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What is a Grease Trap?

Simply put, a grease trap is something kitchen wastewater flows through before entering the sewer waste system.

Large establishments like Restaurants Bars and Cafes need a grease interceptor (or "grease trap"), and it's one of the more important features of a commercial kitchen.

The FOG (fat, oil and grease) that these kitchens need to dispose of is far greater in volume and frequency, requiring a specialized device to ensure pipes and the things they connect to remain functional and safe.

A grease trap works by slowing down the flow of warm/hot greasy water and allowing it to cool. As the water cools, the grease and oil in the water separate out and float to the top of the trap. The cooler water - minus the grease - continues to flow down the pipe to the sewer.

Peer into a grease trap and you'll see a mat of grease. When this mat of grease gets deep enough(Approx 2 inch), the trap must be cleaned out.

There are two primary methods that grease traps/interceptors use to separate out the FOG, each of which is suited to certain applications.

Interceptors come in smaller versions designed for indoor connection to individual sinks and other fixtures (usually with a total flow less than 50-100 Gpm) and larger ones that are installed outdoors and underground, to service entire establishments.

Smaller Grease Traps

Called "hydromechanical grease interceptors", the smaller, indoor types utilize internal baffles to lengthen the path of flow, providing more time and space for separation. Vented flow control devices regulate the amount of wastewater entering the device, and mix air in with it to efficiently separate FOG from solids and water. The FOG that solidifies at the top of the tank, as well as the relatively heavy food solids that fall to the bottom, need to be cleaned out often by professionals.

Larger Grease Interceptors

The larger "passive" or "gravity" interceptors rely more on time and gravity to separate FOG, which is about 80% lighter than water. Larger tank sizes, internal baffling, and standpipes increase the "retention time" on these passive units, allowing gravity to work its magic. These interceptors are usually cleaned out on a routine basis by professionals.

Restaurant and foodservice kitchens produce much waste grease which is present in the drain lines from various sinks, dishwashers and cooking equipment such as combi ovens and commercial woks. If not removed, the grease can clump and cause blockage and back-up in the sewer.

Nearly all municipalities require commercial kitchen operations to use some type of interceptor device to collect grease before it enters sewers. Where FOG is a concern in the local wastewater system, communities have established inspection programs to ensure that these grease traps and/or interceptors are being routinely maintained.

When possible, interceptors should be cleaned out to ensure the best quality and performance.

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