Commercial Kitchen Grease Traps
Restaurants and other commercial kitchens are required to have grease traps or grease interceptors. These devices help ensure that the water supply for the community stays free of grease and oil. The size of your kitchen and the volume of wastewater that flows from the sink will determine the device you need.What is the difference between a trap and an interceptor?
Grease traps and grease interceptors are both installed in restaurant plumbing systems to collect grease and other solid waste. The goal is to keep this material out of the wastewater disposal system, but the difference between the two is a matter of their capacity and location. Commercial grease traps are smaller and are usually located under a sink. Commercial grease interceptors are large, underground tanks that are located outside the restaurant.What types of commercial grease traps are available?
There are two basic styles of grease traps. One works through the passive effect of gravity, and one employs baffles to increase efficiency.
- Passive: The passive style has an inflow pipe from the sink and an outflow to the sewer system. It essentially acts as a holding tank to give the waste material time to separate on its own. Fat, oil, and grease, referred to in the industry as “FOG,” is lighter than water and floats to the top. Food waste and other solids are heavier and form a sludge that sinks to the bottom. The wastewater flows between these two layers and exits into the sewer system.
- Hydromechanical: This style contains baffles to slow the flow of materials so they have more time to separate. The system first controls the amount of water that is allowed into the trap from the drain. It then mixes the water with air to improve the efficiency of the separation.
The main consideration is the device’s gallons-per-minute flow rating. Hydromechanical types usually top out at about 100 gallons per minute. Passive equipment can handle higher rates of flow.
There are three ways to determine the size of trap your kitchen needs:
- Size of inflow pipe: Some manufacturers will list an approximate flow rate for their devices based on the diameter of the plumbing fixtures.
- Drain Fixture Units: DFUs are defined by the Uniform Plumbing Code. You can add the DFUs for all the fixtures that are going to be draining into the trap and use this number to estimate the equipment you need.
- Measurement of actual fixtures: This is the most exact, but most complicated, method. It involves directly measuring the capacity and emptying rate of the fixtures in your kitchen to determine the gallons-per-minute flow rate.
All grease traps do require regular cleaning. Professionals or restaurant employees can perform the cleaning. The standard rule is that the trap should be cleaned when it is one-fourth full of grease. Most commercial establishments will reach this point every one to three months, depending on how busy the kitchen is.