A grease trap is designed to prevent greasy substances from entering plumbing systems, septic tanks, and waste water treatment facilities where they are difficult to process and may create a number of environmental problems. Understanding how to size a grease trap is an important way to keep your establishment up to code and ensure that your plumbing is running smoothly.
A restaurant grease trap is often specified for a pot washing stainless steel sink or a dish machine. A flow restrictor on the inlet side of the trap slows the incoming flow and redirects it through baffling inside the trap. This slowing and baffling process allows lighter-than-water substances like fats, oil, and grease to accumulate inside the trap above the static water line while the water flows out below. Essentially, a grease trap works by using gravity to separate heavier water from lighter fats.
Local plumbing codes typically determine design and installation criteria, but they typically follow the guidelines set forth by the Plumbing & Drainage Institute (PDI). If you're wondering how to install a grease trap, contact your local municipality to learn more about installation criteria for your area.
If you operate a restaurant or other commercial facility, you may have wondered "what size grease trap do I need?" Commercial grease traps are sized according to the rate of incoming flow, in gallons per minute (GPM). Associated with this incoming flow rate is the trap's capacity. This rated capacity, in pounds, is listed at twice the flow rate. For example, a 10 GPM trap has a rated capacity of 20 pounds.
*All calculations, formulas, and charts used to determine grease trap sizing and capacities are widely accepted by most plumbers and regulatory agencies. Always check with your local authority and plumber for specific regulations and recommendations on grease trap sizing.