Resource Centre | Grease Trap Resources

Flow Restrictors

A flow restrictor is a device that is designed to reduce the drainage flow rate so that smaller grease interceptors can be used. They do this by constricting the drainage pipe size between a plumbing fixture and the grease interceptor. We strongly discourage the use of grease interceptors that require a flow restrictor device. Although smaller interceptors cost less initially, the overall lifetime cost is substantially higher than adequately sized interceptors that do not require flow restrictors, and they present a much higher risk of drain problems and sewer-use bylaw infractions (see interceptor sizing).



Less flow = less retention time = smaller interceptor
Smaller interceptor = less efficiency = increased drainage and bylaw risk + increased maintenance costs


Flow restrictors are extremely susceptible to blockage and cause the fixtures they service to discharge very slowly (as much as 10 times slower) which can causes serious operational problems.

flow restrictors

Flow restrictors can be separate fixture units installed in the drainage system, or integral restrictor gates/plates installed directly on the inlet of small "box" type grease interceptors. Flow restrictors are required wherever small box type grease interceptors are used.

Flow restrictors should never be removed. Removing a flow restrictor will severely reduce the grease interceptor's efficiency, thus increasing the risk of drain blockages and sewer-use bylaw infractions.



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