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Posted on July 6, 2021

If you’ve never smelled the rotting food and grease that builds up in a grease trap, count yourself lucky. Many restaurant workers know the experience. Ideally, only people working in your restaurant and contractors who clean your grease trap or interceptor should know that smell, but a buildup of grease over time can cause your pipes to backup. If that happens, you’ll have some explaining to do to your unlucky customers.

Grease Trap Basics

Grease traps and interceptors use the physical properties of grease, water, and solids to separate the water from the rest of that gunk. Water with fat, oils, and grease (FOG) comes in through a pipe into one section. The water slows down as it enters the trap, and grease floats to the top while solids sink to the bottom. At the other end, clean water exits through an opening.

Grease traps are necessary because FOG doesn’t just go away, it clings to the sides of pipes and builds up over time. Traps exist to prevent FOG from entering the municipal water supply or the environment.

Grease Trap vs. Grease Interceptor

There are two main types of grease traps: a trap and an interceptor. The difference between a grease trap and a grease interceptor is more about volume than function. Both allow fats and solids to separate from water. However, grease traps are smaller and are designed to clean water with a flow rate of up to 50 gallons per minute. They can be installed just underneath commercial kitchen sinks or beneath the floor in an accessible space.

Grease interceptors handle water flow rates above and beyond 50 gallons per minute. They are made from concrete and can be up to the size of a small car. There are two main compartments in an interceptor, so a grease interceptor installed beneath the ground has two manhole covers for servicing.

Cafes, sandwich shops, and small restaurants can use grease traps, while large restaurants, schools, and malls will have grease interceptors to handle larger flows. Since grease traps are smaller, they fill up faster and need to be cleaned more frequently. Restaurant employees may empty the trap themselves each night if it’s easily serviceable, or a professional service may clean it once or twice a month.

Grease interceptors need to be cleaned less often because they have a larger capacity. However, cleaning a grease interceptor is a huge task, and it requires a sanitary contractor to pump out the grease and solids into a truck. This typically happens quarterly to monthly.

What Happens When Grease Traps Fill Up

A grease trap is designed to trap grease, of course. But when too much time has gone between cleanings, its efficiency is reduced. That can cause more grease to make it into the municipal water system or even cause clogs and backups in the business establishment.

If too much grease builds up on top of the water inside the trap, it takes up room for water to flow through the trap. This restricts efficiency. The exit pipe also has an outlet cap on the upper side, and if the cap is missing, grease can overflow into the clean water if it reaches a high level.

If too many solids build up in the bottom of the tank, this can restrict water flow as well. Dirty water will exit the tank and clogs will slow your drains, and that’s not good. Most cities require restaurants to clean their grease traps often enough to maintain FOG levels of 25% or less.

Consequences of Not Cleaning Your Grease Trap

From city fines to the stench of rotting food, there are a lot of consequences for not performing regular grease trap cleaning. Here are some examples.

  • Rotting smell: One of the first things you may notice is the smell of rotting food. Without routine grease trap pumping, the smell can make it unpleasant for employees to work and customers to dine in your establishment.
  • Backups: Clogged grease trap pipes can cause the drains connected to the trap to backup in your restaurant. This creates unsanitary food preparation conditions and expensive damage.
  • Corrosion: Beyond causing unpleasant odors, rotting food and water combine to make sulfuric acid. This corrodes the steel and concrete tanks and can cause leaks. You can’t just repair a grease trap that has been damaged, you need to replace it (and pay the unplanned cost).
  • Sewer overflow: A full grease trap can let grease escape into the city sewer and clog the lines. If that happens, other drains in the area could have backups and the city could slap on some hefty fines.
  • Extra cleaning costs: If you go too long without a grease trap cleaning, the service provider may charge more to tackle the job since it will take more time. That’s why it isn’t a good idea to try to save money by doing less frequent cleanings, because you won’t save money.
  • Pollution: FOG is a pollutant. When it gets into the water supply or out into streams and rivers, it can damage the environment and animal life. Of course, dumping grease is illegal, but causing blockages in city pipes can contribute to overflows and pollution in the local area.
  • City fines: Cities require restaurants to perform regular grease trap maintenance and document each service. You may be fined if you can’t produce evidence of grease trap maintenance at periodic inspections.
  • Loss of business: If you have a grease emergency and the patrons in your restaurant can smell it, you’ll lose customers in the short term and many people may choose never to come back.

How to Prevent Buildup of Grease and Solids

If you feel that you’re having to clean your grease trap too frequently, you can do a few simple things to minimize the amount of grease and solids going down the drain. First, line chefs should have cans available for used oil. The oil and grease can cool, and then you can recycle it or dispose of it without putting it through the trap.

To minimize solids, make sure all your servers and kitchen staff are thoroughly swiping off excess food into the garbage before putting dishes in the dish pit. To get the last bit of food scraps and oils left over on plates, have your dishwasher rinse off the dishes in cold water to solidify the oils. Use a screen over the drain to catch the last bits of food and grease that are rinsed off and throw that away.

Finally, always be sure to rinse dishes off in sinks that are connected to the grease trap. Restaurant kitchens have multiple sinks, and not all of them are connected to the trap.

If you’re still having grease trap issues while using best practices with food waste and routine grease trap cleaning, you might consider getting a larger one.

Get Professional Grease Trap Cleaning Services

By now you know that grease trap cleaning is nothing to fool around with. If it’s been a while since your grease trap has been professionally cleaned, or if your city has told you to clean it more often, reach out to our commercial plumbing team at Wm. T. Spaeder to schedule an inspection and cleaning service. Our team operates in the Erie, Pittsburgh, and Buffalo areas. We can pump out traps and interceptors as well as provide you with a full FOG report to remain up to date on grease trap system maintenance. Contact our commercial plumbing specialists today.


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