How to Clean a Grease Trap: Pump-Out Schedules, Logs, and Restaurant Rules

To clean a grease trap, you shut off water to the sinks feeding it, open the lid, skim off the floating grease, scoop out the settled solids, scrape the walls and baffles, check the inlet and outlet, replace the lid, and log the clean. Small under-sink traps are often cleaned in-house. Large in-ground grease interceptors are pumped by a licensed hauler, usually before grease and solids reach about 25 percent of the tank.

Most restaurant operators think about the grease trap only when something goes wrong: a smell in the dining room, slow floor drains, or water coming back up through the floor sink during the lunch rush. By then the problem has already cost money. A backed-up drain can force a kitchen to close, and the local sewer authority can fine a restaurant whose grease clogs the public line. The trap is a piece of plumbing, but keeping it working is a management job, with a schedule, an owner, and paperwork.

What is the difference between a grease trap and a grease interceptor?

People use the two terms loosely, but they usually describe two different pieces of equipment. The difference decides who cleans it.

Your plumbing permit or the original building plans will say which type you have and how big it is. If you are not sure, ask your local sewer or wastewater department before you open anything.

What does the FDA Food Code say about grease traps?

Very little, and that surprises people. The Food Code's grease trap rule, 5-402.12, says that if a grease trap is used, it must be located so it is easily accessible for cleaning. That is the whole requirement. The Food Code leaves sizing, pumping frequency and disposal to plumbing codes and local wastewater rules.

The Food Code matters in a different way when the trap fails. A sewage backup in a food establishment is one of the conditions the Food Code treats as an imminent health hazard, which can require you to stop operating until it is fixed. Our concept page on crisis management and imminent health hazards explains what that means in practice, and our page on equipment, water and utilities covers how plumbing fits into the Food Code more broadly.

So the honest answer to "how often" is that your local sewer authority decides, and most of them publish a fats, oils and grease (FOG) program with the rules.

How do you clean a small grease trap step by step?

This outline is for a small, indoor hydromechanical trap. Follow the manufacturer's instructions for your unit, and never enter or reach into a large in-ground interceptor.

1. Do it at a slow time. Before opening or after close, so no one is using the sinks.
2. Stop the flow. Turn off the water to the sinks that drain into the trap and let it settle for a few minutes so the grease floats to the top.
3. Protect yourself and the kitchen. Wear gloves, eye protection and an apron, and keep food, clean equipment and utensils well away from the work area.
4. Remove the lid carefully. Note the position of any gaskets and baffles so they go back the same way.
5. Measure before you clean. Use a dipstick or measuring rod to check the depth of the grease layer and the solids at the bottom. Write it down. This is how you learn whether your cleaning schedule is right.
6. Skim off the grease. Scoop the floating layer into a sealed, leakproof container.
7. Remove the settled solids. Scoop out the food waste from the bottom.
8. Scrape the walls, lid and baffles. Remove stuck-on grease and check that the inlet and outlet are clear.
9. Reassemble and restore the flow. Replace the baffles and lid, make sure the gasket seals, and turn the water back on.
10. Dispose of the waste correctly. Follow your local rules. Grease trap waste does not go down another drain or into a regular trash bag that will leak.
11. Clean up and log it. Clean the area, wash your hands, and record the date, the measurements and who did it.

Grease and food waste attract pests and create odors, so the waste containers need tight lids and a pickup schedule. Our page on garbage and waste handling covers the storage rules.

How often should a restaurant grease trap be cleaned or pumped?

Local FOG programs commonly use some version of a 25 percent rule: the trap or interceptor is cleaned or pumped before grease and solids together take up about a quarter of its capacity. Many add a calendar minimum on top. A few examples from published local programs:

• Pleasanton, California requires a grease control device to be pumped when floating and bottom solids exceed 25 percent of its usable volume.
• New Orleans requires service when a device reaches 25 percent of design capacity, or at least quarterly.
• Phoenix requires gravity interceptors to be fully pumped at least once every three months unless the city grants a variance.

Your volume and menu change the answer. A kitchen frying all day and washing heavy pans fills a trap far faster than a sandwich shop. That is why the measurements in your log matter. If you are hitting 25 percent well before the next scheduled clean, the schedule is too long.

What records should you keep?

Local programs differ, but the records inspectors and sewer authorities usually ask for look like this:

• A cleaning and maintenance log with dates, depth measurements, who did the work, and any problems found.
• Hauler manifests or receipts for every interceptor pump-out, showing the volume removed and where it went.
• Repair records for damaged baffles, lids or lines.

Keep them where a manager can find them during an inspection. Many cities can ask for them at any time, and a missing record can be treated the same as a missed cleaning.

How do you keep a grease trap from filling so fast?

The cheapest grease trap cleaning is the grease that never reaches it. Local FOG programs repeat the same best practices:

• Scrape plates, pots and pans into the trash before they go to the sink.
• Use strainers in sink drains and floor drains.
• Wipe greasy cookware with a paper towel before washing.
• Collect used fryer oil for rendering or recycling instead of pouring it down any drain.
• Do not use hot water to flush grease through. It only moves the grease farther down the line, where it cools and hardens.
• Do not rely on enzymes or bacteria additives to stretch the schedule. New Orleans' program states that these products will not reduce your pump-out frequency, and some cities restrict them.

Train every dishwasher and closer on these points. Our concept page on training and retraining staff explains how to build that into onboarding.

What do inspectors look for?

Two different inspectors may check your trap, and they look for different things.

The health inspector looks at the kitchen side: whether the trap is accessible for cleaning, whether there are odors, slow drains, or sewage backing up into floor sinks, and whether grease waste is stored in a way that attracts pests.

The sewer or FOG inspector looks at the plumbing side: the size and condition of the trap or interceptor, the grease and solids depth, your cleaning logs and hauler manifests, and whether your kitchen follows its best management practices.

For how health inspections are scored and what gets written up, see our concept page on regulatory inspections.

What this means for you

If you are a manager or operator, find out which type of grease control device you have, get your local FOG program's rules in writing, and put the trap on your master cleaning schedule with a named owner. Keep every log and manifest in one place. If you hire a hauler, check that they are licensed in your area and that the manifest shows where the waste went.

If you are staff, scrape before you rinse, use the strainers, and tell a manager about slow drains or smells early. A ten-minute report beats an emergency closure.

If you are studying for an exam, remember that a sewage backup is an imminent health hazard that can require a kitchen to stop operating, and that grease and food waste must be stored so they do not attract pests.

Frequently asked questions

Do you need to clean out a grease trap?

Yes. A grease trap only works while it has room to hold grease and solids. Once it fills, grease passes into the sewer line, where it hardens and causes blockages and backups. Local sewer authorities set cleaning or pumping schedules, and many require records showing the work was done on time.

What dissolves built-up grease in a grease trap?

Nothing reliably dissolves it in place. Hot water and chemicals only move grease farther down the line, where it cools and clogs. Several local programs also say enzyme and bacteria products do not reduce pumping frequency. The fix is physical removal: skimming, scraping, or a full pump-out by a licensed hauler.

Why does my grease trap smell bad?

A smelly grease trap is usually overdue for cleaning. Rotting food solids and grease produce odors, and the smell can come back through floor drains. A damaged lid seal or gasket can also let odors escape. Measure the grease and solids depth, clean or pump the trap, and check the seal.

How much does it cost to clean a commercial grease trap?

Costs vary widely with the size of the trap or interceptor, how full it is, how often you schedule service, local disposal fees and your area. There is no reliable national figure. Get written quotes from licensed haulers in your area and confirm what the price includes, such as the manifest and disposal.

Can restaurant staff clean the grease trap?

Staff can often clean small indoor grease traps if they are trained and follow the manufacturer's instructions. Large in-ground grease interceptors are pumped by licensed liquid waste haulers, and some local programs require that. Never let anyone enter an interceptor or confined space. Check your local FOG program for what is allowed.

Where should a grease trap be located?

The FDA Food Code requires a grease trap, if used, to be located so it is easily accessible for cleaning. Some states add stricter rules. California, for example, does not allow one in a food or utensil handling area unless the enforcement agency specifically approves it. Plumbing codes and local sewer rules set the rest.

Studying for the manager exam? Test what you know about facilities, equipment and crisis management with our ServSafe Manager practice test. For the job that sends the most grease toward the trap, see how to clean a deep fryer.

Sources

• FDA Food Code 2022 (full text, PDF), section 5-402.12 Grease Trap and the imminent health hazard provisions in Chapter 8
• FDA Food Code overview and editions
• Delaware Administrative Code 5-402.12, Grease Trap, a state adoption of the Food Code wording
• California Health and Safety Code section 114201, grease trap placement in food handling areas
• City of Pleasanton FOG Manual, the 25 percent pumping rule
• Sewerage and Water Board of New Orleans, Grease Traps 101, the 25 percent or quarterly rule and enzyme products
• City of Phoenix FOG Best Management Practices Manual, interceptor pumping frequency
• ServSafe, the training program whose manager exam covers facilities, equipment and imminent health hazards