grease - faq
(Frequently Asked Questions)
MCelroy Plumbing & Heating co., inc.
serving Mississippi and alabama

"GREASE IS THE WORD"
An article giving details about GREASE REMEDIATION.
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Frequently Asked Questions About Grease:

In the sewage collection and treatment business, the answer is an emphatic YES! Grease is singled out for special attention because of its poor solubility in water and its tendency to separate from the liquid solution.

Large amounts of oil and grease in the wastewater cause trouble in the collection system pipes. It decreases pipe capacity and, therefore, requires that piping systems be cleaned more often and/or some piping to be replaced sooner than otherwise expected. Oil and grease also hamper effective treatment at the wastewater treatment plant.

Grease in a warm liquid may not appear harmful. But, as the liquid cools, the grease or fat congeals and causes nauseous mats on the surface of settling tanks, digesters, and the interior of pipes and other surfaces which may cause a shutdown of wastewater treatment units.

Problems caused by wastes from restaurants and other grease-producing establishments have served as the basis for ordinances and regulations governing the discharge of grease materials to the sanitary sewer system. This type of waste has forced the requirement of the installation of preliminary treatment facilities, commonly known as grease traps or interceptors.

A trap is a small reservoir built into the wastewater piping a short distance from the grease producing area.  Baffles in the reservoir retain the wastewater long enough for the grease to congeal and rise to the surface. The grease can then be removed and disposed properly. 

An interceptor is a vault with a minimum capacity of between 500 and 750 gallons that is located on the exterior of the building. The vault includes a minimum of two compartments, and flow between each compartment is through a 90° fitting designed for grease retention. The capacity of the interceptor provides adequate residence time so that the wastewater has time to cool, allowing any remaining grease not collected by the traps time to congeal and rise to the surface where it accumulates until the interceptor is cleaned. 

Refer to Grease Trap and Interceptor Maintenance.

All grease interceptors should be cleaned at least twice each year. Some establishments will find it necessary to clean their traps more often than twice per month. If the establishment is having to clean it too often, the owner should consider installing a larger trap or interceptor.

If the establishment is uncertain whether it has a grease trap, the owner should contact the local sewer agency or McElroy to assist in determining if you have a properly functioning Interceptor and what size.

Any establishment that introduces grease or oil into the drainage and sewage system in quantities large enough to cause line blockages or hinder sewage treatment is required to install a grease trap or interceptor. Interceptors are usually required for high volume restaurants (full menu establishments operating 16 hrs/day and/or serving 500+ meals per day) and large commercial establishments such as hotels, hospitals, factories, or school kitchens. Grease traps are required for small volume (fast food or take-out restaurants with limited menus, minimum dishwashing, and/or minimal seating capacity) and medium volume (full menu establishments operating 8-16 hrs/day and/or serving 100-400 meals/day) establishments. Medium volume establishments may be required to install an interceptor depending upon the size of the establishment.

The Uniform Plumbing Code requires that no grease trap have a capacity less than 20 gallons per minute (gpm) or more than 55 gallons per minute (gpm). The size of the trap depends upon the number of fixtures connected to it. The following table provides criteria for sizing grease traps:

If the establishment uses grease and oil in food preparation, it will eventually encounter a maintenance problem with a plugged building sewer line. The blockage can create a sewer backup situation and ultimately a potential health problem in the establishment. Someone will have to pay for removing the blockage. If the problem is in the building sewer line, then the establishment has direct responsibility for paying for the maintenance. If the blockage or restriction is in the public sewer main and it can be proven that the establishment is the cause of the blockage, then the establishment may have to pay for the public sewer to be maintained. Blocking a sanitary sewer line is also a violation of the federal Clean Water Act.

When waste pretreatment is required by the State or City, an approved grease trap or interceptor shall be installed according to the Uniform Plumbing Code. The rules of the Health Department and your municipal sanitary sewer agency will also assist the establishment in determining if a grease trap or interceptor is required. All administrative authorities prohibit the discharge of materials that can solidify and create blockages in the wastewater collection system or treatment plants. The Health Department makes periodic inspections to see that no health problems exist due to improperly maintained grease interceptors. These rules will be enforced if a problem exists.

 How can I get in compliance?

The establishment should contact its local jurisdiction. The establishment will be asked to purchase a permit for the grease trap. This will enable the proper jurisdiction to assist the establishment in cleaning schedules and advise them of a problem showing up in the wastewater collection system. A grease interceptor permit is required regardless of whether the establishment has an existing trap or is installing a new one.

All food service establishments suspected of causing problems to the collection system or treatment facilities will be inspected.  Some agencies use the following criteria to inspect grease traps:

If the trap is in FAIR condition, the establishment should be advised to keep an eye on the maintenance schedule. The cleaning frequency may need to be increased. If the trap is in POOR condition, the establishment should be issued a compliance order to have it cleaned immediately. The establishment should then be required to contact the issuing authority within 30 days to verify that the grease interceptor has been properly cleaned.