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Grease Traps

Grease Traps

Grease disposal can be a hassle for many small business owners, but some states and municipalities require these units to help keep sewer systems clean and free of grease waste from restaurants. Cue: grease traps. These devices, optional for some and mandatory for others, are used to intercept most grease and solids in plumbing systems before it ever reaches your wastewater disposal unit and further sewer lines. Knowing the ins and outs of grease traps can help you make an informed decision on which trap is right for your restaurant and can help reduce your restaurant’s impact on the local wastewater systems!

Grease traps for restaurants are often used in conjunction with commercial dishwashers and dishwashing sinks. Also known as grease interceptors, grease recovery devices, and grease converters, these systems typically connect via a flow restrictor on the inlet side (to slow incoming water to allow it to redirect through the system). As water slows in the unit, grease and other solids accumulate at the top of the static water, effectively trapping greasy goo that is unfit for processing in wastewater!


Commercial grease traps are sized according to the rate of incoming flow in gallons per minute (GPM) and the trap's capacity, which is listed in pounds as twice the flow rate. So for example, a system with a 10 GPM trap can handle 20 pounds. While these calculations are generally accepted by most plumbers and municipalities, you’ll always want to check with local authorities to ensure your trap meets your area’s code.

For pot washing sinks, you’ll need to know the area of your sink in cubic inches (of all compartments combined), and convert this capacity to GPM by dividing by 231. Adjust for displacement by multiplying by .75 to get the resulting GPM. The resulting GPM is the required flow rate to drain the sink in one minute. You would then choose a grease trap with a GPM flow rate close to this number. If you plan to drain multiple sinks into one trap, add 100% of the largest rate, 50% of the second-largest, and 25% of the rest to get the recommended flow rate for your grease trap.

Dish machines require a little less math, as the Plumbing and Drainage Institute (PDI) has set up some recommendations:

  • 10-15 Gallon Capacity Dish Machine Tank: 15 Pound Grease Trap

  • 20-30 Gallon Capacity Dish Machine Tank: 20 Pound Grease Trap

  • 30-50 Gallon Capacity Dish Machine Tank: 25 Pound Grease Trap

  • 50-70 Gallon Capacity Dish Machine Tank: 35 Pound Grease Trap

  • 70-100 Gallon Capacity Dish Machine Tank: 100 Pound Grease Trap


There are three different types of traps: Passive, In-Ground, and Grease Recovery Devices (GRDs). Passive systems attach to plumbing under your sink but within your kitchen. These are by far the most common. In-Ground tanks are outside of your kitchen and, as the name implies, located underground. GRDs remove grease automatically, and the grease can be recycled with your waste fryer oil. This type of trap doesn’t cost the restaurant any additional money for grease disposal unlike passive and in-ground systems.


As with any commercial kitchen product, you’ll achieve the longest lifespan if you maintain the equipment regularly. Use a drain maintainer or cleaner on a regular basis to keep your grease trap working properly. Remove grease from the trap as indicated based on the type of trap, usage, and capacity.


Sales Consultant


E Friedman Associates Inc

T: 516-882-1955

D: 712-389-6805

F: 605-782-9015



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