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Get Up to Speed on Grease Traps: How They Work, How They’re Cleaned, and How Bacteria Fit In

Apr 19, 2021

How Grease Traps Work

A grease trap is a plumbing device designed to intercept most greases and solids before they enter wastewater disposal system, and they are required in most restaurants and food establishments throughout the U.S. The traps reduce the amount of fat, oil, and grease (FOG) that enter buildings’ plumbing, waste collection systems, and municipal wastewater treatment plants, helping prevent:

  • Structure fires (grease traps are the biggest culprit)
  • Decreased system capacity (as grease sticks to the insides of pipes)
  • Frequent cleaning and replacement of pipes and other vessels
  • Raw sewage backups and overflows, which pollute the environment and increase human contact with pathogens
  • Higher costs of operation and maintenance
  • Less effective treatment, which can affect the quality of local water sources

While specific regulations vary by municipality, there is generally a maximum FOG discharge concentration of around 100 milligrams per liter per establishment, and grease must be captured from fixtures like:

  • Pot sinks
  • Rinse sinks at dishwashers
  • Dishwashers
  • Woks
  • Floor drains and sinks
  • Automatic hood washers

This can be accomplished using 2 different types of grease traps: larger traps outside a building (usually in the ground) to serve an entire kitchen or smaller, point-of-use traps placed on or near the kitchen fixture it serves.

In either case, the grease trap tank acts as a reservoir, holding the wastewater, FOG, and food solids that enter. As cooling occurs, the food solids settle, and the FOG (being lighter than water) float to the top. The water is flushed out, and the grease and solids remain in the trap.

How Grease Traps Are Cleaned

To maintain proper operation, grease traps need to be opened and the grease and solids removed on a regular basis. The grease trap manufacturer should be consulted for specific instructions, but general cleaning guidelines are as follows.

  • Grease traps should be cleaned when 25% of the liquid level is FOG, which is generally:
    • Quarterly for whole-kitchen traps
    • Once a month for point-of-use traps
  • Carefully remove covers to avoid gasket damage
  • Skim off floating FOG with a tool such as a ladle
  • Remove baffles and scrape them clean
    • Baffles should only be rinsed in sinks that flow into a trap
  • Scrape the bottom of the trap to remove settled food solids with a tool such as a strainer
  • Clean the bypass vent using a flexible wire
  • Reinstall baffles and cover

Most establishments hire an independent contractor to clean whole-kitchen grease traps, but leave point-of-use traps to employees. No matter who cleans a grease trap, bleach, ammonia, or any other unapproved chemicals should NEVER be added. In fact, some municipalities only allow a single additive: bacteria

How Bacteria Fit In

Bacteria excrete enzymes, which break down organic waste, like FOG, into smaller particles, which the bacteria then consume.

The byproducts of digestion are more bacteria, water, and carbon dioxide, which are natural and harmless. The bacteria continue to work (reproducing and consuming organic material) long after application and until their food source is eliminated, providing a continuous and effective method of cleaning grease traps.

Green Earth® DT 7 from Betco® is a unique, NSF-certified liquid bacterial blend formulated specifically to control FOG levels and odors associated with grease traps and drain systems. The concentrated microbial blend aggressively targets proteins, lipids, and carbohydrates and is perfect for:

  • Lowering FOG levels that are in exceedance of discharge limits
  • Significantly reducing grease trap pump out frequency and cost
  • Lowering grease disposal costs
  • Preventing blockages
  • Eliminating malodors at the source

By implementing consistent grease trap cleaning practices, including regular addition of bacteria through use of DT 7, restaurants and food service establishments can significantly reduce FOG-related headaches, including fines, legal issues, fires, plumbing blockages, overflows, and more.