Last updated 2026-08-21
TL;DR
A grease trap separates fats, oils, and grease from kitchen wastewater before it hits the sewer. Start with your local sewer utility and building department. Ask what type they accept, how they size it, and what pumping records they want. Then have a licensed plumber install a listed unit. Federal rules ban clogging FOG. Local boards set the tank, permit, and pump-out rules. Confirm those before you buy anything.
What is a grease trap?
A grease trap is a tank that slows kitchen wastewater so fats, oils, and grease (FOG) cool and float, and heavier food solids sink, before the water leaves your building. The middle layer goes to the sewer. Cities require that split because FOG hardens in collection lines and helps drive overflows. EPA estimates there are at least 23,000 to 75,000 sanitary sewer overflows a year in the United States, not counting backups into buildings [1].
People use the same phrase for two boxes. A small hydromechanical unit often sits under a three-compartment sink. A large gravity interceptor usually sits outside, buried, with manholes you can open. Codes and utilities often say interceptor for both. The job does not change. Keep FOG out of the pipe.
Federal pretreatment rules do not name your restaurant. They name the clog. 40 CFR 403.5 bans "Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW resulting in Interference" [2]. FOG is that viscous pollutant. Your city sewer ordinance and the adopted plumbing code turn the ban into a tank, a size method, and a pumping schedule.
The FDA Food Code, which many health departments adopt, is blunt about access. "If used, a grease trap shall be located to be easily accessible for cleaning." That is Section 5-402.12 of the 2022 Food Code [4]. Hide a unit under a cabinet you cannot open and you have already failed a health item.
I would not romanticize these tanks. They smell. They need a licensed hauler. In most kitchens that cook, they are required. Cold prep with no fryer can be a maybe. Confirm it. Do not guess from a national blog.
How do you start grease trap?
You start by talking to two offices, not a catalog. Call the local publicly owned treatment works pretreatment contact (the sewer utility). Call the building or plumbing inspector. Ask four things and write the answers with a name and a date. Do we need an interceptor. What listing do you accept (PDI G101, ASME A112.14.3, or a gravity tank under the plumbing code). How do you size it. What pumping log or waste manifest do you want on the wall.
Then hire a licensed plumber who has pulled interceptor permits in that city. Let them file the sizing worksheet and the cut sheets. You do not order a tank first. Wrong flow rating, or a unit the city will not list, is a dead expense. I have seen people do that. It is a waste of money.
Taking over an existing kitchen? Ask for the last two years of pump-out tickets before you sign the lease. An undersized or never-pumped interceptor becomes your problem the day an inspector opens the lid. New construction follows the adopted plumbing code chapter on traps and interceptors, plus any local FOG ordinance [9]. Remodels can be messier. Some cities leave an old tank alone until you change the menu or the fixtures. Confirm that in writing.
Nobody publishes a national processing time for these permits. The board that issues yours is the only clock that matters. Do not treat enzyme bottles as a startup plan. Many sewer ordinances ban additives that push grease downstream. Pumping is the control that actually shows up on a manifest.
Do you even need a grease trap for your kitchen?
If you cook, fry, grill, or run a dishwasher on food-service wastewater, the honest default is yes. Many POTWs require grease interceptors at food service establishments for that reason [3]. A bakery with butter and pans usually needs one. A bar with a fryer needs one. A hospital kitchen needs one. The trigger is FOG in the drain, not your tax category.
A coffee counter with sealed drinks and no food prep is often a no. A jewelry store with a break-room sink is a no. A sandwich shop that only assembles cold product can go either way. The sewer utility decides, not the equipment seller. Ask them before you spend.
Health departments and sewer departments do not always agree on the same kitchen. The health inspector wants access and sanitation under the Food Code [4]. The pretreatment coordinator wants less FOG at the plant under 40 CFR 403 [2] [5]. You need both answers. One verbal "you're probably fine" is not a file.
If a landlord says the building already has a shared interceptor, get the size, the last pump date, and who pays the hauler. Shared tanks fail when every tenant assumes someone else is pumping. I would not open on a handshake about a buried tank I have not seen.
Menu changes restart the question. Add a wok line or a smoker and the old under-sink unit may be illegal the next inspection. Confirm with the same two offices you called at the start.
What is the difference between a grease trap and a grease interceptor?
In the field, grease trap usually means the small indoor unit. Grease interceptor usually means the big outdoor tank. Manufacturers and codes mix the words. Hydromechanical grease interceptors (HGIs) are rated in gallons per minute, often in the 10 to 50 gpm catalog range, and they use baffles plus a flow-control device. Gravity grease interceptors (GGIs) are rated in gallons of volume, often hundreds to a few thousand gallons, and they rely on detention time.
Your city may ban indoor HGIs for certain menus. Your city may require a GGI once seating or fixture units cross a local line. Florida's plumbing code puts traps, interceptors, and separators in Chapter 10, and local amendments pile on [9]. Wisconsin's SPS 382.34 is the state plumbing rule that tells you when an interceptor is required for grease and other harmful wastes [11]. Read the local adoption, not a national sales sheet.
I prefer an outdoor gravity tank when the lot can take it and the menu is heavy. It is uglier. It is easier to pump without shutting the dish line. Indoor units make sense in tight urban spaces if the utility accepts them and you can actually open the lid [4] [6].
| Type | Where it usually sits | How it is rated | What I use it for |
|---|---|---|---|
| Hydromechanical (HGI) | Indoors, often under a sink | Flow, commonly about 10 to 50 gpm in catalogs | Small prep, tight rooms, if the city lists it |
| Gravity (GGI) | Outside, buried, with manholes | Volume, often 500 gallons and up | High FOG menus, easier pumping |
| Shared building tank | Basement or alley | Whatever the last plumber installed | Only if you have tickets and a written share rule |
If a salesperson says one model fits every kitchen, hang up.
Who regulates grease traps and what rules actually apply?
Three layers stack. Federal pretreatment rules set the floor. 40 CFR Part 403 tells POTWs to keep users from sending pollutants that interfere with treatment or pass through the plant [5]. 40 CFR 403.5 lists specific prohibitions, including viscous pollutants that obstruct flow, and it sets a pH floor of 5.0 unless the plant is designed for lower [2]. That is why your fryer drain is a sewer issue more than a plumbing issue.
The second layer is the local sewer ordinance and the POTW's FOG program. New York City's Department of Environmental Protection publishes grease interceptor rules for food service [6]. Texas Commission on Environmental Quality posts FOG guidance for cities that run pretreatment [7]. Massachusetts keeps a public FOG page for communities and kitchens [8]. California's statewide sanitary sewer systems order (WQ 2022-0103-DWQ) requires sewer agencies to control FOG when it contributes to spills [10]. Those are different papers. They all point at the same grease.
The third layer is plumbing and health. The adopted plumbing code sizes and locates the tank [9] [11]. The health department checks whether you can clean it [4]. EPA's food-service FOG fact sheet is the national explainer many cities still hand out [3].
There is no single federal grease-trap license for a restaurant. There is a local permit, a local size method, and a local pumping rule. Confirm with the relevant board. I would not trust a franchise packet that quotes one city's ordinance as if it were national law.
How do you size a grease trap the first time?
You do not size it from a blog. You size it with the method your adopted code and your POTW both accept. Common methods are drainage fixture units on the connected sinks, a flow-rate calculation for hydromechanical units, or a seating and meals formula for gravity tanks. Florida Plumbing Code Chapter 10 is one state's version of that chapter [9]. Wisconsin SPS 382.34 is another [11]. Cities rewrite the numbers.
I would not pick a 20 gpm under-sink unit because it fits the cabinet. Flow rating has to match the peak discharge of the fixtures that actually tie in. A dishwasher surge will blow FOG through an undersized HGI. An oversized outdoor tank you did not need wastes excavation money. Both errors show up later as tickets or as a second install.
Ask the plumber for the worksheet, the fixture list, and the listing (PDI or ASME for HGIs). Keep that packet. Inspectors ask for it years later. If two methods disagree, use the one the pretreatment office names in writing. Their letter beats a manufacturer app.
Existing tanks get a different question. Is this size still legal for this menu. If the last operator ran salads and you are adding fried chicken, the old volume may fail the 25 percent solids-and-grease rule on a short cycle [3]. Measure the tank. Do not trust the lid stamp if the vault was replaced.
State cost pages help you think about hardware and hauling later, not about gallons today. See Grease trap cost in California and Grease trap cost in Alabama after you have a size, not before.
What permits and paper do you need before install?
Most installs need a plumbing permit. Many cities also want a FOG registration or an industrial-waste permit for the kitchen. NYC DEP treats interceptor installation and maintenance as a sewer-protection duty, not a suggestion [6]. Other utilities bury the same duty in a pretreatment packet [3] [5] [7].
Paper that actually matters on day one: the permit application, the site plan showing the tank and the sample point if they want one, the manufacturer's listing sheet, the plumber's license, and later the hauler's first manifest. Health may want to see access clearances under Food Code 5-402.12 [4]. I keep that stack in one folder, not in a text thread.
Fees are local and they change. I will not invent a current fee, quota, or processing time. Confirm the dollar amount and the clock with the board that issues the permit. Some building departments post a fee schedule. Some pretreatment offices invoice after inspection. If a website looks a year stale, call.
Do not start excavation on a verbal. Get the approved drawing back. Outdoor tanks hit other rules (traffic lids, setbacks, sometimes stormwater). Indoor units hit fire and accessibility rules. The plumber should know the local stack. If they do not, hire someone who pulled an interceptor permit on your block last year.
Renewal is a different paper path than first install. If you already operate, read grease trap renewal in california or grease trap renewal in florida for the state-shaped version of that chore. First-year operators still start with the install permit, not the renewal form.
How often do you pump a grease trap?
As often as your ordinance says, or sooner if FOG plus settled solids hit the local depth limit. Many municipalities require a full pump-out about every 90 days, or when 25 percent of the interceptor depth is grease and solids, whichever comes first [3]. That 25 percent rule is the one inspectors can check with a sludge judge in two minutes.
Heavy fryer volume will beat 90 days. A pancake house on a weekend tourist street may need monthly service. A low-FOG cafe may stretch if the city allows a longer interval after you prove it with measurements. I would not stretch on a guess. Measure. Log the inches.
Pumping means a complete evacuation, not skimming the top and leaving the sludge. Incomplete pump-outs are how you fail the next 25 percent check the same month. Use a hauler the POTW recognizes. Ask for a printed ticket with date, gallons, truck ID, and disposal site. That ticket is your defense.
Lids have to open. FDA Food Code 5-402.12 exists because inspectors and pumpers cannot service a trap they cannot reach [4]. Do not park a freezer on the indoor lid. Do not pave over an outdoor manhole. Both happen. Both are expensive.
Additives are not a pump-out. Some products shift grease downstream, which is the interference 40 CFR 403.5 already bans [2]. If your ordinance is silent, still ask pretreatment before you pour anything in. I skip additives. Pumping is cheaper than a blockage claim.
What records should you keep in year one?
Keep every pump-out ticket, every inspector note, the approved sizing worksheet, the cut sheet, and a simple log with date, gallons, hauler name, and who was on site. If your city issues a FOG permit number, write it on the folder. If they want a waste manifest form, use theirs, not a napkin.
Year one is when you learn the real interval. If solids hit 25 percent at day 50, your 90-day calendar is fiction [3]. Adjust the hauler contract. Keep the measurement notes. Pretreatment staff like numbers more than stories.
Train one person to meet the pumper. Someone has to open the lid, watch that the tank is emptied, and refuse a skim job. Put that name on the log. When that person quits, retrain the next day. Grease programs fail on staff turnover more than on tank brand.
Want a paper checklist already laid out? GreaseTrapPath sells a $199 one-time Interceptor + Manifest Kit. A bound notebook and the hauler's tickets can do the same job if you actually fill them in. The folder is the point. Not the brand of folder.
Scan the tickets. Paper melts in a dish room. When you later need grease trap renewal in alabama or grease trap renewal in arizona, those scans are the file the board asks for. No approval or timing guarantee comes from a tidy binder. It only keeps you from inventing history at the counter.
What does a first-year grease trap actually cost?
First year is hardware, plumber, local permit, and pumping. Hardware swings with type. An indoor HGI is a different invoice than a buried 1,000-gallon gravity tank with traffic lids. Labor swings with access, groundwater, and whether you are cutting a new slab. I will not invent a national price. Anyone who quotes one number for the whole country is selling.
Permit fees are set by the city or county that stamps the job. Confirm the current fee with that board. Do not use last year's PDF if they say the schedule changed. Pumping is a recurring line. Quarterly service is common where the 90-day rule applies [3]. Heavy menus cost more because the truck comes more often.
Some POTWs also levy FOG surcharges or extra sampling if you are a significant industrial user under the pretreatment program [5]. Most small restaurants are not SIUs. Some still pay a commercial FOG fee. Ask. It belongs in the year-one budget even if the dollar amount is local.
For state-shaped dollar talk, use pages that stay honest about ranges and tell you to confirm. Grease trap cost in Arizona and Grease trap cost in Arkansas are that kind of next click. They will not replace a plumber's bid on your site.
What I would not buy in year one: enzyme subscriptions, miracle inserts with no listing, or a second spare tank as backup. Spend on access, a correct listing, and a hauler who shows up.
What mistakes waste money on grease traps?
Buying the tank before the utility names the type. That is the expensive one. Cities reject unlisted HGIs and undersized gravity vaults every week. Return freight on a concrete interceptor is not a plan.
The second waste is hiding the lid. Food Code 5-402.12 is not decoration [4]. If the pumper cannot open it, you pay a second trip or you fail the inspection. Leave clear space. Teach the night crew that the lid is not storage.
The third waste is treating additives as maintenance. 40 CFR 403.5 already cares about what leaves your building [2]. If the product only moves FOG to the city main, you bought a future blockage with your own money. Pump. Measure. Log.
Skipping manifests is how a cheap year becomes a fine year. EPA's FOG fact sheet exists because food-service grease is a collection-system problem, not a myth [3]. Your ticket file is how you show you are not that problem. No tickets, no story.
I also see people overbuild. A huge outdoor tank on a low-FOG menu wastes excavation and then goes septic between rare pump-outs. Match the code method [9] [11]. Do not let a salesperson upsell volume you cannot defend on the worksheet.
Lease language is a quiet waste. If the landlord owns the interceptor and you own the violations, you will pay twice. Put pumping duty and access in the lease. Get the last tickets. Walk away if they cannot produce them.
Where do you confirm local rules before you buy anything?
Call the POTW pretreatment desk and the building department. Those two. Then the health department if they inspect grease access. Ask for the FOG ordinance, the accepted listings, the sizing method, the pump interval, and the manifest form. Write names. Keep emails.
State pages help you find the right desk. TCEQ's FOG page is a door into Texas city programs [7]. Massachusetts publishes a FOG overview for communities [8]. California sewer agencies live under WQ 2022-0103-DWQ when spills and FOG mix [10]. NYC DEP states interceptor duties in public language [6]. None of those pages issues your permit. They tell you who does.
Federal text is short and worth reading once. 40 CFR 403.5 is the prohibition list [2]. EPA's pretreatment introduction explains why your city has a FOG program at all [5]. EPA's food-service fact sheet is the plain explainer staff still quote [3]. The 2022 FDA Food Code Section 5-402.12 is the access line health will recite [4].
GreaseTrapPath is an independent publisher, not a law firm and not a service company. This page is a reference. If you want the kit and a start path after you have talked to your board, see /start. No approval promise lives there either.
Confirm variable facts with the relevant board. Rules move. Fee schedules move. I would not pour concrete on a printed guide, including this one, without that call.
Frequently asked questions
What is grease trap?
A grease trap is a tank that slows kitchen wastewater so fats, oils, and grease float and food solids sink before water enters the sewer. Small indoor units and large outdoor interceptors do the same job. Cities require them because FOG helps clog mains. EPA estimates 23,000 to 75,000 sanitary sewer overflows a year in the United States.
How do you start grease trap?
Call the sewer utility pretreatment desk and the building department first. Ask if you need an interceptor, what listing they accept, how they size it, and what pumping log they want. Then hire a licensed plumber to file cut sheets and install. Do not buy a tank first. Confirm fees and timing with that board. There is no national processing clock.
Is a grease trap the same thing as a grease interceptor?
Field talk often uses trap for a small indoor hydromechanical unit and interceptor for a buried gravity tank. Codes mix the words. Both separate FOG from wastewater. Your city decides which type is legal for your menu and fixtures. Ask pretreatment and the plumbing inspector before you order either box.
Do I need a grease trap if I only do light food prep?
Maybe. Cooking, frying, and dishwashing usually trigger a local FOG rule. A sealed-drink coffee counter often does not. A cold sandwich line can go either way. The POTW decides, not a national article. Get the answer in writing before you skip the tank or before you buy one you cannot return.
How often should a grease trap be pumped?
Follow your ordinance. Many cities want a full pump-out every 90 days or when grease plus solids fill 25 percent of the tank depth, whichever comes first. Heavy fryer menus beat 90 days. Measure with a sludge judge and keep tickets. Incomplete skim jobs fail the next 25 percent check.
Can I use enzymes or bacteria instead of pumping?
I would not. Many sewer ordinances ban additives that push FOG downstream. Federal pretreatment rules already prohibit viscous pollutants that obstruct the POTW. Pumping and a written manifest are the controls inspectors recognize. Ask pretreatment before you pour anything in. Most kitchens should skip the bottles.
Who is allowed to haul grease trap waste?
A hauler your city or county recognizes, often with a local license and a legal disposal site. Ask the POTW for the list if they keep one. Get a ticket with date, gallons, truck ID, and destination. That paper is your year-one defense. Do not let an unlicensed truck "take it somewhere."
What size grease trap do I need?
The size comes from the method your adopted plumbing code and your POTW both accept. That may be fixture units, flow rate for a hydromechanical unit, or a seating and meals formula for a gravity tank. I would not pick a cabinet-friendly gpm number myself. Have the plumber submit the worksheet the city uses.
Do I need a permit to install a grease trap?
Usually a plumbing permit, and in many cities a FOG or industrial-waste registration too. Health may check access. Fees and wait times are local. Confirm both with the issuing board. Do not excavate on a verbal. Keep the approved drawing, the listing sheet, and the first hauler ticket in one folder.
What happens if I skip grease trap pumping?
The tank hits the 25 percent rule, FOG leaves for the city main, and you own the inspection and the blockage risk. EPA treats FOG as a collection-system problem. Local programs can fine, require more pumping, or shut a line. You also lose the ticket history boards ask for at renewal.
Are under-sink grease traps legal?
Sometimes. Many cities accept listed hydromechanical units for smaller kitchens if the lid is easy to open and the flow rating matches the fixtures. Some menus or fixture counts force an outdoor gravity tank. FDA Food Code 5-402.12 still requires access for cleaning if a trap is used. Confirm the type before you buy.
How long does grease trap approval take?
There is no honest national number. Plumbing and FOG desks set their own clocks, and those clocks change. Anyone publishing a guaranteed turnaround is inventing it. Ask the board that will stamp your job for the current queue. Plan the install date after you have the approved drawing, not before.
What is a FOG manifest and do I need one?
It is the haul ticket that shows when the interceptor was pumped, how many gallons left, who hauled it, and where it went. Many POTWs want that form on site. Year one, keep every ticket and a simple log. If your city has its own blank, use that blank. A notebook works if you actually fill it in.
Can I install a grease trap myself?
I would not. Most cities require a licensed plumber and a permit. Outdoor tanks also hit excavation, lid, and sometimes traffic-load rules. A bad invert or a missing flow control fails inspection and wastes the hardware. Hire someone who has pulled interceptor permits on your block and keep their worksheet.
Sources
- U.S. EPA, Sanitary Sewer Overflows (SSOs): EPA estimates at least 23,000 to 75,000 sanitary sewer overflows per year in the United States, not including backups into buildings.
- 40 CFR 403.5 National pretreatment standards: Prohibited discharges: Federal rules prohibit solid or viscous pollutants that obstruct POTW flow and, unless the plant is designed for it, discharges with pH lower than 5.0.
- U.S. FDA Food Code 2022, Section 5-402.12 Grease Trap: If used, a grease trap shall be located to be easily accessible for cleaning.
- U.S. EPA, Introduction to the National Pretreatment Program (2011): The National Pretreatment Program requires POTWs to control industrial and commercial discharges that can interfere with treatment works.
- Texas Commission on Environmental Quality, Fats, Oils, and Grease (FOG): TCEQ publishes FOG assistance for local pretreatment programs and food-service grease control.
- Commonwealth of Massachusetts, Fats, oils and grease (FOG): Massachusetts maintains public FOG guidance for communities and kitchens that discharge to sewers.
- Florida Plumbing Code 2023, Chapter 10 Traps, Interceptors and Separators: Florida's adopted plumbing code regulates traps, interceptors, and separators, including grease interceptors.
- California State Water Resources Control Board, WQ 2022-0103-DWQ Statewide General WDR for Sanitary Sewer Systems: California's statewide sanitary sewer systems order requires enrollees to address FOG when it contributes to sewer spills.