A grease interceptor is a plumbing accessory people use to keep grease out of the sewer system. Normal household grease is not a significant concern, but in any setting where people work with lots of greases, fats, oils, and waxes, it is necessary to protect the sewer with a grease interceptor. Often the municipal code requires the use of such devices and people must make sure they are in good working order. In facilities like restaurants, a public health inspector can ask to verify that employees are cleaning it out regularly.
If grease escapes into the sewer, it can cause a number of problems. One is clogs. Many types of grease and wax can solidify at low temperatures and form plugs in the line, forcing workers to clear the plumbing line after it starts to clog. Grease can also disturb the balance of microorganisms in the sewage and may make it harder to treat, in addition to creating a substantial mess at sewage treatment plants.
The basic grease interceptor design consists of a large tank. Water from the drains flows into the tank and settles. Solids sink to the bottom, while lightweight grease floats to the top, leaving clear water in the middle. The water flows through to a second tank and discharges to the sewer system through a small pipe. Many also have baffles or screens to trap debris and large chunks of material as they flow into the primary tank.
Maintenance of a grease interceptor requires periodically pulling out and cleaning the screens as well as removing solids and greases. These materials can go into a drum for disposal. Rendering plants may have use for the grease, and it can also be used to make biofuels in some cases, depending on what kinds of grease are present. Restaurants with large amounts of cooking oil usually have a contract with a rendering company to pick up drums of grease on a regular basis.
People building a restaurant or other facility where grease will be present can check the building code for any specific requirements related to grease control. Plumbers familiar with the code in a region can recommend specific products to meet the need on the basis of the type of facility. Numerous manufacturers produce grease interceptors along with replacement baffles and other parts for maintenance and repairs. Some things people may want to think about include ease of cleaning and the handling capacity; it is a good idea to purchase a slightly larger grease interceptor than necessary, in case production increases.