GB2374352A

GB2374352A - Grease trap

Info

Publication number: GB2374352A
Application number: GB0207023A
Authority: GB
Inventors: John Francis Concannon; Sean Gerard Dunleavy
Original assignee: Rodicon Ltd
Current assignee: Rodicon Ltd
Priority date: 2001-03-27
Filing date: 2002-03-25
Publication date: 2002-10-16
Anticipated expiration: 2022-03-25
Also published as: GB0207023D0; GB2374352B; IE20020215A1; IES20020216A2

Abstract

A grease trap (1) comprises a housing (2) which defines a hollow interior region (10), which in turn is divided into an upstream chamber (17), a downstream chamber (18) and a riser chamber (19) intermediate the upstream and downstream chambers (17,18) by an upstream partition (14) and a downstream partition (15). An upstream inlet port (11) delivers waste water with entrained grease into the upstream chamber (17), and an outlet port (12) delivers waste water with the entrained grease removed from the downstream chamber 18. Waste water passes from the upstream chamber 17 through a communicating opening (20) in the upstream partition (14), and in turn rises in the riser chamber (19), and flows over an interior weir (23) into the downstream chamber (18). An outlet opening (28) from the downstream chamber (18) delivers waste water from which solids and entrained grease have been removed through a riser (29) and in turn through the outlet port (12). Sludge collecting containers (33,34) are located in the upstream and downstream settling chambers (17,18) for collecting entrained solids in the waste water. Entrained grease in the waste water settles out of the water in the upstream and downstream chambers (17,18) and floats on the surface thereof for collection and removal by the sludge containing containers (33,34) as they are being removed through inspection openings (37,38), respectively.

Description

"A grease trap" The present invention relates to a grease trap, and in particular, to a grease trap for a waste water system, for example, an underground waste water system from a commercial establishment, such as a hotel, a restaurant or the like, or a domestic dwelling, a group of domestic dwellings, although needless to say the grease trap may be used in any situation in which it is desired to collect grease and other fats and solids which rise to the surface of a settling or settled liquid from waste water or other waste liquid.

Grease traps are typically used in waste water systems from hotels, restaurants, industrial premises, as well as in domestic waste water systems and are provided downstream of a water trap which receives waste water from an outlet drain, for example, from a kitchen sink or other sink or appliance where grease and other fats are likely to be entrained in the waste water. Such grease, typically is of the type used in cooking, for example, frying, and when cooled solidifies and floats to the surface of the water. It is desirable that grease entrained in waste water should be collected as close to source as possible to avoid fouling drains, which can subsequently lead to blockage of the drains. Furthermore, where waste water is fed to a septic tank or other domestic sewage treatment system, it is likewise desirable that grease should be collected from the waste water prior to the waste water entering the septic tank, since the presence of grease in a septic tank may cause undesirable side effects, including reducing the natural biodegrading process which takes place in a septic tank.

Typically, known grease traps comprise a settling chamber within which waste water is allowed to settle prior to being discharged. Grease floats to the surface of the water in the settling chamber and solidifies. Typically, the solidified grease is subsequently removed through an inspection opening in the grease trap. Such grease traps suffer from a number of disadvantages. Firstly, in many instances it is difficult to remove the solidified grease from the settling chamber, secondly, if the waste water also includes entrained solids, the solids tend to collect in the bottom of the settling chamber, and these likewise can be difficult to remove. Furthermore, in many cases, if the volume of grease entrained in the waste water is excessive some of the grease may remain entrained in the water discharged from the grease trap.

There is therefore a need for a grease trap which overcomes these problems.

The present invention is directed towards providing such a grease trap.

According to the invention there is provided a grease trap for a waste water system, the grease trap comprising a housing defining a hollow interior region having an upstream end and a downstream end, an upstream inlet port being provided to the hollow interior region for receiving waste water into the hollow interior region at the upstream end thereof, a downstream outlet port being provided from the hollow interior region from which waste water is discharged from the hollow interior region at the downstream end thereof, an upstream partition and a downstream partition located in the hollow interior region and extending transversely thereof, the upstream and downstream partitions being spaced apart from each other and forming in the hollow interior region an upstream chamber for receiving waste water from the inlet

port, a downstream chamber from which waste water is discharged through the outlet port and an intermediate riser chamber intermediate the upstream and the downstream partitions, the downstream partition terminating in an upper edge defining an interior weir over which waste water flows from the riser chamber into the downstream chamber, a communicating opening extending through the upstream partition for communicating the upstream chamber and the riser chamber at a level below the interior weir, an outlet weir downstream of the downstream chamber for retaining waste water in the downstream chamber to the level of the outlet weir, and an upstream support means for supporting a removable upstream sludge collecting means in the upstream chamber for collecting entrained solids from waste water passing through the upstream chamber.

In one embodiment of the invention the outlet weir is set at a level lower than the interior weir. Preferably, the outlet weir is set at a level just slightly below the level of the interior weir.

In another embodiment of the invention an outlet opening is provided from the downstream chamber at a level lower than the outlet weir for communicating the outlet weir with the downstream chamber. Preferably, the outlet opening is located towards a lower end of the downstream chamber. Advantageously, an outlet riser extends between the outlet opening from the downstream chamber and the outlet weir for communicating the outlet weir with the downstream chamber. Ideally, the outlet port defines the outlet weir.

In one embodiment of the invention the communicating opening through the

upstream partition extends through the upstream partition at a lower end thereof.

In another embodiment of the invention a communicating means is provided between the outlet port and the hollow interior region for venting the outlet port to the hollow interior region.

Preferably, a downstream support means is provided in the downstream chamber for supporting a removable downstream sludge collecting means in the downstream chamber for collecting entrained solids from the waste water passing through the downstream chamber.

Advantageously, at least one inspection opening is provided to the hollow interior region. Ideally, a pair of spaced apart inspection openings are provided to the hollow interior region, one inspection opening being provided to the upstream chamber, and the other inspection opening being provided to the downstream chamber.

Advantageously, the riser chamber is accessible through at least one of the inspection openings. Preferably, each inspection opening is located for facilitating removal of the corresponding one of the upstream and downstream sludge collecting means.

In one embodiment of the invention a return rim extends around and outwardly of each inspection opening for receiving a closure cover. Preferably, each return rim defines an undercut for accommodating back fill or concrete for supporting the return rim.

In one embodiment of the invention the housing comprises a base, a pair of upstanding spaced apart side walls joined by spaced apart upstream and downstream end walls extending upwardly from the base, and a top wall spaced apart from the base and extending between the side walls and the upstream and downstream end walls, the base, side and end walls and the top wall defining the hollow interior region. Preferably, each inspection opening is provided in the top wall.

In one embodiment of the invention the upstream and downstream partitions are formed by inwardly extending return walls from the respective opposite side walls, which act to strengthen the side walls.

In another embodiment of the invention each support means in the upstream and downstream chambers are formed by side benching extending inwardly into the respective upstream and downstream chambers from the respective opposite side walls of the housing. Preferably, the side benching is formed by a return wall which acts to strengthen the corresponding side wall of the housing.

In one embodiment of the invention the housing is of plastics material.

In another embodiment of the invention the housing is formed by a rotational moulding process.

In a further embodiment of the invention the housing is formed by a rotational moulding process in one piece.

In one embodiment of the invention each sludge collecting means comprises an open mouth sludge collecting container for receiving waste water through the open mouth, and having at least one perforation in a side wall thereof for accommodating waste water therefrom. Preferably, the perforations of each sludge collecting means are formed by a plurality of spaced apart openings on respective opposite side walls of the sludge collecting container. Advantageously, the respective perforations are located in the respective side walls spaced apart above a base of each sludge collecting container. Ideally, the perforations in each side wall are located closer to the open mouth than to the base of each sludge collecting container.

Preferably, each sludge collecting container is shaped so that waste water passing through the one of the upstream and downstream chambers in which the sludge collecting container is located passes through the corresponding sludge collecting container. Advantageously, a spacing means is provided extending from each sludge collecting container for spacing each side wall of each sludge collecting container having the perforations therein spaced apart from an adjacent wall defining the one of the upstream and downstream chambers in which the sludge collecting container is located for accommodating waste water from the sludge collecting container through the perforations to the corresponding one of the upstream and downstream chambers.

The invention will be more clearly understood from the following description of a preferred embodiment thereof which is given by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of a grease trap according to the invention, Fig. 2 is a side elevational view of the grease trap of Fig. 1, Fig. 3 is an end view of the grease trap of Fig. 1 in the direction of the arrow Z of Fig. 2, Fig. 4 is a top plan view of the grease trap of Fig. 1, Fig. 5 is another perspective view of the grease trap of Fig. 1, Fig. 6 is another perspective view of the grease trap of Fig. 1, Fig. 7 is a further perspective view of the grease trap of Fig. 1, Fig. 8 is an exploded perspective view of the grease trap of Fig. 1, Fig. 9 is a partly exploded cross-sectional side elevational view of the grease trap of Fig. 1, Fig. 10 is a cross-sectional side elevational view of the grease trap of Fig. 1, Fig. 11 is a cut-away perspective view of the grease trap of Fig. 1,

Fig. 12 is a perspective view of a detail of the grease trap of Fig. 1, Fig. 13 is a side elevational view of the detail of Fig. 12, Fig. 14 is an end elevational view of the detail of Fig. 12, Fig. 15 is a top plan view of the detail of Fig. 12, and Fig. 16 is a cross-sectional perspective view of a portion of the grease trap of Fig. 1, in use.

Referring to the drawings there is illustrated a grease trap according to the invention indicated generally by the reference numeral 1 for use in a waste water system of a hotel, restaurant or industrial or domestic premises, for collecting grease and solids entrained in the waste water. The grease trap 1 comprises a housing 2 of plastics material formed in one piece by a rotational moulding process. The housing 2 comprises a base 3 a pair of side walls 4 extending upwardly from the base joined by upstream and downstream end walls 5 and 6, respectively, which extend upwardly from the base 3. A top wall 7 extends between the side walls 4 and the end walls 5 and 6 and defines with the base 3, the side walls 4 and the end walls 5 and 6 a hollow interior region 10. An inlet port 11 in the upstream end wall 5 delivers waste water into the hollow interior region 10, while waste water is discharged from the hollow interior region 10 through an outlet port 12 located at the downstream end wall 6. The inlet and outlet ports 11 and 12 are shaped and sized to receive a standard pipe fitting connector, such as, for example, a sleeve connector 13,

illustrated in some of the Figs. , of a plastics pipe waste water system.

An upstream partition 14 and a downstream partition 15 are located within the hollow interior region 10 and extend upwardly from the base 3 between the side walls 4 and form in the hollow interior region 10 an upstream chamber 17, a downstream chamber 18, and a riser chamber 19 between the upstream chamber 17 and the downstream chamber 18. The upstream chamber 17 receives waste water from the inlet port 11, and a communicating opening 20 extending through the upstream partition 14 adjacent the base 3 communicates the riser chamber 19 with the upstream chamber 17 for receiving waste water therefrom. The downstream partition 15 terminates in an upper edge, namely, an upper surface 22 which forms an interior weir 23 over which waste water flows from the riser chamber 19 into the downstream chamber 18. The upstream partition 14 defines an upper surface 25 which is at a level above the interior weir 23, and prevents flow of waste water between the upstream chamber 17 and the riser chamber 19. Thus, waste water is delivered from the upstream chamber 17 to the riser chamber 19 through the communicating opening 20.

An outlet opening 28 is formed in the downstream end wall 6 towards the base 3, and communicates the downstream chamber 18 with an outlet riser 29 which in turn communicates with the outlet port 12. The outlet port 12 is at a level above the outlet opening 28 and defines an outlet weir 30 for retaining waste water in the downstream chamber 18. The level of the outlet weir 30 defined by the outlet port 12 is at a level below the level of the interior weir 23 so that the waste water cascades over the interior weir 23 into the downstream chamber 18, and in turn

through the outlet weir 30.

Upstream and downstream sludge collecting means provided by a removable upstream sludge collecting container 33 and a removable downstream sludge collecting container 34 are located in the upstream and downstream chambers 17 and 18, respectively, for collecting entrained solids in the waste water. Respective support means provided by side benching 35 extending inwardly into the respective upstream and downstream chambers 17 and 18 from the respective opposite side walls 4 supports the sludge containers 33 and 34 in the respective upstream and downstream chambers 17 and 18.

An upstream inspection opening 37 and a downstream inspection opening 38 are provided in the top wall 7 for providing access to the hollow interior region 10. The upstream inspection opening 37 is located substantially above the upstream chamber 17 for facilitating removal and replacement of the upstream sludge container 33, while the downstream inspection opening 38 is located substantially above the downstream chamber 18 for likewise facilitating removal and replacement of the downstream sludge container 34. Access is provided to the riser chamber 19 for cleaning thereof through the downstream inspection opening 38 over the interior weir 23. Return rims 40 extend outwardly around each inspection opening 37 and 38 for receiving a closure cover 41 or an extension riser 42. Additionally, the return rims 40 are shaped to effectively form an undercut 43 which extends around the respective inspection openings 37 and 38 for accommodating back filling or concrete for supporting the return rim 40, and in turn, the closure cover 41 or an extension riser 42.

The upper surface 25 defined by the upstream partition 14 stops short of the top wall 7 so that the air space in the hollow interior region 10 above the water levels in the three chambers 17,18 and 19 intercommunicate. A communicating means, namely a communicating vent 45 communicates the outlet riser 29 and the outlet port 11 with the air space in the hollow interior region 10 for venting the outlet port 12 into the hollow interior region.

Turning now to the actual construction of the housing 2, the respective upstream and downstream partitions 14 and 15 are formed by respective half portions 46 which extend inwardly from the corresponding side walls 4 towards the centre 47 of the hollow interior region 10. Each half portion 46 of the respective upstream and downstream partitions 14 and 15 are formed by respective return walls, comprising spaced apart upstream and downstream secondary walls 50 and 51, respectively, which are joined by respective top secondary walls 52 all of which extend inwardly from the corresponding side walls 4. The top secondary wall 52 of the upstream partition 14 defines the upper surface 25, while the top secondary wall 52 of the downstream partition 15 defines the interior weir 23. A portion 57 of the downstream secondary wall 51 of the upstream partition 14 converges from a position at 58 towards the upstream secondary wall 50 and joins the upstream secondary wall 50 at the centre 47 of the hollow interior region 10. A portion 59 of the upstream secondary wall 50 of the upstream partition 14 also converges towards the portion 57 of the downstream secondary wall 51 so that the respective half portions 46 of the upstream partition 14 extending inwardly from the opposite side walls 4 define an upwardly extending groove 64 adjacent the centre 47 of the upstream partition 14.

The construction of the downstream partition 15 is similar to that of the upstream partition 14, with the exception that it is the upstream secondary wall 50 from which the portion 57 converges at 58 to the converging portion 59 of the downstream secondary wall 51 of the downstream partition 15. The converging portions 59 of the downstream secondary walls 51 of the downstream partition 15 define an upwardly extending groove 64 similar to that formed in the upstream partition wall 14.

The respective half portions 46 of the respective upstream and downstream partitions 14 and 15 are joined along a vertical seam during the rotational moulding process for preventing the flow of waste water therethrough. However, in the case of the upstream partition 14, intermediate side walls 60 extending upwardly from the base 3 join the upstream and downstream secondary walls 50 and 51, as does a bridge wall 61 so that the intermediate walls 60 and the bridge wall 61 form the communicating opening 20 through the upstream partition 14.

The upstream and downstream secondary walls 50 and 51 define external recesses 63 for receiving back filling when a cutting in the ground in which the grease trap 1 is located is being back filled for keying the grease trap 1 therein. The respective upstream and downstream secondary walls 50 and 51 and the top secondary walls 52 act to provide the side walls 4 with rigidity, and in turn the grease trap 1.

The side benchings 35 are formed by respective return walls comprising top support walls 65 and corresponding lower walls 66 which extend inwardly from the opposite side walls 4. The top support wall 65 of each side benching 35 forms a support for

the corresponding sludge container 33 or 34, and the lower wall 66 of each side benching 35 extends in a generally upwardly inwardly direction to converge to the top wall 65 at 67. The top support walls 65 and the corresponding lower walls 66 form external recesses 68 for receiving back filling when a cutting in the ground in which the grease trap is located is being back filled for keying the grease trap therein. The respective top support walls 65 and the corresponding lower walls 66 also provide rigidity to the side walls 4, and in turn to the grease trap 1.

Turning now to the sludge containers 33 and 34, the two containers 33 and 34 are of sheet metal material and are identical. The sheet metal may be sheet stainless steel or galvanised sheet steel. Each sludge container 33 and 34 comprises a base 70 upstanding side walls 71 which are joined by upstanding end walls 72. The base 70 and side and end walls 71 and 72 define a secondary hollow interior region 74 for collecting entrained solids in the waste water. The side and end walls 71 and 72 of each sludge container 33 and 34 define an open mouth 75 for accommodating waste water into the secondary hollow interior region 74. Five perforation openings 76 are provided in each side wall 71 for accommodating waste water from the secondary hollow interior region 74 into the corresponding upstream or downstream chamber 17 or 18. An outwardly extending rim 78 extends outwardly and around each sludge container 33 and 34 from the side and end walls 71 and 72 adjacent the open mouth. The rim 78 terminates in an upwardly extending lip 79 which co-operates with the adjacent end wall 5 or 6, and the adjacent upstream or downstream partition 14 or 15, as the case may be, for receiving and directing waste water into the secondary hollow interior region 74. In the case of the upstream sludge container 33 waste water is delivered into the secondary hollow interior region 74 from the inlet

port 11, and in the case of the downstream sludge container 34 waste water is delivered into the secondary hollow interior region 74 from the interior weir 23.

A portion 80 of the rim 78 extending from one of the side walls 71 extends for a distance greater than the rest of the rim 78 for engaging in both the case of the upstream and downstream sludge containers 33 and 34 the corresponding upstream or downstream partition 14 or 15. This facilitates removal and replacement of the respective upstream and downstream sludge containers 33 and 34 through the corresponding upstream and downstream inspection openings 37 and 38. A handle 82 extends between the lips 79 adjacent the end walls 72 of each sludge container 33 and 34. By gripping the handle 82 and raising the respective sludge containers 33 and 34 until the wide rim portions 80 clear the top secondary walls 52 of the respective upstream and downstream partitions 14 and 15, the sludge containers 33 and 34 can then be urged in the direction of the arrows Y, see Fig. 9, for alignment with the corresponding upstream and downstream inspection openings 37 and 38.

Additionally, the provision of the rim 78 extending from the side walls 71 spaces the corresponding side walls 71 from the adjacent upstream or downstream end wall 5 or 6 and the adjacent upstream or downstream partition 14 or 15 for accommodating flow of waste water through the perforation openings 76 from the secondary hollow interior regions 74 of the respective sludge containers 33 and 34 into the corresponding upstream and downstream chambers 17 and 18.

Projections 81 extend outwardly from the wide rim portions 80 of the respective sludge containers 33 and 34 for engaging the corresponding upwardly extending

grooves 64 in the corresponding upstream and downstream partition 14 and 15 for facilitating locating the sludge containers 33 and 34 in the respective upstream and downstream chambers 17 and 18, respectively, and for preventing insertion of the sludge containers 33 and 34 when the sludge containers 33 and 34 are incorrectly orientated relative to the respective upstream and downstream chambers 17 and 18, respectively.

In use, the grease trap 1 is lowered into a cutting in the ground, and the inlet and outlet ports 11 and 12 are connected to the waste water system. If required the extension risers 42 are placed on the return rims 40 of the respective upstream and downstream inspection openings 37 and 38. The grease trap 1 is then back filled, and the back filling extends into recesses 63 and 68 formed by the respective half portions 46 of the upstream and downstream partitions 14 and 15 and by the side benchings 35, respectively. Additionally, back filling, and if desired concrete extends into the undercuts 43 extending around and beneath the return rims 40 for strengthening the return rims 40 and for supporting the load of the extension risers 42 and/or the closure covers 41.

Waste water enters the hollow interior region 10 through the inlet port 11 and flows through the upstream chamber 17, the riser chamber 19, the downstream chamber 18, and in turn through the outlet opening 28, the outlet riser 29 and over the outlet weir 30 through the outlet port 12 in the direction of the arrows A. Accordingly, waste water with solids and grease entrained therein is initially passed into the secondary hollow interior region 74 of the upstream sludge container 33 which collects entrained solids in the waste water. The upstream chamber 17 acts as a

settling chamber and entrained grease in the waste water rises to the surface of the waste water where it cools and solidifies and collects. The upstream partition 14 retains the collected solidified grease in the upstream chamber 17. The waste water then flows from the upstream chamber 17 through the communicating opening 20 into the riser chamber 19 within which the waste water rises, and flows over the interior weir 23 into the downstream chamber 18. The downstream chamber 18 also acts as a settling chamber, and any remaining grease entrained in the waste water rises to the surface and solidifies and collects on the surface of the water in the downstream chamber 18. Any remaining entrained solids in the waste water settle and are collected in the secondary hollow interior region 74 of the downstream sludge container 34. Waste water which in general is completely free of entrained solids and grease then passes from the downstream chamber 18 through the outlet opening 28 and rises through the outlet riser 29 and is discharged through the outlet port 12.

Periodically collected grease and solids are removed from the grease trap 1 by removing the sludge collecting containers 33 and 34 from the upstream and downstream chambers 17 and 18, respectively. The covers 41 are removed from the inspection openings 37 and 38 and the respective sludge collecting containers 33 and 34 are gripped by their respective handles 82 and raised upwardly in the direction of the arrows X, until the wide rim portions 80 clear the corresponding top secondary wall 52 of the adjacent one of the upstream and downstream partitions 14 and 15. Once the wide rim portions 80 clear the adjacent top secondary walls 52 the sludge collection containers 33 and 34 are then urged in the directions of the arrows Y for aligning the respective sludge collecting containers 33 and 34 with the

corresponding inspection openings 37 and 38, respectively. The sludge collecting containers 33 and 34 are then raised upwardly through the inspection openings 37 and 38 and removed therethrough. As the sludge collecting containers 33 and 34 are being raised upwardly in the direction of the arrows X, solidified grease on the surface of the water in the respective upstream and downstream chambers 15 and 18 is collected by the sludge collecting containers 33 and 34, and is thus removed from the grease trap 1 as the sludge collecting chambers 33 and 34 are removed therefrom. The collected sludge and grease in the sludge collecting containers 33 and 34 is removed therefrom, and the sludge collecting containers are cleaned and returned to the respective upstream and downstream chambers 17 and 18.

The advantages of the invention are many. Firstly, by virtue of the fact that the hollow interior region is formed into three chambers, two of which, namely, the upstream and downstream chambers are settling chambers virtually all entrained solids and grease in the waste water are collected in the grease trap 1. A further important advantage of the invention is achieved by the construction of the housing.

The construction of the housing provides a relatively strong rigid and self supporting grease trap which is ideally suited for manufacture by rotational moulding. The upstream and downstream partitions impart significant rigidity and strength to the housing, as do the side benchings. Furthermore, the fact that the upstream and downstream partitions are formed in half portions which extend inwardly from the side walls, and converge so that the respective upstream and downstream secondary walls of the respective partitions join along a vertical seam add significant strength to the housing. By virtue of the fact that the housing is constructed to have such strength, there is no danger of the housing collapsing when backfilled.

Additionally, the grease trap is ideally suited to rotational moulding.

Claims

Claims 1. A grease trap for a waste water system, the grease trap comprising a housing defining a hollow interior region having an upstream end and a downstream end, an upstream inlet port being provided to the hollow interior region for receiving waste water into the hollow interior region at the upstream end thereof, a downstream outlet port being provided from the hollow interior region from which waste water is discharged from the hollow interior region at the downstream end thereof, an upstream partition and a downstream partition located in the hollow interior region and extending transversely thereof, the upstream and downstream partitions being spaced apart from each other and forming in the hollow interior region an upstream chamber for receiving waste water from the inlet port, a downstream chamber from which waste water is discharged through the outlet port and an intermediate riser chamber intermediate the upstream and the downstream partitions, the downstream partition terminating in an upper edge defining an interior weir over which waste water flows from the riser chamber into the downstream chamber, a communicating opening extending through the upstream partition for communicating the upstream chamber and the riser chamber at a level below the interior weir, an outlet weir downstream of the downstream chamber for retaining waste water in the downstream chamber to the level of the outlet weir, and an upstream support means for supporting a removable upstream sludge collecting means in the upstream chamber for collecting entrained solids from waste water passing through the upstream chamber.
2. A grease trap as claimed in Claim 1 in which the outlet weir is set at a level lower than the interior weir.

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3. A grease trap as claimed in Claim 1 or 2 in which the outlet weir is set at a level just slightly below the level of the interior weir.
4. A grease trap as claimed in any preceding claim in which an outlet opening is provided from the downstream chamber at a level lower than the outlet weir for communicating the outlet weir with the downstream chamber.
5. A grease trap as claimed in Claim 4 in which the outlet opening is located towards a lower end of the downstream chamber.
6. A grease trap as claimed in Claim 4 or 5 in which an outlet riser extends between the outlet opening from the downstream chamber and the outlet weir for communicating the outlet weir with the downstream chamber.
7. A grease trap as claimed in any preceding claim in which the outlet port defines the outlet weir.
8. A grease trap as claimed in any preceding claim in which the communicating opening through the upstream partition extends through the upstream partition at a lower end thereof.
9. A grease trap as claimed in any preceding claim in which a communicating means is provided between the outlet port and the hollow interior region for venting the outlet port to the hollow interior region.
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to A grease trap as claimed in any preceding claim in which a downstream support means is provided in the downstream chamber for supporting a removable downstream sludge collecting means in the downstream chamber for collecting entrained solids from the waste water passing through the downstream chamber.
11. A grease trap as claimed in any preceding claim in which at least one inspection opening is provided to the hollow interior region.
12. A grease trap as claimed in Claim 11 in which a pair of spaced apart inspection openings are provided to the hollow interior region, one inspection opening being provided to the upstream chamber, and the other inspection opening being provided to the downstream chamber.
13. A grease trap as claimed in Claim 11 or 12 in which the riser chamber is accessible through at least one of the inspection openings.
14. A grease trap as claimed in any of Claims 11 to 13 in which each inspection opening is located for facilitating removal of the corresponding one of the upstream and downstream sludge collecting means.
15. A grease trap as claimed in any of Claims 11 to 14 in which a return rim extends around and outwardly of each inspection opening for receiving a closure cover.

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16. A grease trap as claimed in Claim 15 in which each return rim defines an undercut for accommodating back fill or concrete for supporting the return rim.
17. A grease trap as claimed in any of Claims 11 to 16 in which the housing comprises a base, a pair of upstanding spaced apart side walls joined by spaced apart upstream and downstream end walls extending upwardly from the base, and a top wall spaced apart from the base and extending between the side walls and the upstream and downstream end walls, the base, side and end walls and the top wall defining the hollow interior region.
18. A grease trap as claimed in Claim 17 in which each inspection opening is provided in the top wall.
19. A grease trap as claimed in Claim 17 or 18 in which the upstream and downstream partitions are formed by inwardly extending return walls from the respective opposite side walls, which act to strengthen the side walls.
20. A grease trap as claimed in any of Claims 11 to 19 in which each support means in the upstream and downstream chambers are formed by side benching extending inwardly into the respective upstream and downstream chambers from the respective opposite side walls of the housing.
21. A grease trap as claimed in Claim 20 in which the side benching is formed by a return wall which acts to strengthen the corresponding side wall of the housing.

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22. A grease trap as claimed in any preceding claim in which the housing is of plastics material.
23. A grease trap as claimed in Claim 22 in which the housing is formed by a rotational moulding process.
24. A grease trap as claimed in Claim 23 in which the housing is formed by a rotational moulding process in one piece.
25. A grease trap as claimed in any preceding claim in which each sludge collecting means comprises an open mouth sludge collecting container for receiving waste water through the open mouth, and having at least one perforation in a side wall thereof for accommodating waste water therefrom.
26. A grease trap as claimed in Claim 25 in which the perforations of each sludge collecting means are formed by a plurality of spaced apart openings on respective opposite side walls of the sludge collecting container.
27. A grease trap as claimed in Claim 25 or 26 in which the respective perforations are located in the respective side walls spaced apart above a base of each sludge collecting container.
28. A grease trap as claimed in Claim 27 in which the perforations in each side wall are located closer to the open mouth than to the base of each sludge collecting container.

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29. A grease trap as claimed in any of Claims 25 to 28 in which each sludge collecting container is shaped so that waste water passing through the one of the upstream and downstream chambers in which the sludge collecting container is located passes through the corresponding sludge collecting container.
30 A grease trap as claimed in any of Claims 25 to 29 in which a spacing means is provided extending from each sludge collecting container for spacing each side wall of each sludge collecting container having the perforations therein spaced apart from an adjacent wall defining the one of the upstream and downstream chambers in which the sludge collecting container is located for accommodating waste water from the sludge collecting container through the perforations to the corresponding one of the upstream and downstream chambers.
31. A grease trap substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.