 and an outlet 114. In the illustrated embodiment, an axial centre of the inlet is in line with an axial centre of the outlet. In alternative embodiments, the axial centre of the inlet may be parallel to the axial centre of the outlet.

The straight through fluid trap includes a housing 120 defining an interior region 122. A flow path 124 is provided through the interior region 122 for communication of fluid between the inlet 112 and the outlet 114.

The flow path 124 includes a dip tube 154 extending in a direction from the outlet 114 of the trap 110 towards the inlet 112 of the trap 110. The dip tube 154 extends from a base end 156 proximal the outlet 114 of the trap 110 towards a tip end 158 distal the outlet 114 of the trap 110.

In the embodiment of Figure 8, the flow path 124 also includes two conduits 160 extending from a first conduit end 162 proximal the inlet 114 of the trap 110, to a second conduit end 164 proximal the base end 156 of the dip tube 154. Each conduit 160 is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by side walls 161 extending from the first conduit end 162 to the second conduit end 164, such that the conduit defines a substantially tubular passageway.

The flow path 124 also includes two channels defined by the first and second sides of the conduits 160. Each channel provides a fluid communication between the second conduit end 164 and the tip end 158 of the dip tube 154.

In alternative embodiments, one such conduit 160 and channel or more than two such conduits 160 and channels may be provided.

In the embodiment of Figure 8, the flow path 124 also includes a flow diverter 148 proximal the inlet 114 of the trap. The flow diverter 148 is arranged to divert fluid flow towards the first conduit end 162, in use.

In the embodiment of Figure 8, an axial centre of the dip tube 154 is arranged coaxially with the axial centre of the inlet and outlet. In other words, they share a common longitudinal axis A. This arrangement is compatible with a substantially tubular straight through housing 120, which provides neatness and compactness.

In alternative embodiments, an axial centre of the dip tube 154 may be arranged coaxially with only one of the axial centres of the inlet or outlet.

In the embodiment of Figure 8, the distance between the second conduit ends 164 and the tip end 158 of the dip tube 154 is approximately 76mm. This distance provides a fluid seal of suitable depth to provide the advantage of preventing foul smells from passing from the inlet 112 to the outlet 114. In other embodiments, the distance between the second conduit ends 164 and the tip end 158 of the dip tube 154 may be longer or shorter, such as in the range of 30mm to 120mm.

Referring now to Figures 9 to 14, an alternative straight through fluid trap is indicated at 210. Corresponding features between the straight through traps of Figures 1 to 8 are labelled with the prefix "2", and only differences are discussed.

The difference between the straight through fluid trap 210 of Figures 9 to 14 and the fluid trap 10 of Figures 1 to 7 is that the air admittance valve 230 is a poppet valve rather than an umbrella valve (i.e. the valve member 234 is a poppet).

The poppet 234 is located between first and second poppet receiving formations in the interior region 222. The first poppet receiving formation is arranged to align the poppet on a first side of the seal surface 236 and the second poppet receiving formation is arranged to align the poppet on a second side of the seal surface 236. In this way, the poppet is located at both ends (e.g. between a first and second boss), which prevents misalignment and ensures that seal surface 236 engages and disengages from the valve seat 232 correctly.

In the illustrated embodiment, the poppet 234 has a substantially cross-shaped cross-section defined by a first stem 244 extending orthogonally from the seal surface 236 and a second stem 246 extending orthogonally from the rear surface 238 (the seal surface 236 and rear surface 238 being substantially planar surfaces). The first poppet receiving formation is a first boss 240 in the interior region 222 and the second poppet receiving formation is a second boss 242 in the interior region 222. The first stem 244 of the poppet 234 is located in the first boss 240 and the second stem 246 of the poppet 234 is located in the second boss 242. In this way, the poppet 234 is located at both ends, which prevents misalignment. This increases the reliability and longevity of the valve seal in the closed position.

In alternative embodiments, the poppet 234 may have a substantially H-shaped or T-shaped cross section, or an alternative shape which is complementary to the first and second poppet receiving formations. In this case, the first and second poppet receiving formations may be: larger or smaller bosses than those of the illustrated embodiment; multiple bosses on each side of the seal surface 236 (e.g. for receiving multiple stems extending from the seal surface 236 and or rear surface 238); or any other formation that is complementary to the shape of the poppet 234.

In alternative embodiments, one or both of the seal surface 236 and rear surface 238 may be non-planar surfaces. For example, the seal surface 236 may be dome shaped, for engagement with a complementary valve seat 232.

The internal body 276 includes a first end 280 located distal the outlet 214 of the lower part 272 (when assembled). This first end 280 of the internal body 276 includes the first boss 40 for locating the poppet 34. Referring to Figures 9 and 10, the upper part 268 comprises an interior formation 282 including the second boss 242 for locating the poppet 234. In this way, the poppet 234 of the air admittance valve 230 may be received between the internal body 276 and the upper part 268. This allows the poppet 234 to be easily accessed (e.g. for cleaning or replacement) by removing one or both of the upper part 268 and internal body 276.

Referring to Figure 11, the first end 280 of the internal body 276 and the interior formation 282 of the upper part 268 define an air admittance valve chamber 284 therebetween. The air admittance valve chamber 284 includes a first chamber side 286 in fluid communication with the hollow central region 278 and a second chamber side 288 in fluid communication with the passageway 226. The first chamber side 286 is sealed from the second chamber side 88 via the seal surface 36 of the poppet 234 when the air admittance valve 230 is in the closed state, in use.

In the embodiments of Figures 1 to 7, Figure 8 or Figures 9 to 14, the inlet 12, 112, 212 or outlet 14, 114, 214 may include a telescopic arrangement (not shown on the Figures). In this way, the length of the fluid trap 10, 110, 210 may be easily altered. Advantageously, this provides an easier method of installing the fluid trap 10, 110, 210 (e.g. as a replacement in existing pipework, without having to alter the rest of the pipework).

The straight through trap 10 of Figures 1 to 7, the straight through trap 110 of Figure 8, and the straight through trap 210 of Figures 9 to 14 all include multiple seals 98, 198, 298 arranged such that this traps are configured to withstand back-pressure without leaking, in use. In this way, if a blockage downstream of the trap 10, 110, 210 causes the trap 10, 110, 210 to fill entirely with fluid and debris, the fluid will not leak out of the trap body.

In the illustrated embodiments, the seals include an 0-ring seal 98, 198, 298 between the first engagement formation 70, 170, 270 and the second engagement formation 74, 174, 274 and an 0-ring seal 98, 198, 298 between the internal body 76, 176, 276 and the housing 20, 120, 220. In the embodiments of Figures 1 to 7 and Figures 9 to 14, 0-ring seals 98, 298 arealso provided between the interior formation 82, 282 of the upper part 68, 268 and the first end 80, 280 of the interior body 76, 276.

Referring to Figures 15 and 16, a flow diverter for use within a fluid trap is indicated at 348. The flow diverter includes a body having a linear ridge 394 defining a transverse axis T in plan view. The body also includes two concave surfaces 396 located on opposing sides of said ridge 394 so that, in use, fluid flowing towards the flow diverter 348 in a direction perpendicular to the transverse axis T is directed along the concave surfaces 396 and away from the transverse axis T. In the embodiment of Figures 15 and 16, the linear ridge 394 includes a first end and a second end. The width of the ridge 394 thickens towards the first and second ends in plan view (e.g. the ridge has a bi-concave or "apple core" shape in plan view).

The shape of the flow diverter body illustrated in Figures 15 and 16 has been found to optimise fluid flow over the flow diverter.

In alternative embodiments the width of the linear ridge 394 may be substantially equal along its length in plan view, or the width of the linear ridge may taper towards the first and second ends of the ridge 394 in plan view.

Although the invention has been described in relation to one or more embodiments, it will be appreciated that various changes or modifications can be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet, the straight through fluid trap comprising: a housing defining an interior region; a flow path through the interior region for communication of fluid between the inlet and the outlet; a passageway through the housing from an outer surface of the housing to the interior region; and an air admittance valve located in the interior region; wherein the straight through fluid trap is configured to switch the air admittance valve between an open state, in which the flow path is in fluid communication with said passageway, and a closed state, in which the flow path is isolated from said passageway.
2. A straight through fluid trap according to claim 1, wherein the air admittance valve is located entirely within the interior region defined by the housing, such that the air admittance valve is surrounded by the housing.
3. A straight through fluid trap according to claim 1 or 2, wherein the air admittance valve is located within the interior region such that fluid is diverted around the air admittance valve as it travels along the flow path, in use.
4. A straight through fluid trap according to any of claims 1 to 3, wherein the housing defines a bore and wherein the air admittance valve is arranged within said bore.
5. A straight through fluid trap according to claim 4, wherein the flow path comprises a first portion intended to direct fluid downwards in use and a second portion intended to direct fluid upwards in use, wherein the first and second portions of the flow path are located within said bore, and wherein the air admittance valve is in fluid communication with the first and/or second portions of the flow path.
6. A straight through fluid trap according to any preceding claim, wherein the straight through fluid trap is configured so that the air admittance valve is in the open state when the flow path is at a negative pressure, in use.
7. A straight through fluid trap according to claim 6, wherein the straight through fluid trap is configured so that the air admittance valve is in the closed state when the flow path is at a non-negative pressure, in use.
8. A straight through fluid trap according to claim 7, wherein the air admittance valve comprises a valve seat and a valve member having a seal surface configured for engagement with the valve seat when the air admittance valve is in the closed state.
9. A straight through fluid trap according to claim 8, wherein the valve member comprises a rear surface on an opposing side of the valve member to the seal surface, wherein the rear surface is in fluid communication with the flow path, such that a positive or negative pressure in the flow path is communicated to the rear surface to control the state of the air admittance valve.
10.A straight through fluid trap according to claim 9, wherein the valve member is received in one or more receiving formations in the interior region; optionally, wherein a first receiving formation of the one or more receiving formations is configured to receive a first stem of the valve member; optionally, wherein the first receiving formation and first stem are configured for interlocking engagement to secure the valve member in the first receiving formation.
11.A straight through fluid trap according to any preceding claim, wherein the flow path comprises a flow diverter proximal the inlet of the trap, said flow diverter being arranged to divert fluid flow towards the outer surface of the housing, in use; preferably, wherein the flow diverter comprises a body having a ridge extending through an axial centre of the housing from a first side of the housing to an opposing side of the housing, wherein the body further comprises two concave surfaces located on opposing sides of said ridge so that, in use, fluid flow is directed away from the axial centre of the housing towards an outer surface of the housing.
12.A straight through fluid trap according to any preceding claim, wherein the flow path comprises a first fluid diversion formation and a second fluid diversion formation, said first and second fluid diversion formations being configured to change the direction of a fluid flow therethrough in use (e.g. two 180 degree turns), wherein the first fluid diversion formation is closer to the outlet than the second fluid diversion formation, so that a fluid seal is provided between the fluid diversion formations in use.
13.A straight through fluid trap according to claim 12, wherein the flow path comprises a dip tube extending in a direction from the outlet of the trap towards the inlet of the trap, and wherein the dip tube extends from a base end proximal the outlet of the trap towards a tip end distal the outlet of the trap.
14.A straight through fluid trap according to claim 13 when dependent on claim 11, wherein the flow path further comprises one or more conduits each extending from a first conduit end proximal the flow diverter, to a second conduit end proximal the base end of the dip tube.
15.A straight through fluid trap according to claim 14, wherein each of the one or more conduits is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by one or more side walls extending from the first conduit end to the second conduit end, such that the conduit defines a substantially tubular passageway; optionally, wherein the flow path further comprises one or more channels defined between the first and second sides of the one or more conduits, wherein each of the one or more channels provides a fluid communication between the second conduit end and the tip end of the dip tube.
16.A straight through fluid trap according to any preceding claim, wherein the housing comprises: an upper part defining said inlet and having a first engagement formation; and a lower part defining said outlet and having a second engagement formation; wherein the upper and lower parts are connectable via engagement of the first and second engagement formations (e.g. complementary threads).
17.A straight through fluid trap according to claim 16, wherein an interior region of the upper part comprises a flow diverter arranged to divert fluid flow towards the outer surface of the housing.
18.A straight through fluid trap according to claim 17, wherein an interior region of the lower part comprises a dip tube extending from a base end proximal the outlet of the lower part towards a tip end distal the outlet of the lower part.
19.A straight through fluid trap according to claim 18, wherein the flow path further comprises an internal body located within the interior region, wherein the internal body comprises at least one conduit extending from a first conduit end proximal the flow diveiter, to a second conduit end proximal the base end of the dip tube and a hollow central region therebetween; preferably, wherein the dip tube is located within the hollow central region of the internal body.
20.A straight through fluid trap according to claim 19, wherein the air admittance valve comprises a valve seat and a valve member having a seal surface configured for engagement with the valve seat, wherein a first end of the internal body and an interior formation of the upper part define an air admittance valve chamber therebetween, wherein the air admittance valve chamber comprises a first chamber side in fluid communication with the hollow central region and a second chamber side in fluid communication with the passageway, and wherein the first chamber side is sealed from the second chamber side via the seal surface of the valve member when the air admittance valve is in the closed state, in use.
21.A straight through fluid trap according to claim 20, wherein the first end of the internal body comprises at least one aperture defining the fluid communication between the first chamber side and the flow path.
22.A straight through fluid trap according to any preceding claim, wherein the air admittance valve comprises an umbrella valve.
23.A straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet, the straight through fluid trap comprising: a housing defining an interior region; and a flow path through the interior region for communication of fluid between the inlet and the outlet; wherein the flow path comprises a dip tube extending in a direction from the outlet of the trap towards the inlet of the trap, and wherein the dip tube extends from a base end proximal the outlet of the trap towards a tip end distal the outlet of the trap; wherein the flow path further comprises one or more conduits each extending from a first conduit end proximal the inlet of the trap, to a second conduit end proximal the base end of the dip tube; wherein each of the one or more conduits is defined on a first side extending generally radially, a second side extending generally radially, a third side extending generally circumferentially and a fourth side extending generally circumferentially by one or more side walls extending from the first conduit end to the second conduit end, such that the conduit defines a substantially tubular passageway; and wherein the flow path further comprises one or more channels defined between the first and second sides of the one or more conduits, wherein each of the one or more channels provides a fluid communication between the second conduit end and the tip end of the dip tube.
24.A straight through fluid trap of the kind having an inlet and an outlet wherein an axial centre of the inlet is parallel or in line with an axial centre of the outlet, the straight through fluid trap comprising: a housing defining an interior region; and a flow path through the interior region for communication of fluid between the inlet and the outlet; wherein the housing comprises: an upper part defining said inlet and having a first engagement formation; and a lower part defining said outlet and having a second engagement formation; wherein the upper and lower parts are connectable via engagement of the first and second engagement formations (e.g. complementary threads).
25.A flow diverter for use within a fluid trap, wherein the flow diverter comprises a body having a linear ridge defining a transverse axis and two concave surfaces located on opposing sides of said ridge so that, in use, fluid flowing towards the flow diverter in a direction perpendicular to the transverse axis is directed along the concave surfaces and away from the transverse axis; optionally, wherein the linear ridge comprises a first end and a second end, wherein the width of the linear ridge thickens towards said first and second ends in plan view (e.g. the ridge has a biconcave or "apple core" shape in plan view).