What a grease trap is and how you start the work

Last updated 2026-08-21

What is a grease trap?

A grease trap is a tank or box on a kitchen drain that holds back fats, oils, and grease (FOG) so they do not ride into a sewer or a septic tank. Water slows down inside. Grease floats. Food solids sink. The clearer middle layer leaves through an outlet baffle.

People use the same two words for two different boxes. Under-sink hydromechanical units are small, often 10 to 50 gallons, and they live inside the kitchen. Outdoor gravity interceptors are large concrete or fiberglass tanks, often 750 to 2,000 gallons or more, buried in the lot. Both run on the same physics. Codes treat them as different products.

They exist because FOG cools in pipes, sticks to the walls, and grabs wipes and rags. That plug is a common way sanitary sewers fail. EPA estimates at least 23,000 to 75,000 sanitary sewer overflows per year, not counting backups into buildings.^[10] Pretreatment rules tell sewer plants to keep viscous junk out of the collection system. The federal line is blunt. 40 CFR 403.5 prohibits "solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW resulting in interference."^[1]

If you are entering this work, the trap is the job site. You install it, you pump it, or you do both. The paper path is not national. It is a city pretreatment file plus a state hauler rule. Confirm both.

Who requires a grease trap in the first place?

Food service kitchens need grease traps because the plumbing code and the sewer utility both say so. Almost every restaurant, cafeteria, and commercial kitchen on a public sewer will be told to install an interceptor and keep it pumped. The utility can fine the kitchen or cut service if FOG leaves the building.

EPA's National Pretreatment Program, run under the Clean Water Act, is why those local FOG ordinances exist. Publicly owned treatment works write local limits and then push the grease back onto the generator.^[2][3] Plumbing codes set how the box is built. Many states use International Plumbing Code Chapter 1003 or the Uniform Plumbing Code interceptor chapter. You still read the edition your city adopted, not a blog summary.

On a septic system the health department owns the rule. Massachusetts Title 5 is a clean example. Grease traps are required for kitchen flows at restaurants, nursing homes, schools, and hospitals, with a 1,000 gallon minimum and at least 24 hours of detention for the kitchen flow.^[4] Florida's onsite sewage rule sets a 750 gallon minimum volume for many grease interceptors.^[5]

If the kitchen is on city sewer, call the pretreatment coordinator. If it is on a septic tank, call county health. Do not guess from a national checklist.

Setting	Who writes the rule	What usually triggers it
Public sewer	POTW pretreatment plus the plumbing code	A food service sewer connection
Onsite septic	State or county health code	Restaurant or cafeteria kitchen flow
Used fryer oil (yellow grease)	State agriculture or renderer program	Inedible kitchen grease, not trap sludge

How do you start grease trap work?

Pick a lane first, then chase the paper that lane actually uses. Pumping existing traps is a hauler business. Setting new tanks is plumbing or excavation. A few people do both. They are not the same license stack.

For pumping, form the business the way your state requires (entity papers, EIN, local tax certificate). Then register as a waste transporter if your state keeps that list. Texas is direct. A person who transports grease trap waste "shall register with the executive director."^[6] California splits yellow grease into a CDFA inedible kitchen grease registration that is not the same thing as a city FOG pumper permit.^[7] You also need a written outlet, meaning a plant or processor that will take the load. No outlet, no legal route.

For install work you are usually under the plumbing contractor board, plus a building permit for each tank. I would not start on buried interceptors without a licensed plumber on the ticket. Inspectors fail unpermitted tanks. That failure lands on you.

Then comes insurance, a vacuum truck or a written lease on one, confined-space gear if anyone's head goes in a hatch, and a manifest pad. The first paying job should wait until the transporter number or the plumbing license is actually in hand. Confirm processing with the board that issues it. Nobody honest can quote their backlog.

If you are still choosing this work against other outdoor trades, read grease trap vs nearby career.

Do you need a license to pump grease traps?

Usually yes, but there is no single national grease-trap card. Most states fold trap waste into septage, special waste, or liquid-waste transporter registration. Some cities add a FOG hauler permit on top of that.

Texas registration under 30 TAC 312.142 is the clean statutory example.^[6] Massachusetts requires a licensed septage hauler to clean Title 5 grease traps.^[4] California's inedible kitchen grease program covers fryer oil and similar material, and cities still run their own interceptor pumper lists.^[7] You confirm the list you will actually appear on.

You may also need a commercial driver's license if the truck's gross vehicle weight rating hits the federal threshold. Group B is the usual bucket once a vehicle is 26,001 pounds or more, under 49 CFR 383.91. Confirm the truck you will buy, not a forum average.^[12] A plumber's license still applies if you open the building drain or set a new interceptor.

I would not take a route under the table for a restaurant group. The kitchen's pretreatment file will ask for your hauler ID and the disposal ticket. That is how people get caught.

Credential stacks vary by state. Later writeups in this series walk individual comparisons, including grease trap guide 12 and grease trap guide 24.

What paper do you carry on the first job?

On the truck you want the hauler registration, the vehicle authorization if the state issues one, insurance cards, and a manifest or trip ticket for every load. The restaurant wants a copy for its FOG file. The plant wants a copy. You keep a copy.

A manifest is the chain of custody. Generator name and address, date, gallons, trap location, your company and permit number, the receiving facility, signatures. Some pretreatment programs specify the form. Some accept a standard liquid-waste ticket. Confirm the form. Do not invent one the coordinator has never seen.

If you want a single binder that already maps interceptor ID, pump dates, and manifest copies, GreaseTrapPath sells a $199 one-time Interceptor + Manifest Kit. Use it or build the same stack in a cheap binder. The board does not care about the cover.

Also carry the kitchen's account notes. Trap size. Last pump date. Which lid is actually the interceptor. Show up guessing and you pump the storm sump by mistake.

Is a grease trap the same as a grease interceptor?

In the field, people mix the words. "Trap" often means the small indoor unit. "Interceptor" often means the big outdoor gravity tank. Plumbing codes use both terms and hang test standards on them (PDI G101 and ASME A112.14.3 for many hydromechanical units).

Hydromechanical grease interceptors are compact. They use baffles, and they are rated in gallons per minute and grease capacity in pounds. Gravity grease interceptors are large-volume tanks that rely on detention time. Outdoor gravity tanks are what most city FOG programs want on a full restaurant line.

Why it matters when you start: pumping a 20 gallon under-sink unit is a bucket job some plumbers still do. Pumping a 1,500 gallon interceptor is a vacuum truck and a disposal ticket. Your insurance, your permit, and your price are not the same.

Sizing is local. Florida's onsite rule uses a 750 gallon floor for many grease interceptors.^[5] Massachusetts Title 5 uses a 1,000 gallon floor and 24-hour detention for kitchen flow.^[4] City sewer programs often size off fixture counts or seats. Confirm the table in the ordinance you are working under. A longer pass through interceptor types is in grease trap guide 36.

How often does a grease trap need to be pumped?

Pump on the 25 percent rule and the ordinance, not on what the kitchen wants to save. Many FOG programs and onsite codes use the same trigger. Grease plus solids hit about a quarter of the wetted depth, or a fixed calendar comes due, whichever lands first.

Massachusetts Title 5 requires grease traps to be inspected monthly and cleaned at 25 percent of effective depth or at least every three months, whichever is sooner.^[4] That 90-day ceiling shows up in a lot of city FOG manuals too. It is not a federal interval. EPA does not publish a national pump calendar.^[2][11]

Under-sink units can load up in a week on a fry line. An oversized outdoor tank at a sandwich shop might still look clean at 90 days. Measure the layers. Do not bill on a story.

I would refuse a customer who wants a once-a-year outdoor pump if the local rule is quarterly. You inherit the violation when your ticket is the only one in their file.

What happens to grease trap waste after you pump it?

It goes to a facility allowed to take brown grease. That is usually a wastewater plant with a receiving station, a dedicated FOG processor, or in some regions a renderer that accepts trap waste. It is not yellow grease. Yellow grease is used fryer oil. Mixing them can get a load rejected and can trip an inedible kitchen grease rule.^[7]

You do not dump it in a ditch, a storm inlet, or another restaurant's interceptor. That is illegal disposal. Clean Water Act liability sits with the generator and can sit with you.^[3]

Some plants charge a per-gallon receiving fee. Some require an appointment and a contamination check. Get the receiving rules in writing before you price a route. If the only plant in an 80 mile radius is closed on weekends, your Saturday accounts just got more expensive.

Dewatering and composting shops exist in some states. They still need the right residual-waste or solid-waste authorization. Confirm the outlet, then confirm it again the week you start, because plants change acceptance lists.

What safety rules apply when you open a trap?

Treat an outdoor interceptor as a confined space until a competent person says it is not. OSHA's rule is not optional if you have employees. The standard defines a confined space as one that "is large enough and so configured that an employee can bodily enter and perform assigned work," has limited entry and exit, and "is not designed for continuous employee occupancy."^[8] Plenty of interceptor vaults meet that test.

The air can kill you. Hydrogen sulfide builds over rotting FOG and sludge. NIOSH lists H2S as a gas that can drop a person with little warning in pits and sewers.^[9] You need air monitoring, a retrieval plan, and a trained attendant before anyone goes in. Most pumping jobs should not put a body in the tank at all. Vacuum from grade. Break the crust with the boom.

Other real hazards: splash in the eyes, pathogens in the waste, traffic if the lid sits in a drive lane, and back strain from indoor cassette traps. A face shield is cheap.

I would budget confined-space training and a four-gas meter before I hired the second person. Read 29 CFR 1910.146 before you write a job hazard note.^[8]

How much money do you need to start grease trap work?

Nobody has a clean national average I would trust. Used vacuum trucks change hands in a wide band that runs from the mid five figures into six figures, depending on tank gallons, year, and whether the pump actually works. I will not invent a sticker price. Price the truck in front of you.

Add pollution liability from a broker who knows waste haulers, plus auto and workers' comp. Ask the receiving plant if they want a disposal bond. Cash you will actually burn in month one is fuel, dump fees, hoses, a pressure washer, replacement gaskets, and the state registration charge. Confirm that charge on the agency page. It moves.

If you cannot park a dripping truck, you also need a yard the zoning office accepts. Starting as a one-truck owner-operator with a contracted dump site is the usual path. Buying a "route" can be fine if you verify every account's ordinance status and last inspection. Paying a premium for a spreadsheet of restaurant names is often a waste.

For first-year cost shape against nearby trades, see grease trap vs nearby career and the equipment notes in grease trap guide 48.

What should you confirm with the board before you take a route?

Call the pretreatment coordinator (sewer) or the health department (septic) and ask five things. Who must hold the hauler credential. Which manifest they want. Which plants they accept. The pump-out interval they enforce. Whether you must sit on an approved pumper list before a kitchen can use you.

Then call the state transporter desk. Ask if grease trap waste is on their registration and whether the truck needs an inspection sticker. Texas and a lot of other states put grit trap waste and grease trap waste on the same form.^[6] California kitchens may also ask if you are on the city FOG hauler list and whether yellow grease is in your scope.^[7]

Write down the person's name, the date, and the form numbers they cite. Boards swap PDFs. A screenshot of last year's fee is not evidence.

GreaseTrapPath is an independent publisher, not a law firm and not a service company. If you want the kit and the checklist in one place, start at /start. Still confirm every blank with the board that signs the permit.

Can you start with just a truck and a pump?

A truck and a pump without paper is how you buy a fine. The mechanical work is not the hard part. The hard part is being the named hauler on a ticket the city will file.

Minimum I would want before the first gallon: a legal entity, the transporter or septage credential your state requires, insurance the plant and the kitchen will accept, a receiving facility that has said yes in writing, and a manifest process. If the truck is over the CDL weight, the right license too.^[12]

You can subcontract a permitted hauler while your registration is pending if the board allows it. Confirm that. Do not put your name on a load you cannot legally carry.

Indoor cassette service is a smaller start. Van, barrels, a transfer site. It still needs the same waste paperwork in most cities. There is no clean indoor-only exemption I would trust without reading the ordinance.

More on first-year operations sits in grease trap guide 60 and grease trap guide 72.

Frequently asked questions

What is grease trap?

A grease trap is a tank on a kitchen drain that slows wastewater so fats, oils, and grease float and food solids settle. Cleaner water leaves through a baffle. Small indoor units and large outdoor interceptors both count. Cities and health departments require them so FOG does not clog sewers or septic fields. Confirm the device type in the local ordinance.

How do you start grease trap?

Pick pumping or install work, then collect that lane's paper. Form the business, get the state waste-transporter or plumbing credential your board actually issues, lock a legal dump site, carry manifests, and buy insurance the plant will accept. Do not take a load until the number is in hand. Confirm forms and fees with the issuing board. No one can promise processing time.

Is a grease trap the same as an interceptor?

Field slang treats "trap" as the small indoor box and "interceptor" as the buried gravity tank. Codes use both words and attach different test standards. Hydromechanical units are rated in gpm and pounds of grease. Gravity tanks are sized in gallons and detention time. Your permit, truck, and price change with the box. Read the ordinance's definitions, not a catalog headline.

Who hauls grease trap waste?

A registered liquid-waste or septage hauler, sometimes also listed on a city FOG pumper roster. Texas requires transporter registration for grease trap waste under 30 TAC 312.142. Massachusetts wants a licensed septage hauler on Title 5 traps. California adds a separate inedible kitchen grease path for yellow grease. Confirm which list your city files with the kitchen's pretreatment paperwork.

Do restaurants have to have grease traps?

Most food service kitchens on a public sewer must install and maintain one because the plumbing code and the sewer utility both require it. Kitchens on septic systems often fall under state onsite rules, such as Massachusetts Title 5 or Florida Chapter 64E-6. The trigger is kitchen wastewater with FOG, not the word "restaurant" on the sign. Ask pretreatment or county health.

How full can a grease trap get before pumping?

Many codes use 25 percent. When grease plus solids reach about a quarter of the effective depth, it is time to pump, even if the calendar has not run out. Massachusetts Title 5 also caps the interval at three months and requires monthly inspections. Your city may use 90 days, 25 percent, or both. Measure the layers. Do not guess from the smell.

Is grease trap waste hazardous waste?

Usually no. Brown grease is typically handled as special waste, septage, or liquid industrial waste, not as listed hazardous waste. That does not make illegal dumping legal. A load contaminated with solvents or a lot of petroleum can change the picture. The receiving plant's acceptance rules control what you can tip. Ask them in writing before you price the account.

Can I dump grease trap waste at a wastewater plant?

Only if that plant is authorized to receive it and has accepted you as a hauler. Many POTWs run a receiving station with hours, a per-gallon fee, and a manifest check. Some will not take trap waste at all. You need that yes in writing. A plant that takes septage may still reject brown grease. Confirm the waste type on their ticket.

Do I need a CDL to haul grease?

You need a CDL when the truck meets the federal commercial motor vehicle definition, commonly a GVWR of 26,001 pounds or more under 49 CFR 383. Many full-size vacuum trucks sit in that band. A small trailer unit may not. Confirm the rating plate on the truck you will actually drive, plus any state tanker or air-brake endorsements. Do not trust a seller's shrug.

What is a grease manifest?

It is the trip ticket that follows the load from the kitchen to the plant. Typical fields are generator name, address, date, gallons, trap ID, your permit number, the receiving facility, and signatures. The kitchen keeps a copy for its FOG file. You keep a copy. The plant keeps a copy. Use the form the pretreatment office named, not a blank invoice.

How big is a typical under-sink grease trap?

Indoor hydromechanical units often run about 10 to 50 gallons and are rated in gallons per minute, more than tank volume. They sit under a sink or in a closet and fill fast on a fry line. Outdoor gravity interceptors are a different product, often 750 gallons and up. Do not price or permit them as if they were the same box.

What is FOG in a grease trap?

FOG means fats, oils, and grease from kitchen wastewater. It floats when the water slows, which is the whole point of the tank. In pipes it cools, sticks, and grabs solids until the line blocks. EPA pretreatment rules treat that blockage risk as interference at the sewer plant. Local FOG ordinances are how cities push the cleanup back onto the kitchen and its hauler.

Are outdoor interceptors permit-required confined spaces?

Many meet OSHA's confined-space definition in 29 CFR 1910.146 because a person can bodily enter, the hatch is a limited exit, and the tank is not built for occupancy. Hydrogen sulfide makes the air a real killer. Most pump jobs should stay outside the tank. If someone must enter, you need the permit, the meter, and an attendant. Train before you hire.

Sources

1. eCFR, 40 CFR 403.5 National pretreatment standards: Prohibited discharges: Federal pretreatment rules prohibit solid or viscous pollutants in amounts that cause obstruction and interference at a POTW.
2. U.S. EPA, Introduction to the National Pretreatment Program (2011): EPA's National Pretreatment Program is the federal framework POTWs use to control industrial and commercial discharges, including FOG programs.
3. U.S. Government Publishing Office, 33 U.S.C. § 1317 toxic and pretreatment effluent standards: Clean Water Act section 1317 is the statutory hook for federal pretreatment standards that local FOG rules implement.
4. Massachusetts 310 CMR 15.000, Title 5 State Environmental Code: Title 5 requires grease traps for many institutional and restaurant kitchen flows, with a 1,000 gallon minimum, 24-hour detention, monthly inspection, and cleaning at 25 percent or every three months.
5. Florida Administrative Code Rule 64E-6.013: Florida's onsite sewage rule sets a 750 gallon minimum volume for many grease interceptors.
6. Texas Administrative Code, 30 TAC §312.142 Transporter Requirements: Texas requires a person who transports grease trap waste to register with the TCEQ executive director.
7. California Department of Food and Agriculture, Inedible Kitchen Grease program: California registers transporters of inedible kitchen grease separately from city FOG interceptor pumping programs.
8. OSHA, 29 CFR 1910.146 Permit-required confined spaces: OSHA defines a confined space as large enough to bodily enter, with limited entry and exit, and not designed for continuous occupancy.
9. NIOSH Pocket Guide to Chemical Hazards, hydrogen sulfide: NIOSH documents hydrogen sulfide as a toxic gas associated with sudden collapse risk in pits and similar spaces.
10. U.S. EPA, Sanitary Sewer Overflows (SSOs): EPA estimates at least 23,000 to 75,000 sanitary sewer overflows per year, not including backups into buildings.
11. U.S. EPA, National Pretreatment Program overview: EPA runs the National Pretreatment Program through local POTWs and does not publish a national grease trap pump-out calendar.
12. eCFR, 49 CFR 383.91 Commercial motor vehicle groups: Federal CDL Group B generally applies to vehicles with a GVWR of 26,001 pounds or more, which catches many vacuum trucks.