Getting a Grease Trap

What is a grease trap?

A grease trap is a mechanical device that traps FOGs (fats, oils and grease) before they can enter a wastewater or sewer line. Rebirth services grease traps and collects used cooking oil in Southern Louisiana. FOGs are less dense than water and so rise to the top of a tank containing both. Solids, such as foodstuffs, drop to the bottom. The FOGs rise to the top and are trapped. The water continues on to the wastewater pipe and into the sewer system. The FOGs and solids are removed by pumping and hauled away for proper disposal. This keeps grease from entering and possibly clogging the municipal wastewater system. This video explains, in simple terms, exactly how grease traps work.

The terms grease trap and grease interceptor are often used to mean the same thing but more often today, a grease trap is a smaller device, inside a kitchen, handling 10 to 50 gallons per minute while interceptors are usually inground, outside and handle flow rates of much more than 50 gallons per minute.

Why you can’t put grease down the drain

FOGs harden at lower temperatures and can clog, damage and backup a sewer system causing expensive damage to restaurants, businesses and homes. Cities around the globe are fighting fatbergs and the damage they do to municipal sewer systems.

Sink strainers can help prevent solids from reaching the trap but some will still find their way into the trap and collect in the bottom of the tank. This is why regular pumping of the trap is necessary. The pumping removes the grease and the solids so wastewater can continue to flow through. The EPA and the Clean Water Act determine what is allowed to flow into a municipal water system.

These regulations in turn require Louisiana, New Orleans, Baton Rouge and Covington to implement municipal regulations to stay in compliance with EPA regulations.

The different types of grease traps

There are 3 different types of grease traps. There is the manual grease trap, sometimes called passive or hydromechanical. These tend to be smaller in-kitchen traps. The gravity based model works similarly but is usually a much larger system installed outdoors. More recent technological advances have produced the automatic grease trap system

Manual grease traps

The manual grease trap is the most common because of its low purchase price, the numerous capacities and the ease of installing it in a kitchen. A combination of heat and gravity pulls the solids to the bottom, the FOGs to the top and keeps the water in between to flow out of the tank to the wastewater system. Smaller restaurants will have this type of trap for convenience and cost. Given its smaller size, it requires frequent pumping.

Automatic grease traps

Automatic grease traps are electro-mechanical devices that skim the grease and oils that float to the top and deposit them into a bin for easy disposal. These are much more costly than manual traps but have much lower operating costs due to needing much less frequent pumping.

This video illustrates the operation of an automatic grease trap.

Gravity Based Interceptor

The gravity based interceptor works on many of  the same principles as the manual grease trap. Usually outdoors and underground, it can handle a much higher volume of FOGs and water than a manual grease trap. You will need an expert with a large pumper truck to do the work of pumping the grease and solids from the interceptor.

Which type of grease trap do I need?

The first consideration is how much oil do you expect to go through? How many fryers will you have? Are you primarily a fry shop putting out huge quantities of chicken, fish or fries or are there only a couple of menu items that require deep fat frying? If you’ve got 6 to 10 fryers in use at all times you may want to opt for a larger gravity based system. If you are an occasional fryer you can probably be fine with a manual indoor grease trap.  And if you have the funds, definitely consider the hydromechanical trap for the lower operating costs.

Of course you also have to consider space and location. Indoors? Outdoors? How much space do I have?

How to buy a grease trap?

To do this right you will need expert help. You can buy a trap from some licensed plumbers, or specialized manufacturers or home stores like Home Depot. But then you have to hire someone to install it. You will want to get expert help prior to purchasing your trap. You will also want to consult local regulatory authorities to determine if they have a rule or preference for the type of trap you need to install. Many authorities now prefer the outdoor interceptor or an electro-mechanical trap for the higher efficiency in removing FOGs which can mean 90-100% removal of grease.

How much does a grease trap cost?

Smaller capacity manual traps (1 to 100 gallons) will cost between $250 to $1500 and larger capacity manual traps (750-1500 gallons capacity) between $4000 and $4800. Installation costs can run from $500 to several thousand dollars. You will also need to file for permits and inspections before installing.

Automatic grease traps, depending on size can range from $3000 to $8500 in price. Installation costs can run $500 to $3500 additional.

How large a grease trap do I need?

In theory, a grease trap is sized by the incoming flow to the trap and local plumbing codes.

The question of how determining the size of your grease trap gets answered in many different ways, usually with a large number of calculations. Here is an excerpt from the Uniform Plumbing Code as presented in Orange county California.

Or you could take this approach:

The Louisiana State Plumbing Code provides this handy chart for estimating the size of the grease trap you need.

The easy answer is you need a professional to help you size your interceptor. You may need a representative of the interceptor manufacturer to assist or, at the very least, a licensed plumber with a strong history of installing grease traps.

Louisiana Plumbing Code for installation of traps/interceptors

Each step, the grease tap size, the location of the installation, the approval to install requires written approval of a plumbing official of the state of Louisiana. A two-way cleanout shall be required on the discharge line immediately downstream of an interceptor.

Louisiana Plumbing Code for maintenance of traps/interceptors

Louisiana does not specify how often a grease trap/interceptor must be pumped and cleaned. It merely says they shall be maintained in efficient operating condition by periodic removal of the grease and solids. Other regulations require the implementation of best management practices, employee training and the documentation of maintenance and required records. Adherence to the 25% rule is a best management practice.

How to repair a grease trap?

The waste water coming into a grease trap is acidic and destructive. If you find your trap is leaking and appears corroded you will want to hire a professional and likely replace the whole trap. Generally a plastic trap is preferred over metal to prevent corrosion.

Do I need a grease trap?

Operating a restaurant without a grease trap can get you in a lot of trouble. Fines, cleanup costs, shutdown of the restaurant, lawsuits are a few of the potential outcomes from operating without a functioning grease trap. And allowing FOGs to flow into the municipal waste system can result in:

Supplemental Local Grease Trap Ordinances

Many localities such as Orleans Parish and their Sewerage and Water Board have regulations which are in addition to those of Louisiana. Orleans Parish has a new regulation, Pretreatment Ordinance 16.5 which provides specific rules governing FSEs (food service establishments. It states that each FSE shall:

Best Management Practices can be hard to find. Here are best management practices from Sewerage and Water Board of Orleans Parish:

  1. Scrape food scraps into the trash
  2. Avoid using the disposal
  3. Use sink strainers
  4. Wipe greasy utensils and dishware with paper towels before washing
  5. Recycle fry oil and cooking grease
  6. Bacterial and enzyme products will not decrease your pump our frequency
  7. Keep manifests on site for 3 years

And, of course, when it comes to pumping out your interceptor adhere to the 25% rule, which says pump before the trap reaches 25% of design capacity or at least quarterly.

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