Grease trap guide 86 and the real paper path start

Last updated 2026-08-21

What is a grease trap?

A grease trap is a tank or box in the drain line that slows kitchen wastewater so fats, oils, and grease (FOG) cool, float, and stay put instead of coating the sewer. Food solids drop. The clearer water in the middle leaves toward the building drain or the septic tank.

People say "grease trap" for the small indoor steel unit under a three-compartment sink. Codes often call the big outdoor concrete tank a gravity grease interceptor. Field inspectors still say trap for both. Do not fight the noun. Learn which device your plan reviewer will stamp.

The legal reason the box exists is not a restaurant myth. Federal pretreatment rules tell a publicly owned treatment works it cannot take solid or viscous pollutants in amounts that obstruct the plant or the pipes. 40 CFR 403.5(b)(3) says those pollutants "shall not be introduced into a POTW" when they will "cause obstruction to the flow in the POTW resulting in Interference." ^[1] Grease is the viscous pollutant cities have in mind.

The FDA Food Code treats the device as something you may use, then it gets strict about access. Section 5-402.12 states, "If used, a GREASE TRAP shall be located to be easily accessible for cleaning." ^[2] If the lid sits under a dishwasher you cannot roll away, you already failed the inspection that matters.

I treat a grease trap as plumbing first and a wastewater file second. Buy a box and never join it to a FOG program, and you bought a buried trash can. The paper is the job. The steel is just the hardware.

How do you start grease trap work the right way?

You start on paper, not at the supply house. I would not order a tank until three people say the same size out loud: the plumber who stamps the drawing, the city or county plan reviewer, and the sewer authority (or the onsite reviewer if you are not on a public sewer).

Write down the discharge path first. Public sewer means the International Plumbing Code or a Uniform Plumbing Code chapter on interceptors, plus whatever FOG ordinance the POTW adopted. ^[3][4] Onsite systems follow the state septic code. Massachusetts Title 5 is the clearest published example. 310 CMR 15.230 requires grease traps for kitchen flows at restaurants, nursing homes, schools, hospitals, and other sites that will send grease, and it sets a 1,000 gallon floor with a 36 hour hydraulic detention time. ^[5]

Next, list every fixture that can carry grease. Pot sinks, wok ranges, and cook-line floor drains count. The dishwasher is a local fight. Some reviewers want it tied in. Some ban it because the heat melts FOG and shoves it through the trap.

Then apply for the plumbing permit and, if the POTW runs a FOG program, the interceptor registration. Confirm the current form and fee with that board. I will not invent a fee or a processing clock. Boards change both.

Install to the approved drawing. Schedule the first pump. Keep the manifest. That is how you start grease trap work. Hardware without a file is how people fail the opening inspection.

For a companion walkthrough of first-year paper, use Grease trap guide for first-year operators and paper and Grease trap guide 76 and your first-year paper path.

Who regulates grease traps, the city or the feds?

Your plumbing official and your sewer authority regulate the grease trap. There is no federal grease trap bureau and no national operator license.

EPA writes the frame. 33 U.S.C. § 1317 lets EPA require pretreatment so commercial and industrial waste does not pass through or interfere with a POTW. ^[6] 40 CFR 403.8 then requires a pretreatment program at POTWs with a total design flow over 5 million gallons per day that receive industrial pollutants which pass through or interfere, and at some smaller plants on a case-by-case finding. ^[7] EPA's own introduction to that program is the document most FOG coordinators were trained on. ^[9]

Your kitchen is usually not a Significant Industrial User. You still sit under the local FOG ordinance the POTW wrote so it can meet 40 CFR 403.5. That is why two towns 20 miles apart can demand different tanks and different pump intervals.

If the kitchen drains to a septic tank, the state onsite code wins. Title 5 in Massachusetts is not optional language. It names the facilities, the minimum volume, the detention time, and the inspection cycle. ^[5] Wisconsin puts interceptor construction in SPS 382.34 of the state plumbing code, a different statute family than a sewer-use ordinance. ^[10]

Confirm the current reviewer with the building department and the water reclamation district. I have watched operators file only a plumbing permit and then fail the FOG walk-through the week before opening. Nobody has good data on every local FOG ordinance in one chart. The closest federal picture is EPA pretreatment guidance, and it still sends you back to the POTW. ^[9]

Is a grease trap the same thing as a grease interceptor?

In the field, yes. In the code book, not really. A hydromechanical grease interceptor is the compact indoor unit with baffles and a flow-control fitting. A gravity grease interceptor is the large in-ground tank that wins by volume and time. An automatic grease removal device skims FOG on a timer or a sensor.

IPC Chapter 10 is the model language a lot of cities adopt. It requires a grease interceptor or automatic grease removal device to take drainage from fixtures and equipment with grease-laden waste in food prep areas. ^[3] California's plumbing code (UPC based) keeps traps and interceptors in Chapter 10, so a California plan check will not look like an IPC state even when the physics is the same. ^[4]

I buy a gravity interceptor for a fry-heavy restaurant when the site can take a vault. Indoor hydromechanical units are fine for a small cafe if the flow control is actually installed and the cleaning interval is honest. Automatic skimmers cost more to keep alive. I would not spend on one unless the room or the health inspector forces it.

Type	Typical spot	How it holds FOG	Code hook you will see
Hydromechanical interceptor	Indoors, near the sink	Baffles plus external flow control	IPC 1003 [3]
Gravity interceptor	Outdoors, in ground	Long detention, large volume	IPC 1003, CA Chapter 10 [3][4]
Grease removal device	Indoors, powered skim	Timed or heated removal	IPC 1003 automatic devices [3]

Call it whatever the reviewer calls it on the comment letter. Winning the vocabulary argument does not open the restaurant.

What size grease trap do plumbing codes actually require?

There is no single national size. Model plumbing codes size indoor units by flow rate or drainage fixture units. Gravity tanks are sized by detention time, connected fixtures, or a local worksheet the FOG program hands you. Confirm the method with the board that stamps the plan.

Massachusetts 310 CMR 15.230 requires a minimum 1,000 gallon grease trap and a 36 hour hydraulic detention time, with a minimum depth of four feet, when Title 5 applies to the kitchen. ^[5] That number is real, and it is not a restaurant-on-city-sewer rule. It is an onsite-system rule. People paste it into city-sewer jobs and then get a correction letter. Do not do that.

IPC 2021 Chapter 10 is the document I open first in an IPC state, then I check the city's amendments. ^[3] California reviewers open Chapter 10 of the California Plumbing Code. ^[4] Wisconsin reviewers open SPS 382.34. ^[10] Manufacturer sizing software is a draft, not an approval.

Operators undersize indoor units when they trust a sales sheet more than the fixture list. That is a waste of money. The cheap 20 gpm box under a hotel banquet sink will pass the opening day photo and fail the first grease sample. Spend on the tank the reviewer already said they will accept.

For how local dollars move once you leave the model code, the state cost explainers beat a national average. Start with grease trap cost in california or grease trap cost in florida if that is your site.

How often do you have to pump a grease trap?

Pump when the combined FOG and settled solids hit about 25 percent of the wetted depth, or sooner if your ordinance sets a calendar maximum. Measure the blanket. Do not worship the calendar.

Massachusetts is again the clean published rule. 310 CMR 15.351 tells the owner to inspect monthly and to have a licensed septage hauler clean the trap whenever grease is 25 percent of the effective depth, or at least every three months, whichever is sooner. ^[5] Plenty of city FOG ordinances copied that 25 percent line even when they are not Title 5 towns.

EPA's food-service FOG fact sheet is the federal handout POTWs still reprint. It pushes source control and regular interceptor cleaning as the way food establishments keep FOG out of the collection system. ^[8] It does not issue you a national pump schedule.

Quarterly is a common city default. It is still too long for a busy fryer line. I have opened tanks at 30 days that were already past 25 percent. I have also seen a sandwich shop go 90 days and look almost empty. The menu decides, not a blog.

If your ordinance lets you petition for a longer interval after a few measured cleanings, do that with photos and depths. Do more than skip a quarter and hope. Missed pumping is how you buy a sewer backup in the dining room.

What permits and paper do you need before you install?

You need the plumbing permit for the work, and you often need a separate FOG or interceptor registration from the sewer authority. On a septic lot you need the onsite-system approval that names the grease trap. Confirm the live forms with those boards. I will not invent a current fee, quota, or processing time.

The drawing should show incoming fixtures, sample tees, venting, traffic rating if a truck can roll over the lid, and the outlet to the sewer or the septic tank. IPC and UPC chapters on interceptors are where reviewers look for those details. ^[3][4] Wisconsin reviewers will also check SPS 382.34 construction notes. ^[10]

Hauler licensing is a second paper path. Many states treat brown grease as septage or as a special non-hazardous waste stream. The person who sucks the tank usually needs a local or state hauler credential. Ask the FOG coordinator for the approved list. If they cannot name who is allowed to pump, you are not ready to sign a cleaning contract.

Keep the approved plan, the inspection card, the FOG permit, and every manifest. GreaseTrapPath sells a $199 one-time Interceptor + Manifest Kit if you want interceptor logs and hauler tickets already laid out. The forms do not replace your city FOG permit and they do not change a statute.

For a longer paper-path walkthrough written for people just entering this work, see Grease trap guide 72 for people starting the paper path and Grease trap guide for people who need the paper path.

Can you clean a grease trap yourself?

Sometimes the indoor unit, almost never the outdoor vault. And never by dumping the contents in a dumpster, a storm drain, or the employee toilet. That last path is how you buy a citation.

A small hydromechanical interceptor can be scooped by kitchen staff in cities that allow owner cleaning, if you have a legal disposal outlet the ordinance names. Plenty of FOG programs still want a licensed hauler even for the indoor box. Confirm that sentence with the board. Do not guess from a neighboring county.

An in-ground gravity interceptor is a different animal. The vault can be a permit-required confined space under OSHA 29 CFR 1910.146 once someone puts a head and shoulders below grade. ^[11] I would not climb in. Hire the hauler. Pay for the vacuum truck. Get the manifest.

Enzyme and bacteria bottles are the product I see sold as a pumping substitute. They are a waste of money if that is the pitch. EPA's food-service FOG materials still center physical removal and kitchen BMPs, not a weekly pour that lets you skip the truck. ^[8] Use a biological additive only if your ordinance allows it and you still pump on measured depth.

DIY "cleaning" that leaves the baffles packed is not cleaning. Open the lid. Look. If you cannot see water surface because of a grease mat, you are late.

What first-year records do inspectors actually ask for?

They ask for the last year of pump-out manifests, the FOG permit or registration, the as-built that matches what is in the ground, and sometimes a simple training log that says dishwashers were told not to put fryer oil down the sink. That is the whole show in most cities.

A usable manifest names the generator, the address, the interceptor size or ID, the gallons pulled, the date, and the hauler's credential. If your city prints its own ticket, use that ticket. If they accept a hauler form, keep a copy on site, not in a truck that left.

I also keep a depth log. Date, inches of FOG, inches of solids, who looked. Massachusetts already requires monthly owner inspections on Title 5 traps. ^[5] Copy that habit even if you are on city sewer. It is the cheapest way to prove you did not ignore the 25 percent line.

Photos help when a new inspector argues the tank is undersized. Photograph the open lid, the inlet tee, and the outlet tee after a cleaning. No drama. Just proof the device exists and is serviceable, which is what the Food Code access rule was driving at. ^[2]

For a first-year binder already sequenced, Grease trap guide 77 for operators who need the paper walks the same file without pretending a national form exists.

What does a grease trap cost in the first year?

I will not invent a national price. Indoor hydromechanical units, outdoor gravity tanks, traffic-rated lids, sample boxes, and pump contracts live in different markets. Anyone quoting one number for the whole country is selling something.

The honest first-year stack is the tank and setting, the plumbing permit, the FOG registration if your POTW has one, the first two or four pump-outs, and any re-inspection after a failed opening. Confirm each line with local quotes and with the board that collects the permit fee. Fees move. I will not freeze a number here that will be wrong next quarter.

Pumping is the line people forget to budget. A quiet cafe and a 200-seat fry line are not the same truck ticket. Get a written interval and a per-visit price from a licensed hauler before you sign the lease. If the hauler will not put the 25 percent rule on the quote, pick another hauler.

State-level cost explainers are where we put the ranges we can actually defend. If you are bidding a site, read grease trap cost in georgia or the California and Florida pages linked above. Use them as a checklist of cost categories, then call local vendors.

Spending extra on a pretty indoor stainless lid while the outdoor tank is still a mystery size is a waste of money. Spend first on the approved volume and on a hauler who shows up.

What happens if you skip the trap or skip the pumping?

The sewer clogs. The floor drain coughs. Wastewater comes back up in the prep sink or the restroom. That is the kitchen version. The city version is a sanitary sewer overflow on the block, followed by a notice of violation under the FOG ordinance.

EPA's collection-system CMOM guidance treats grease blockages as a core operations problem, not a courtesy program. ^[13] The food-service FOG fact sheet exists because food establishments are a known FOG source the pretreatment program expects POTWs to control. ^[8] 40 CFR 403.5 already told the POTW it cannot accept viscous pollutants that cause interference. ^[1] Your missing trap is how the POTW gets in trouble, so the POTW will not be gentle.

Penalties are local. Some cities start with a warning and a forced pumping. Some bill you for the overtime crew that jetted the main. I will not invent a fine table. Read the ordinance PDF the FOG coordinator emails you.

Skipping the trap to "see if they notice" is a bad bet on a new restaurant. Plan reviewers look for the interceptor on the plumbing sheet. Health inspectors look for the accessible lid the Food Code named. ^[2] You will not stealth this.

If grease from your line contributes to a backup in a neighboring space, you also bought a private claim. The paper file is how you show you pumped on time. That is not theory. That is why manifests exist.

How do you confirm local grease trap rules so you skip the national myth?

Call the FOG coordinator and the plumbing plan reviewer. Ask for four files: the ordinance or sewer-use rule, the sizing worksheet, the approved hauler list, and the manifest form. If they cannot send those, you do not yet have a start package.

Then ask three yes-or-no questions. Does the dishwasher tie in? Is owner cleaning of the indoor unit legal? Is the 25 percent rule enforced by measurement or do they also cap the calendar? Write the answers in the job folder with the person's name and the date. Verbal folklore from a contractor is how undersized tanks get buried.

Match the statute family to the site. City sewer in an IPC town means Chapter 10 plus the FOG ordinance. ^[3] California means the California Plumbing Code chapter on traps and interceptors. ^[4] Onsite means the state septic code, and in Massachusetts that is 310 CMR 15.000 with the 1,000 gallon and 36 hour numbers. ^[5] Federal rules still sit underneath as the reason the POTW wrote the ordinance. ^[6][7][9]

There is no national grease trap license, no national quota, and no honest nationwide processing time. Confirm variable facts with the relevant board. Anyone who guarantees approval is not the person who signs the card.

For a start checklist next to the kit, go to /start. GreaseTrapPath is an independent publisher, not a law firm and not a service company. Use this page as a reference even if you never buy a form.

Frequently asked questions

What is grease trap?

A grease trap is a plumbing interceptor that holds kitchen wastewater long enough for fats, oils, and grease to cool and separate. Solids settle, FOG floats, and clearer water leaves to the sewer or septic tank. Indoor steel boxes and outdoor gravity tanks both get called traps in the field. 40 CFR 403.5 is why sewer authorities care.

How do you start grease trap?

Start with the discharge path, then the fixture list, then the local plumbing and FOG reviewers. Size the unit the way that board sizes it, pull the plumbing permit and any interceptor registration, install to the stamped drawing, and keep pump-out manifests. Confirm live fees and forms with the board. There is no national license or national start clock.

Do I need a grease trap if I only run a small sandwich shop?

Maybe. IPC Chapter 10 keys off grease-laden waste in food prep areas, not off your seat count. A shop that only rinses knives may get a waiver. A shop with a grill and a fryer usually will not. Ask the plumbing reviewer and the FOG coordinator in writing. Do not trust a social media list of exempt menus.

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

Trap is the shop word. Interceptor is the code word. Hydromechanical units sit indoors and use baffles plus flow control. Gravity interceptors sit outside and use volume and time. Automatic grease removal devices skim FOG with power. Your plan reviewer picks the type. Winning a vocabulary fight does not pass inspection.

How often should a grease trap be pumped?

When FOG plus settled solids reach about 25 percent of the effective depth, or at the ordinance's calendar cap, whichever comes first. Massachusetts 310 CMR 15.351 requires monthly owner checks and cleaning at 25 percent or every three months on Title 5 traps. Busy fry lines often need a shorter interval than a posted quarterly default.

Can I use enzymes instead of pumping a grease trap?

Not as a substitute. Some ordinances allow additives and still require measured pump-outs. EPA food-service FOG guidance still centers physical removal and kitchen BMPs. If a bottle is sold as a way to skip the truck, it is a waste of money. Confirm additive rules with the FOG board before you pour anything.

Who is allowed to pump a grease trap?

Usually a licensed septage or FOG hauler. Title 5 in Massachusetts names a licensed septage hauler. Many city FOG programs publish an approved list. A few cities let staff scoop a small indoor unit if disposal is legal. Outdoor vaults should stay with the vacuum truck. Confirm credentials with the board that runs the program.

What size grease trap do I need for a restaurant?

Whatever the local sizing method produces for your fixtures, not a national menu chart. On a Massachusetts onsite system, 310 CMR 15.230 sets a 1,000 gallon minimum and 36 hour detention. On city sewer, IPC, UPC, or the FOG worksheet controls. Manufacturer software is a draft. Only the stamped plan is the size.

Do I need a permit to install a grease trap?

Yes, a plumbing permit for the install, and often a separate FOG or interceptor registration from the sewer authority. Onsite lots need the state or county septic approval that names the trap. Confirm the current applications and fees with those boards. Do not treat a contractor invoice as a permit.

What records should I keep for a grease trap?

Keep pump-out manifests, the FOG permit, the approved as-built, inspection cards, and a simple depth log. Massachusetts already wants monthly owner inspections on Title 5 units. A clean file is what you hand an inspector after a backup. Store copies on site, not only in the hauler's truck.

Are grease trap vaults confined spaces?

They can be. Once a person puts a head and shoulders below grade into an in-ground interceptor, OSHA 29 CFR 1910.146 may treat it as a permit-required confined space. I would not climb in. Hire the licensed hauler and stay at grade. Indoor under-sink boxes are a different, shallower job.

What is the 25 percent rule for grease traps?

Pump when the floating grease plus the bottom solids fill 25 percent of the trap's effective depth. Massachusetts wrote that trigger into 310 CMR 15.351, and many city FOG ordinances copied it. Measure with a sludge judge or a similar rod. A calendar quarter is a backup limit, not a reason to ignore a thick mat at day 20.

Does the EPA issue a national grease trap license?

No. EPA writes pretreatment rules such as 40 CFR 403.5 and 403.8 and publishes FOG guidance for POTWs. Your license, if any, is a local FOG registration plus the plumber's and hauler's credentials. There is no federal grease trap operator card and no national quota to reserve.

What happens if grease from my kitchen clogs the sewer?

You can get a local FOG violation, a bill for the jetting crew, a forced pumping, and a private claim if a neighbor floods. EPA CMOM guidance treats grease blockages as a collection-system failure mode. 40 CFR 403.5 already bars viscous pollutants that cause interference. Read your ordinance for the actual penalty ladder.

Sources

1. eCFR 40 CFR 403.5 National pretreatment standards: Prohibited discharges: Solid or viscous pollutants may not be introduced into a POTW in amounts that will cause obstruction resulting in Interference.
2. FDA Food Code 2022, Section 5-402.12 Grease Trap: If used, a grease trap shall be located to be easily accessible for cleaning.
3. ICC International Plumbing Code 2021 Chapter 10 Traps, Interceptors and Separators: IPC Chapter 10 requires grease interceptors or automatic grease removal devices for fixtures with grease-laden waste in food preparation areas.
4. California Plumbing Code 2022 Chapter 10 Traps and Interceptors: California's UPC-based plumbing code places trap and interceptor rules, including grease devices, in Chapter 10.
5. Massachusetts 310 CMR 15.000 Title 5 State Environmental Code: Title 5 requires grease traps for listed kitchen flows, a 1,000 gallon minimum with 36 hour detention and 4 foot depth, plus monthly inspection and cleaning at 25 percent full or every three months.
6. 33 U.S.C. § 1317 Toxic and pretreatment effluent standards: The Clean Water Act authorizes pretreatment standards so pollutants do not pass through or interfere with POTWs.
7. eCFR 40 CFR 403.8 Pretreatment program requirements: Development and implementation by POTW: POTWs with total design flow greater than 5 MGD that receive industrial pollutants which pass through or interfere must establish a pretreatment program.
8. EPA Introduction to the National Pretreatment Program (EPA-833-B-11-001, 2011): EPA's 2011 pretreatment introduction is the federal program manual describing how POTWs implement 40 CFR 403.
9. Wisconsin SPS 382 Design, Construction, Installation, Supervision, Maintenance and Inspection of Plumbing: SPS 382.34 sets Wisconsin plumbing-code rules for interceptors and catch basins, including grease-handling devices.
10. OSHA 29 CFR 1910.146 Permit-required confined spaces: In-ground interceptor vaults can fall under OSHA's permit-required confined space standard when a worker enters below grade.
11. EPA Guide for Evaluating CMOM Programs at Sanitary Sewer Collection Systems: EPA CMOM guidance treats grease blockages as a collection-system operations and overflow problem POTWs must manage.