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There Is No National Grease Limit

Almost everything written about grease traps quotes a figure as though it applied everywhere. It does not, and the difference is not small.

The short form

Federal law prohibits discharging to a sewer solid or viscous pollutants in amounts that will cause obstruction, but it sets no grease number. Each publicly owned treatment works must develop and enforce its own specific local limits, and EPA’s training examples range from 50 to 600 milligrams per liter.

Source: 40 CFR 403.5, National pretreatment standards: Prohibited discharges; U.S. EPA, FOG Management and Control Program.

InterceptorCall is a referral service, not a contractor. We connect operators and property managers with independent contractors. Contractors and waste haulers are required to hold whatever credential and permit their state or municipality demands — ask to see them, because the manifest they leave you is a compliance record. We carry out no work, we haul nothing, we do not set prices, and we never charge the caller anything. Nothing here states the grease limit, the pumping interval or the device size that applies to any particular kitchen; those are set by your control authority and by your installation.

What the federal rule actually says

Under the National Pretreatment Program, a user may not introduce into a publicly owned treatment works any pollutant which causes pass through or interference. Among the specific prohibitions is one aimed squarely at grease: solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW resulting in interference.

Read what is not there. No milligrams per liter. No gallons. No interval. The federal rule states an outcome that is forbidden, not a threshold you can measure yourself against.

Source: 40 CFR 403.5, National pretreatment standards: Prohibited discharges.

Where the number comes from instead

The same regulation requires each POTW with an approved pretreatment program to develop and enforce specific limits implementing those prohibitions. That is the sentence that decides your life: the enforceable figure is written locally, by the authority that owns the sewer your building drains into.

It sits in a sewer use ordinance, and it is a public document.

How different those numbers are

EPA’s own training material for pretreatment programs lists local oil and grease limits from real authorities, and the spread is startling: 50 milligrams per liter in one, 200 in another, 275 or 325 depending on test method in a third, and 600 in a fourth.

50 to 600milligrams per liter — the range of local oil and grease limits in the examples EPA uses in its own pretreatment training

A twelve-fold spread on the one figure an operator is judged against. Any article that hands you a single number has quietly picked one city and not told you which.

Source: U.S. EPA, FOG Management and Control Program.

The two other prohibitions worth knowing

The same section forbids discharges with a pH lower than 5.0 unless the works is specifically designed to accommodate them, and heat in quantities that push the treatment plant above 40 degrees Celsius, which is 104 Fahrenheit.

The second one matters in a kitchen for a reason that is not obvious and has nothing to do with the treatment plant. Hot water is the most common way a working device stops working.

What to do with all this

Find out who your control authority is — the sewer authority, not the water utility, and in many places not the city either. Ask for the sewer use ordinance and the FOG program requirements. Ask what limit applies to your classification of establishment and what they expect to see at an inspection.

Half an hour on the telephone replaces every general article on this subject, including this one.

Have the last manifest in front of you.Date, hauler, volume removed and where it went — it is the first thing anyone asks for and it tells a contractor more about the state of the vessel than a description does. We will route you to somebody who covers your area, identified from the ZIP code of the premises, and you are never charged. Other plumbing work at the premises can be arranged through the same call.

Call (888) 753-1770