EP3198087A1

EP3198087A1 - Flow restrictor

Info

Publication number: EP3198087A1
Application number: EP15781984.8A
Authority: EP
Inventors: Darren V. WEBB
Original assignee: Polypipe Ltd
Current assignee: Polypipe Ltd
Priority date: 2014-09-25
Filing date: 2015-09-25
Publication date: 2017-08-02
Anticipated expiration: 2035-09-25
Also published as: GB2536400B; ES2812754T3; GB2536400A; WO2016046571A1; GB201416945D0; EP3198087B1

Abstract

A flow restrictor for drainage systems having a body with an aperture through the body through which fluid flows, and a mounting surface for mounting the flow restrictor on or in a drain outlet; and a restrictor portion; wherein said restrictor portion is movable from a first position to a second position in order to restrict fluid flow through the aperture. An alternative flow restrictor has a body comprising a plurality of apertures through the body through which fluid flows, and a mounting surface for mounting the flow restrictor on or in a drain outlet; and one or more restrictor portions; wherein said restrictor portions can be inserted into said apertures so as to limit fluid flow therethrough.

Description

FLOW RESTRICTOR

In the UK, rainwater can be handled either by diverting runoff from buildings into soakaways underground, into water harvesting tanks or by diverting the runoff directly into the sewer system.

Due to the age of the UK sewer system, current building regulations in the UK may include limits on levels of runoff water. For example, one criterion of new construction projects is that they may not be allowed to increase the rate at which water is discharged into public sewers compared to the pre-existing site. Thus, the sewers are protected from spikes in water flow due to new constructions.

These regulations may be met by reducing hard landscaping and promoting natural drainage, or by providing temporary storage tanks which regulate the flow over a longer period and thus reduce the peak flow rates. In locations where large tanks are not possible, one alternative has been to use flat roofs as a temporary storage tank by limiting the rate of water runoff from the roof. These are commonly known as blue roofs. In blue roofs, the roof is designed to be substantially flat and is provided with a number of outlets connected to the drain, through which the runoff water flows. The outlets may be designed so that the maximum rate of water leaving the roof is not in excess of the legal restriction. Since this is usually less than the rate at which the rain fills the blue roof, the water builds up gradually. Overflow pipes may be provided in order to ensure that the roof does not become overloaded and prevent any structural damage from the weight of the water. While the system is effective in regulating flow output from the roof, it requires careful planning to ensure that the flow rate through the provided outlets is neither too great, thereby negating the effects of the blue roof, nor too low, and causing water to build up too quickly and be diverted through the overflow pipes.

A further measure to reduce runoff rate is the use of green roofs, or living roofs, which are covered with a layer of vegetation over a waterproofing membrane. Commonly this involves a layer of soil in which grasses, mosses and other plants may be grown, which absorbs rainwater and provides additional insulation to the building. Green roofs can also be used in combination with blue roofs, e.g. areas of the roof may be discrete, or the soil and vegetation layer may be raised from the surface of the roof so that the area below the green layer may act as a drainage layer or as water store as in a more conventional blue roof.

UK patent application GB2502515 describes a flow restrictor that can be inserted into a conventional drain outlet with a narrow channel for limiting the water flow into the drain system. A range of inserts are provided with varying channel widths. The flow restrictor is then fitted with an insert with a desired channel width in order to provide a degree of adaptability to the unit. However, the inserts must either be sold separately, or a range of inserts must be provided with each unit.

It is an aim of the present invention to provide a flow restrictor which mitigates or ameliorates at least one of the problems of the prior art, or provides a useful alternative.

According to a first aspect of the invention there is provided a drain flow restrictor, comprising:

a body comprising an aperture through the body, through which fluid flows, and a mounting surface for mounting the flow restrictor on or in a drain outlet; and a restrictor portion; wherein

said restrictor portion is movable from a first position to a second position in order to restrict fluid flow through the aperture. The flow restrictor according to the first aspect allows at least two different rates of fluid flow without requiring any additional components or parts. In one configuration the restrictor portion is in the first position and fluid may flow at a first rate. In a second configuration, the restrictor portion is in the second position and the fluid flow is restricted to a second rate, less than the first. Thus, two rates of flow are attainable with a single flow restrictor.

The restrictor portion may restrict fluid flow through the aperture by restricting the size of the aperture e.g. by blocking or sealing at least part of the aperture. The aperture defines a flow path through the body through which fluid can travel. In one embodiment, the restrictor portion reduces the cross-sectional area of the flow path through the aperture. Cross-sectional area is intended to mean the area in the plane perpendicular to the flow path. The restrictor portion may be movable through multiple positions, for example, to provide multiple restriction levels. The first position may correspond to the position wherein maximum permitted fluid flow through the aperture is achieved. For example, the first position may comprise the position wherein the cross-sectional area of the aperture is at a maximum. In one embodiment, in the first position the restrictor portion may not restrict, or substantially not restrict the fluid flow. E.g. the restrictor portion is not blocking or sealing the aperture, or substantially not blocking or sealing the aperture. Alternatively, the first position may comprise any position wherein the permitted fluid flow rate through the aperture is greater than the second position. For example, the first position may comprise any position wherein the cross-sectional area of the fluid path is greater than in the second position.

The second position may correspond to the position wherein a minimum fluid flow through the aperture is permitted. In one embodiment, the restrictor portion may restrict, or substantially restrict all fluid flow through the aperture when in the second position. E.g. the restrictor portion may block or seal the aperture, or may substantially block or seal the aperture. Alternatively, the second position may comprise any position wherein the permitted fluid flow rate through the aperture is lesser than the first position. For example, the second position may comprise any position wherein the cross-sectional area of the fluid path is lesser than in the first position. The flow restrictor may comprise any number of intermediate positions between the first and second positions. The intermediate positions may allow varying levels of fluid flow through the aperture. In one embodiment, the intermediate positions may be continuous from the first to the second position. In one embodiment, the intermediate positions may comprise a series of defined positions, for example, regularly spaced between the first and second positions.

The present invention is therefore more adaptable than those known in the prior art. In some embodiments, the flow restrictor may comprise only two parts. Thus, there are fewer parts to manufacture and thus manufacturing and shipping costs are reduced. Furthermore, since there are no interchangeable parts or inserts, there is less wastage caused by loss of parts or by the necessity to provide multiple redundant inserts with each unit. The flow restrictor is also more desirable for users, since there is no need to purchase and install multiple different sizes of flow restrictor and the flow rate may be adjusted or configured after the flow restrictor has been installed. Instead, they can purchase multiple copies of a single unit and adjust the flow rates to suit the specific application. Furthermore, since the flow rate is selected by the position of the restrictor portion, there is no need for additional parts, inserts or specialist tools.

The flow restrictor may be configured to fit in a conventional drain outlet. For example, the flow restrictor may be circular. The flow restrictor may comprise an angled or chamfered surface. In one embodiment, the body is frusto-conical. The angled or chamfered surface and/or the angled face of the frusto-conical body may be configured to fit with a similarly angled, chamfered and/or frusto-conical drain outlet. This design is advantageous since it can be used with varying sizes of drain outlet without requiring modification.

Additionally or alternatively, the mounting surface may comprise a stepped portion designed to sit on a cooperating surface of a drain outlet. In one series of embodiments, the restrictor portion is rotatably movable relative to the body. For example, the restrictor portion may be rotated from the first position to the second position. In one embodiment, the restrictor portion may be connected to the body by way of a pivot means, e.g. a pin or rivet. The restrictor portion may be rotatable about the pivot means.

In one embodiment, the body may comprise an overflow aperture. The overflow aperture may be positioned in the centre of the body, e.g. the overflow aperture may extend from the centre of a first face to the centre of a second face of the body. The overflow aperture may receive an overflow pipe. The overflow aperture may define an overflow path through which fluid can pass.

In one series of embodiments, the restrictor portion may comprise a projection received within and/or extending through the overflow aperture. The projection may abut the inner surface or edge of the overflow aperture. The projection may be rotatable within the overflow aperture such that it forms a pivot about which the restrictor portion may rotate. The first aperture may be arcuate and positioned radially around the overflow aperture, e.g. the two apertures may be coaxial.

The projection may be cylindrical. The projection may comprise an open first end and a closed second end, or it may comprise a pair of open ends. The projection may be configured for provide a form interlock with the body, in order to inhibit the body and restrictor portion becoming detached. For example, the projection may comprise a concentric channel in its outer surface for cooperating with a projecting ridge provided on the inside of the overflow aperture. The concentric channel may be segmented, for example, to provide an interlock with a different strength to a continuous channel. In embodiments wherein the projection comprises a closed end, the closed end face may be provided with a drill location means at the centre thereof.

The projection may be housed within the overflow aperture and receive an overflow pipe e.g. so as to provide an overflow path through both the projection and the overflow aperture through which fluid can pass. The closed end of the projection may be removed by a user, e.g. by drilling through the centre, so as to permit fluid flow through the projection. The overflow pipe may extend beyond the upper surface of the body and/or restrictor portion. The length of the overflow pipe may determine the maximum water level permitted in a blue roof or water attenuation tank.

The flow restrictor may comprise one or more indexing means for indicating the first and/or second position, and/or any number of intermediary positions. The indexing means may comprise one or more detents, grooves and a complementary projection or vice versa, or visual identifiers, for example, to assist the user in setting the desired level of flow rate through the aperture. For example, the indexing means may comprise a groove on either of the body or the restrictor portion, and a tooth on the other of the body or the restrictor portion. The groove may comprise a pair of adjacent ridges with a groove positioned between. The tooth and groove or grooves may cooperate so as to interlock e.g. in use, the tooth may be loosely held in the groove so as to restrict movement of the restrictor portion relative to the body. The indexing means may provide a level of resistance that can be felt by the user when moving the restrictor portion, but would not prevent movement beyond the indexing means. The flow restrictor may further comprise a screw clip and/or a screw hole, e.g. on the restrictor portion. The screw clip may be configured to hold a screw or bolt. The restrictor portion may be moved into its desired position and fixed in place by inserting the screw or bolt through the screw hole and either into or through the body. The screw clip therefore provides a simple way to ensure that the screw or bolt is not lost during transit, and is in the right location when the flow restrictor is being positioned.

According to a second aspect of the invention, there is provided a drain flow restrictor comprising:

a body comprising a plurality of apertures through the body, through which fluid flows, and a mounting surface for mounting the flow restrictor on or in a drain outlet; and

one or more restrictor portions; wherein

said restrictor portions can be inserted into said apertures so as to limit fluid flow therethrough.

In one embodiment, the apertures are all identical in size and shape. In a further series of embodiments, the apertures may be different sizes. For example, the body may be provided with one or more first apertures, and one or more second apertures, larger than the first. The restrictor portions may be more than one size. For example, the restrictor portions may be configured to fit into either a first, or a second aperture. The restrictor portions may be colour coded, for example, to indicate variation in size and/or shape. By inserting a restrictor portion into the body, the number and/or size of the apertures may be reduced. For example, the apertures define the fluid path through the drain flow restrictor, and inserting one or more restrictor portions limits the cross sectional area of the fluid path through the body. In one embodiment, the restrictor portion may completely preclude fluid flow through the aperture into which it is inserted.

The restrictor portions may comprise removable inserts. The inserts may comprise a body and a head portion, wherein the head portion extends beyond the edge of the aperture into which it is inserted. For example, the inserts may have a T-shaped cross- section, wherein the head portion abuts the surface of the body. The head portion may therefore provide a fluid resistant seal. The restrictor portions may comprise a plastic or rubber material. For example, the restrictor portions may comprise PVC or HDPE.

The restrictor portions may be held in position by an interference fit, frictional fit and/or snap-fit. For example, the restrictor portion may slot in to the apertures without requiring any further attaching means. Alternatively, the restrictor portions may comprise teeth or lugs which clip into a corresponding groove, hole, channel or depression in the side of the aperture, or vice versa. In one embodiment, the restrictor portions are held in place by friction with the aperture, e.g. where the restrictor portions are made from a rubber material. For example, the rubber material may be compressed slightly upon insertion, so as to ensure a tight seal within the aperture.

The body may comprise a flat surface. The apertures may be regularly spaced around the body, for example in a repeating pattern. In one embodiment, the apertures are arranged in concentric rings.

The body may be fully housed within a drain outlet and/or it may comprise an upper surface of a drain outlet. In one example, the body comprises a roof portion of a drain outlet.

The drain flow restrictor may comprise an overflow aperture. The overflow aperture may be configured to receive an overflow pipe, which extends away from the surface of the body to provide an overflow flow path with an opening positioned, in use, above the body. The overflow aperture may have a circular cross section, for example for receiving a cylindrical overflow pipe.

The drain flow restrictor may comprise a combination of apertures and restrictors according to the first and second aspects of the invention. According to a third aspect of the invention, there is provided a drain outlet comprising the flow restrictor according to the first and/or second aspect of the invention.

The drain outlet may comprise an outlet body with a pair of open ends, a connecting portion adjacent the smaller of the open ends for connecting to a drain or pipe and a mounting surface for receiving the mounting surface of the flow restrictor. The mounting surface may be frusto-conical and/or it may comprise a stepped portion, depending on the mounting surface of flow restrictor. The drain outlet may be frusto- conical so as to funnel water towards the connecting portion. In one embodiment, the drain outlet may further comprise a flat roof portion. The flat roof portion may sit within the outlet body and comprise a flat surface in substantially the same plane as the uppermost open end of the outlet body. The flat roof portion may comprise a series of holes or channels to act as a filter so that water may flow through the roof portion but prevent solid objects from entering the outlet body. The flat roof portion may be strong enough to hold the weight of a person standing on the outlet roof. In one embodiment, the roof portion may comprise a drain flow restrictor according the second aspect of the invention.

In an alternative embodiment, the drain outlet may further comprise a domed roof portion. The domed roof portion may extend beyond the uppermost open end of the outlet body. The domed roof portion may comprise a series of holes or channels so as to act as a filter and prevent solid objects from entering the outlet body. The domed roof portion may be curved, for example a hemi-sphere, spherical segment, or irregular curve. Alternatively, the domed roof portion may be cylindrical, conical or frusto-conical.

The drain outlet may further comprise an overflow pipe. For example, the drain outlet may comprise a pipe received within a projection and/or overflow aperture on the flow restrictor. The overflow pipe may extend from the uppermost surface of the flow restrictor and/or the uppermost surface of the outlet body. In one embodiment, the drain outlet comprises a domed roof portion and an overflow pipe, wherein the overflow pipe is housed within the domed roof portion. The overflow pipe may extend a distance corresponding to the maximum depth of water permitted on a blue roof, green roof and/or a water attenuation tank. In use, the drain outlet is installed and the flow restrictor is set to permit the desired flow rate through the outlet by moving the restrictor portion to the desired position relative to the body. When it rains, the water flows through into the drain outlet and through the aperture into the drain system. During heavy rainfall, the rate at which water flows through the aperture may be less than the rate at which the blue roof, green roof or water attenuation tank fills. Thus, the depth of water above the flow restrictor slowly increases. In embodiments where an overflow pipe is installed, when the water level exceeds the height of the overflow pipe, the water flows through the overflow pipe and through an overflow aperture in addition to flowing through the first aperture. Thus the flow rate through the flow restrictor is increased.

According to a fourth aspect of the invention, there is provided a drainage system comprising at least one drain outlet according to the third aspect of the invention.

The drainage system may comprise a blue roof, green roof, water attenuation tank and/or any other suitable form of water attenuator or combination thereof, at least one drain outlet according to the third aspect of the invention, and at least one pipe connecting the drain outlet to a municipal drain or soakaway.

In one series of embodiments, multiple drain outlets according to the second aspect on the invention are provided. The flow restrictors may be configured to permit varying flow rates. Additionally or alternatively, one or more of the multiple drain outlets may comprise overflow pipes. In embodiments with more than one overflow pipe, the flow rates through the overflow pipes may be different depending on the diameter of the pipe and/or the diameter of the second aperture. For example, holes drilled through the closed end of the projection may vary in size depending on the desired flow rate through the overflow pipe.

The overflow pipes may be of varying length so as to permit fluid flow through a first overflow pipe prior to permitting fluid flow through a second overflow pipe. The overflow pipes may be configured to provide a gradual increase in capacity (i.e. flow rate) as the depth of water on the blue roof, green roof and/or in a water attenuation tank increases. This may be advantageous where the first overflow pipe is configured to permit water flow prior to the maximum water level being reached. This may allow water to flow at an increased rate, but still below the rate at which water fills the tank, so as to reduce the rate at which the tank fills.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying figures, in which:

Figure 1 is a perspective drawing of the flow restrictor according to the first aspect; Figure 2 is a plan view from above showing the flow restrictor in the first position;

Figure 3 is 2 is a plan view from above showing the flow restrictor in the second position;

Figure 4 is a section through the line X-X;

Figure 5 is a plan view from above showing a drain outlet according to the third aspect of the invention;

Figure 6 is a section through the line Y-Y;

Figure 7 is a section through the line Y-Y of an alternative embodiment of the third aspect;

Figure 8 is a perspective drawing of a flow restrictor according to the second aspect of the invention;

Figure 9 is a section through the line Z-Z of Figure 8; and

Figure 10 is a perspective view showing a further embodiment of the first aspect of the invention.

Turning now to Figure 1 , there is shown an embodiment of the flow restrictor according to a first aspect of the invention. The flow restrictor 1 has a body 2 with an aperture 3 extending therethrough and a restrictor portion 4 on the upper surface of the body 2. The body 2 is disc shaped with an angled surface, with a series of indentations 5 in its outer edge in order to fit around screw holes in a drain outlet (not shown). The angled surface of the body 2 forms the mounting surface 6.

The body 2 comprises a second aperture 7 in the centre thereof, through which a cylindrical projection 8 extends and is held. The cylindrical projection 8 is part of the restrictor portion 4, and acts as a pivot around which the restrictor portion 4 can rotate. Depending on the direction of rotation of the restrictor portion 4, the first aperture 3 is progressively covered or exposed so as to increase its surface area and thereby adjust the flow rate of water through the aperture 3.

The facing surfaces of the body 2 and restrictor portion are provided with a series of indexing means 9 arranged at regular intervals around its outside edge. The indexing means 9 comprise a pair of teeth with ramps 9a on either side and a groove 9b in between. The restrictor portion 4 has a tab 10 extending radially outwardly so that, as the restrictor portion 4 rotates, only the tab 10 passes over the indexing means 9. The surface of the tab 10 facing the body has an additional tooth (not shown) which interacts with the indexing means 9 by riding up the ramps 9a to sit in the groove 9b. This provides an easy mechanism by which defined positions for the restrictor portion 4 may be located by a user, and which are easily visible and/or felt. The upper surface of the body 2 also has a ridge 14 running concentrically with the restrictor portion 4. The ridge 14 serves two purposes: firstly, by running concentrically with the restrictor portion it provides a seal where the two parts abut so as to prevent water from running around the restrictor portion; and secondly, it provides a hard stop preventing the over rotation of the restrictor portion 4 by abutting the tab 10 when the restrictor portion 4 is in the first position A and the second position B.

The restrictor portion 4 is also provided with a screw holder 1 1 , screw 12 and screw hole 13. When the user has rotated the restrictor portion 4 to the desired position, the screw 12 may be removed from the holder 1 1 and screwed through the screw hole 13 into the body 2. The restrictor portion 4 is thus locked in position relative to the body 2 so that it cannot become accidentally dislodged during operation (for example by a piece of debris etc.) and change the flow rate through the flow restrictor 1. If the user wishes the change the flow rate for any reason, they can simply unscrew the screw 12, rotate the restrictor portion 4 to a new position, and then re-insert the screw 12 through the screw hole 13 into a new part of the body 2. When the body is produced from plastic, for example HDPE, PVC or similar, the screw may be screwed directly into the body without requiring a screw hole to be pre-drilled. In embodiments made from stronger materials, such as aluminium, screw holes may be required to be drilled by the user, or even pre-drilled during manufacture, adjacent each indexing means. Alternatively, the screw may be replaced with a bolt and can thus be bolted in place. Holes running through the body would be too small to affect the flow rate running through the flow restrictor.

Turning now to Figure 2, the restrictor portion 4 is shown in the first position A. The restrictor portion 4 is fully rotated (i.e. further rotation is prevented by the ridge 14) to give the aperture 3 the largest attainable cross-sectional area. This corresponds with the greatest flow rate through the aperture 3. The tab 10 is abutting a first end 14A of the ridge 14. Turning now to Figure 3, the restrictor portion 4 is shown in the second position B. The restrictor portion 4 is fully rotated in the opposite direction to that shown in Figure 2, so as to restrict flow through the majority of the aperture 3. The tab 10 is abutting a second end 14B of the ridge 14. In this embodiment, when the restrictor portion 4 is in the second position B, the aperture 3 is not fully obstructed, and thus a small area is still exposed. Due to the size of the exposed aperture 3, the flow rate in the second position B is very low and is the minimum flow rate.

Referring now to figures 2 and 3, the projection 8 also has a drill guide 15 in the centre of the base of the projection 8. If a user wishes to fit an overflow pipe to the flow restrictor 1 , the user drills out the base of the projection 8 and inserts the overflow pipe into the projection (see Figure 7). The overflow pipe provides an alternative flow path for water to flow though the projection 8 and thus through the second aperture 7. Turning now to Figure 4, the flow restrictor 1 is shown in cross-section through the line X-X of Figure 3. More clearly shown is the frusto-conical shape of the body 2, with the mounting surface 6 formed by the angled surface. In use, the flow restrictor 1 can be simply placed in a drain outlet (not shown) if the angle of the restrictor 1 matches that of the outlet. In applications with drain outlets of differing angle or shape (for example, if retrofitting a roof to act as a blue roof) the flow restrictor may sit within an adaptor or spacer (not shown).

Also shown is the interlock joining the body 2 and the restrictor portion 4. The body 2 has a lip 16 running around the internal face of the second aperture 7. The lip 16 fits within a groove formed between a corresponding ridge 17 of the projection 8 and the upper surface 18 of the restrictor portion 4, which extends over the body around the circumference of the second aperture. To connect the body 2 and the restrictor portion 4, the projection 8 is inserted through the second aperture 7 until the lip 16 on the body rides over the corresponding ridge 17 on the projection and sits in the groove formed between the ridge 17 and the upper surface 18 to form an interlock. To disconnect the body and the restrictor portion, the resistance caused by the ridge must be overcome, thereby providing a strong connection between the two components. Since the interlocking parts are both circular, it permits them to rotate relative to one another while remaining sealed i.e. to allow the restrictor portion 4 to rotate about the second aperture 7 and adjustably block off the first aperture 3. Turning now to Figures 5 to 6, there is shown a drain outlet according to an embodiment of the invention. The drain outlet 20 is made up of a frusto-conical outlet body 21 with an open upper end 22 and lower end 23. The lower end terminates in a connecting portion 24 which can be attached to a drain pipe or similar. The internal face of the frusto conical body 21 forms a mounting surface 25 on which a flow restrictor 1 is housed. Above the flow restrictor, a flat roof portion 26 is housed within the outlet body 21. The flat roof portion 26 has a flat upper surface 27 and a mounting surface 28 for mounting onto the inner surface of the outlet body. Flat roof portion 26 also has a series of screw holes 29 into which screws 30 can be inserted to securely hold the roof portion 26 to the outlet body 21 and sandwich the flow restrictor 1 in between. The open upper end 22 of the body 21 extends into flange portion 29 which are provided with further screw holes 34. The flange extends around the circumference of the outlet body 21 so as to connect the outlet to the surface of a blue roof or attenuation tank (not shown).

Figure 7 shows an alternative embodiment of the third aspect, wherein like parts will not be further described. The flat roof portion 26 shown in Figure 5 and 6 has been replaced with a domed roof portion 32, which extends upwardly from the upper surface of the outlet body 21. Both domed roof portion 32 and flat roof portion 26 are provided with multiple holes and slits 31 through which water can flow but which act as a crude filter to prevent large objects blocking the flow restrictor. Both roof portions 26, 32 protect the flow restrictor from adjustment or accidental damage.

The extra height of the domed roof portion 32 means there is a larger gap between the uppermost surface of the flow restrictor 1 and the inside of the roof. Thus this design permits the use of an overflow pipe 33 which is housed within the projection 8. The base of the projection 8 has been removed in order to permit water to flow through the overflow pipe 33 and thus through the second aperture 7. The overflow pipe 33 extends beyond the uppermost surface of the body 21 by height H. The height H can be varied by using longer or short overflow pipes. The greater the height H, the greater the depth of water that can build up on the blue roof or tank. Thus the height H provides a control to prevent the maximum weight on the roof being exceeded, for example, if the first aperture becomes blocked or if the rainfall is exceedingly heavy. Turning now to Figures 8 and 9, there is shown an exemplary embodiment of the flow restrictor according to the second and third aspects of the invention. The drain flow restrictor 50 has a body 51 , through which multiple apertures 52, 53 extend. The apertures 52, 53 are arranged in concentric rings, with first apertures 53 arranged in the inner circle and the second, larger apertures arranged in an outer ring. There are six first apertures 52 and six second apertures 53 in total, although this may vary according to requirement. It is envisaged that further sizes of aperture could be provided, for example in an additional outer circle, for situations where larger flow rates are required and larger drain outlets available.

The apertures 52, 53 are arcuate, with approximately square ends. This arrangement allows for close packing of the apertures 52, 53, without compromising the strength of the upper surface.

Selected apertures 52, 53 are provided with restrictor portions 54, 55, which slot into the aperture. The restrictor portions are inserts 54, 55 produced from a flexible rubber compound so that they may be compressed slightly upon insertion to provide a strong frictional fit within the apertures. The first inserts 54 are of a suitable size to prevent fluid flow through first apertures 52, and second inserts 55 are of a suitable size to prevent fluid flow through second apertures 53. In an alternative embodiment (not shown) the restrictor portions 54, 55 are produced from a plastics material such as PVC or HDPE and provided with one or more protruding lugs for providing a 'snap-fit' within a corresponding formation within the apertures 52, 53. The snap-fit may be sufficient to prevent the restrictor portions being removed from the apertures 52, 53.

The body 50 is also provided with an overflow aperture 58 in the centre of the body 51. In the overflow aperture 58, is provided a pipe holder 59 and an overflow pipe 60. The pipe holder 59 is provided with a similar lip and groove arrangement 16, 17, 18 as the rotating restrictor portion 4 shown in Figure 4. The inner surface of the pipe holder 59 is cylindrical in order to hold an overflow pipe 60 in a friction fit. The overflow pipe 60 extends above the uppermost surface by a pre-selected distance corresponding with a predetermined acceptable depth of water. In this embodiment, the body 50 forms the roof portion of a drain outlet 70 with a body 21A, wherein like parts have not been further described. The body 50 is also provided with a series of screw holes 56 through which screws 57 are inserted to connect the body 50 to the drain outlet body 21A.

In use, when a blue or green roof or a water attenuation tank is installed, the installer is able to fit the drain outlet 70 and then adjust the flow rate through the drain outlet 70 by selectively inserting inserts 54, 55 into the apertures 52, 53. Where a high flow rate is desired, fewer of the apertures 52, 53 will be blocked with inserts 54, 55.

It is also possible for the inserts 54, 55 to be used in combination with the drain outlet pictured in Figures 5 and 6, since the holes in the roof portion are designed to be the same size. The whole system is therefore highly adaptable and may be configured to suit many applications.

Turning now to Figure 10, there is shown a further embodiment of the first aspect of the invention. The flow restrictor 1A is largely similar to the flow restrictor 1 as shown in Figures 1 to 4, and has a body 2A with a restrictor portion 4A rotatably mounted thereto. The difference between flow restrictor 1 and flow restrictor 1A lies in the interlock between the cylindrical projection 8A and the upper surface 18A.

Rather than the continuous upper surface 18 shown in Figure 1 , the cylindrical projection 8A is surrounded by segmented region 19A, which extends around the perimeter of the cylindrical projection 8A and joins the upper surface 18A. The segmented region 19A is formed of connection segments 71 , which have a cross- section identical to that shown in Figure 4 to provide a snap fit as described above. Alternately spaced between connection segments 71 are spacers 72. Spacers 72 are apertures in the upper surface 18A, which do not provide a snap-fit arrangement. There is a ridge (not shown) which runs around the cylindrical projection, similar to the ridge 17 of Figure 4. The ridge may be continuous, like the ridge 17, or optionally it may also be segmented.

By providing a segmented region 19A, the strength of the snap-fit connection between body 2A and restrictor portion 4A can be configured depending on the number and relative area of the connection segments 71 and spacers 72, without affecting the ability to rotate the body 2A and restrictor portion 4A relative to one another.

Claims

CLAIMS:

1. A drain flow restrictor, comprising:

a body comprising an aperture through the body, through which fluid flows, and a mounting surface for mounting the flow restrictor on or in a drain outlet; and

a restrictor portion; wherein

said restrictor portion is movable from a first position to a second position in order to restrict fluid flow through the aperture.

2. The drain flow restrictor according to claim 1 , wherein in a first configuration the restrictor portion is in the first position and fluid flows at a first rate and in a second configuration the restrictor portion is in the second position and the fluid flow is restricted to a second rate, less than the first.

3. The drain flow restrictor according to any one of the preceding claims wherein the first position corresponds to the position wherein maximum permitted fluid flow through the aperture is achieved.

4. The drain flow restrictor according to claim 3 wherein the first position comprises the position wherein the cross-sectional area of the aperture is at a maximum.

5. The drain flow restrictor according to any one of the preceding claims wherein the second position corresponds to the position wherein a minimum fluid flow through the aperture is permitted.

6. The drain flow restrictor according to any one of the preceding claims, wherein the flow restrictor comprises at least one intermediate position between the first and second positions.

7. The drain flow restrictor according to claim 6, comprising a plurality of intermediate positions, wherein said intermediate positions are regularly spaced between the first and second positions.

8. The drain flow restrictor according to claim 6, comprising a plurality of intermediate positions, wherein said intermediate positions extend continuously from the first to the second position.

9. The drain flow restrictor according to any one of the preceding claims, wherein the flow restrictor comprises only two parts.

10. The drain flow restrictor according to any one of the preceding claims, wherein the mounting surface comprises an angled or chamfered surface.

1 1. The drain flow restrictor according to any one of the preceding claims, wherein the restrictor portion is rotatably movable relative to the body.

12. The drain flow restrictor according to claim 1 1 , wherein the restrictor portion is connected to the body by way of a pivot means and said restrictor portion is rotatable about the pivot means.

13. The drain flow restrictor according to any one of the preceding claims, further comprising an overflow aperture.

14. The drain flow restrictor according to claim 13, wherein the overflow aperture extends from the centre of a first face to the centre of a second face of the body.

15. The drain flow restrictor according to either claim 13 or claim 14, wherein the first aperture is arcuate and positioned radially around the overflow aperture.

16. The drain flow restrictor according to any one of claims 13 to 15, wherein the restrictor portion comprises a projection received within and/or extending through the overflow aperture.

17. The drain flow restrictor according to claim 16, wherein the projection is rotatable within the overflow aperture such that it forms a pivot about which the restrictor portion may rotate.

18. The drain flow restrictor according to either claim 16 or 17, wherein the projection is configured to provide a form interlock with the body, in order to inhibit the body and restrictor portion becoming detached.

19. The drain flow restrictor according to claim 18, wherein the projection comprises a concentric channel in its outer surface for cooperating with a projecting ridge provided on the inside of the overflow aperture.

20. The drain flow restrictor according to claim 19, wherein the concentric channel is segmented.

21. The drain flow restrictor according to any one of claims 16 to 20, wherein the projection comprises a closed end face, and said closed end face comprises a drill location means at the centre thereof.

22. The drain flow restrictor according to any one of the preceding claims, comprising one or more indexing means for indicating the first and/or second position, and/or any number of intermediary positions.

23. The drain flow restrictor according to claim 22, wherein the indexing means comprises one or more detents, grooves and a complementary projection or vice versa, or visual identifiers.

24. The drain flow restrictor according to any one of the preceding claims, comprising a screw clip and/or a screw hole.

25. A drain flow restrictor, comprising:

one or more restrictor portions; wherein

26. The drain flow restrictor according to claim 25, wherein the body comprises one or more first apertures, and one or more second apertures, larger than the first.

27. The drain flow restrictor according to either claim 25 or 26, wherein the restrictor portions are colour coded to indicate variation in size and/or shape.

28. The drain flow restrictor according to any one of claims 25 to 27, further comprising an overflow aperture and an overflow pipe received within said overflow aperture, wherein said overflow pipe extends from the surface of the body.

29. The drain flow restrictor according to any one of claims 25 to 27, wherein the body also forms a roof portion of a drain outlet.

30. A drain outlet comprising a flow restrictor according to any one of the preceding claims.

31. A drain outlet according to claim 30, comprising an outlet body with a pair of open ends, a connecting portion adjacent the smaller of the open ends for connecting to a drain or pipe and a mounting surface for receiving the mounting surface of the flow restrictor.

32. The drain outlet according to either claim 30 or 31 , further comprising a flat roof portion.

33. The drain outlet according to either claim 30 or 31 , further comprising a domed roof portion.

34. The drain outlet according to any one of claims 30 to 33, comprising an overflow pipe.

35. A drainage system comprising at least one drain outlet according to any one of claims 30 to 34.

36. The drainage system according to claim 35, comprising a water attenuation tank and/or a blue roof, at least one drain outlet according to any one of claims 30 to 34, and at least one pipe connecting the drain outlet to a municipal drain or soakaway.

37. A drain flow restrictor substantially as described herein and with reference to the accompanying drawings.