Grease Traps

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Grease Traps in Washington, DC

A grease trap (also called a grease interceptor) is a receptacle installed between your building’s sewer line and the city’s sewer main. As wastewater flows into the grease trap, fats, oils, and grease (FOG) floats to the top of the chamber. Solids will sink to the bottom of the chamber, leaving only liquid waste water to flow into the sewer main.

A grease trap is necessary for preventing damage to the city’s sewer main. FOG deposits clog sewer mains so thoroughly that many cities have made grease interceptor installation mandatory. Not only does a grease trap protect your plumbing and business operations, but it could also save you from a hefty municipal fine.

We install and service grease traps for various food service establishments (FSE):

  • Restaurants
  • Hotel kitchens
  • Hospitals
  • School kitchens
  • Bars
  • Factory cafeterias
  • Clubs

Since 1950, we have been taking care of our local community’s grease interceptor installation and pumping needs. We know that on every job we do, our reputation is at stake. That’s what it takes to deliver exceptional quality. Call now to request an estimate or schedule service.

grease interceptors

What Kinds of Grease Does It Handle?

Not all grease is the same. A grease trap handles both yellow and brown grease:

  • Yellow grease – Also known as fryer oil and/or cooking oil, this type of grease consists of used cooking oil, used and/or recycled vegetable oil, and waste vegetable oil. It is yellow in nature, hence its name. This type of grease is used in secondary products such as soap, detergents, and animal feed, as well as for biodiesel vehicles.
  • Brown grease – This type of grease refers to fats, oils, and grease that do not fit into the categories of yellow grease. Brown grease has a high level of fatty acids, so it can’t be used for animal feed. This type of grease can also come from sources like commercial dishwashers and kitchen floors drains, so it can be very dirty and quite odiferous.

Volume–Based Grease Traps (300 Gallons and Above)

A volume–based grease trap works based on volume and the retention time of the wastewater. The average size is 300 gallons, and this type of trap is most typically installed underground or outside. This type of grease  interceptor does not need an upstream sink tail piece flow restriction or flow control device. According to Chapter 21–1502, all volume–based grease traps that reside outside must be cleaned and pumped every 90 days; this is the same for the WSSC (Washington Suburban Sanitary Commission), 818.4.3.

Flow–Based Grease Interceptors/Traps (Under 300 Gallons)

A flow–based grease trap is going to be sized and operated in accordance with the flow rate of the wastewater coming into the trap. This type of grease trap has a specific requirement for an upstream sink tail piece flow restriction and a flow control device. There are two kinds of flow–based grease interceptors: passive flow–based interceptor and a mechanical flow–based interceptor. A passive flow–based interceptor has no mechanical grease removal features while a mechanical one does.

All indoor grease abatement systems must be pumped and cleaned every 30 days according to Chapter 21–1502 codes of Washington, DC. Additionally, according to the WSSC, 818.4.3, the maintenance and cleaning for all flow–based grease interceptors must be performed by the standards set forth by the manufacturer or by the 25% rule, whichever is the more stringent.

Pump Trucks

Our pump trucks, also known as vacuum trucks, are used to pump or evacuate the contents from grease traps, grease interceptors, oil/sand interceptors, and other types of liquid waste. Once the systems are evacuated we dispose of the materials at approved facilities.

Grease Recovery Unit

A grease recovery unit (GRU) is a special type of grease trap that uses internal mechanical parts and heat via an electrical connection to automatically skim the grease off the top and feed it into a barrel. The mechanical components must be regularly checked and serviced for proper operations. The barrels of the grease recovery units must be pumped as well. With 70 years of experience, you can count on Magnolia to service your grease recovery unit and ensure that it is functional and hygienic.

pump truck

Most local codes require volume-based grease traps to be pumped on a quarterly basis or by the 25% rule, whichever is more stringent. The wastewater in every grease interceptor is separated into (3) three distinct layers. All heavy solids will fall to the bottom and this layer is referred to as sludge while all lighter material such as grease will float to the top and this is referred to as the scum layer. The rest of the wastewater will remain in the middle and this layer is referred to as the clear zone.

When the layer of scum and sludge added together surpass 25% of the total liquid depth, it is time to have the grease interceptor pumped. This can only be determined when a competent contractor uses a sludge judge, dipstick, or similar tool to take these measurements. Most flow-based grease traps require daily maintenance and should be fully pumped at least monthly, however, local codes differ in requirements.

Unless the tank is being pumped by a contractor it should always be holding wastewater. The liquid level should be at the invert (bottom) of the outlet line. If the liquid level is below this point, there is a chance that the tank itself has been compromised and is actually leaking. This should be inspected by a qualified contractor. If the liquid level is above the invert of the outlet line, it is an indication of a problem with a downstream component.

Absolutely! Dishonest contractors are notorious for “skimming,” or only removing the scum layer from an interceptor. They do this so they can complete more jobs before being required to go to a disposal facility. A proper pumping of a grease trap/interceptor includes evacuating all contents from the tank.

Local codes will determine requirements. Some require volume-based interceptors to be powerwashed annually. However, the requirements are vague at best. When a pumping contractor pumps a volume-based grease trap they will only be able to evacuate the loose contents if they do not introduce a power-washing process. Grease, over time, will harden and stick to the surfaces of the grease interceptor.

The only way to remove this grease is to introduce additional cleaning methods, such as scraping the walls and powerwashing with a high-pressure water jet. We feel that a volume-based grease trap should be completely powerwashed at least annually and this should include a thorough water-jetting of the inlet and outlet drain lines to ensure that they are clean and free of anything that will result in a sewer stoppage.

Magnolia Plumbing, Heating & Cooling provides Commercial Liquid Waste Pumping services in the DMV area, including Washington DC, Silver Spring, Alexandria, and Arlington. View our service area here.