If your business cooks, prepares, or washes dishes on site, grease trap requirements apply to you: you must install an approved, properly sized grease interceptor before opening, keep it below 25% grease and solids by depth through regular pump-outs, retain service records for at least three years, and pass unannounced inspections by your local wastewater authority. The rules come from your city or utility, but they are backed by the federal pretreatment program under the Clean Water Act, and civil penalties start at $1,000 per day per violation.1eCFR. 40 CFR 403.8 – POTW Pretreatment Program Requirements
Which Food Businesses Are Covered
Restaurants generate the most fats, oils, and grease (FOG), but the requirement reaches much further. School cafeterias, hospital kitchens, hotel food service, catering commissaries, food trucks operating from shared prep kitchens, convenience stores with hot food programs, and food manufacturing facilities all fall under local FOG ordinances. Even a coffee shop that only washes dishes and serving equipment on site may need a small under-sink unit, because residual grease from plates and cookware still enters the drain.
There is one consistent exemption: facilities selling only pre-packaged food with no on-site preparation or dishwashing. A vending machine room does not need a grease trap. Anything involving heating, frying, grilling, baking, or dishwashing does.
Sizing, Materials, and Installation
Grease control equipment falls into two categories. Hydromechanical grease interceptors are smaller units installed indoors, often under a sink or on the kitchen floor. Gravity grease interceptors are larger tanks buried outside the building. Your local authority decides which is acceptable for your operation, and a licensed plumber or engineer typically has to perform the sizing calculation and submit it with the permit application.
Most jurisdictions use one of two sizing methods. Under the International Plumbing Code, hydromechanical units are rated by flow-through in gallons per minute, with each rate tied to a required grease retention capacity in pounds — a 20 GPM unit, for example, must retain at least 40 pounds of grease. Gravity interceptors are sized by multiplying peak drain flow in gallons per minute by a 30-minute retention time.2ICC. International Plumbing Code 2024 – Chapter 10 Traps, Interceptors and Separators The Uniform Plumbing Code uses a different approach based on meals per peak hour, waste flow rate, retention time, and a storage factor.
Traps must be built from materials that resist the acidic conditions created by decomposing FOG. Cast iron, stainless steel, and high-density polyethylene are the three standard options. Cast iron is common indoors for its fire resistance; polyethylene dominates outdoor installations because it holds up in soil and is easier to handle during placement.
Hydromechanical interceptors also need a vented flow control device installed upstream to regulate flow to the unit’s certified rate. Without it, peak-hour surges push water through faster than the interceptor can separate grease. Many jurisdictions further require a downstream sampling port where inspectors can collect effluent for testing.
Permits and Cost
You need a plumbing permit before installation. The application typically requires the manufacturer’s specification sheet, a site plan showing the interceptor and connected fixtures, the peak flow calculation, and the unit’s model number. Permit fees commonly run from a few hundred dollars to over a thousand for complex projects.
Equipment and installation vary widely. A small under-sink hydromechanical unit runs a few thousand dollars installed. A standard 1,000-gallon outdoor gravity interceptor typically costs $12,000 to $35,000 once excavation, plumbing connections, and labor are included. High-volume operations can exceed $50,000. These are non-negotiable upfront costs; a food service business cannot legally open without an approved system in place.
The 25% Rule and Pump-Out Frequency
The central maintenance standard is the 25% rule. The combined depth of floating grease and settled solids at the bottom of the trap cannot exceed one-quarter of the total liquid depth. Past that threshold, the trap loses its ability to separate grease from water and untreated FOG flows straight into the sewer. Inspectors treat a trap over 25% the same way they treat a broken or bypassed one.
Gravity interceptors generally must be fully pumped at least every 90 days. Smaller hydromechanical units usually need service weekly or biweekly in busy kitchens with fryers and griddles. These intervals are floors, not targets. If your trap hits 25% before the scheduled pump-out, you are already out of compliance regardless of when it was last cleaned.
Some municipalities allow variances that extend the pump-out interval, but approval is not automatic. You typically need a clean compliance history over several consecutive pump cycles, effluent testing showing grease levels well below discharge limits, and evidence the interceptor is in good working condition. Variances tie to the specific business and location, do not transfer with ownership, and expire with the permit cycle.
Professional pump-out costs depend on trap size and regional pricing. Small indoor units typically run $115 to $250 per service. Mid-size floor-mounted traps cost roughly $200 to $450. Large outdoor interceptors range from $350 to $750, and emergency service on a neglected trap can exceed $1,000. Northeast and West Coast markets tend to run 20 to 40% above Midwest and Southeast averages.
What You Cannot Put Down the Drain
Federal regulations at 40 CFR 403.5 set a baseline of substances that cannot enter any public sewer system, regardless of local rules. Prohibited discharges include materials creating fire or explosion hazards (flashpoint below 140°F), corrosive substances with a pH below 5.0, solid or viscous materials in quantities that obstruct sewer flow, and heat that would raise the treatment plant temperature above 104°F.3eCFR. 40 CFR 403.5 – National Pretreatment Standards: Prohibited Discharges Petroleum-based oils and products of mineral oil origin are banned in interference-causing amounts.
For kitchens, the most relevant prohibition is on solid or viscous pollutants that cause obstruction. Grease qualifies: it enters drains as a liquid, then solidifies inside pipes.
Chemicals, Enzymes, and Bacteria in the Trap
Many municipalities specifically prohibit pouring chemicals, enzymes, or bacterial products into a grease trap. Solvents and caustic cleaners dissolve the grease inside the trap, but the grease does not disappear; it flows out in liquid form and re-solidifies downstream in the sewer main. Enzymes work the same way. Bacterial treatments face a different problem: kitchen conditions are too volatile in temperature, pH, and flow for bacteria colonies to survive consistently.
Some jurisdictions allow biological treatments under strict conditions, generally requiring laboratory proof of complete digestion without increasing downstream grease volume and pre-approval from the local authority. The safe assumption is that anything added to your trap beyond normal kitchen wastewater needs explicit written approval first.
Records You Must Keep
Documentation is a legal requirement, not just good practice. Under 40 CFR 403.12, users subject to pretreatment reporting must retain monitoring records for at least three years, and that period extends during unresolved litigation or on request from a regulatory authority.4GovInfo. 40 CFR 403.12 – Reporting Requirements for POTWs and Industrial Users
Every pump-out generates a haulage manifest from the service provider, documenting chain of custody from your kitchen to the disposal site. The EPA’s model manifest includes fields for the hauling company’s permit number, the volume of waste removed in gallons, and the authorized disposal location.5Environmental Protection Agency. Model Hauled Waste Manifest The manifest exists to prevent illegal dumping; if your hauler dumps into a storm drain instead of a licensed facility, its presence or absence determines where liability falls.
Beyond manifests, you need an on-site log recording the date and time of each service, the grease depth measured before pump-out, and the technician’s signature. Logs must stay on the premises and be available during business hours. Inspectors cross-reference log entries against manifests to verify that service intervals were met. A missing manifest or incomplete log entry is treated as a violation of the pretreatment ordinance, in the same category as physical failure of the trap.
Inspections and Penalties
Local pretreatment programs must have authority to inspect, conduct surveillance, and monitor independent of information the business provides.1eCFR. 40 CFR 403.8 – POTW Pretreatment Program Requirements A pretreatment coordinator or health inspector can arrive without notice during business hours, request access to your trap, measure grease and solids, and review documentation on the spot.
The visit has two parts. First, the physical check: the inspector opens the trap, measures the grease cap and settled solids against the 25% threshold, and looks for damage, bypass plumbing, or improper modifications. Second, the paperwork review: your maintenance log against the haulage manifests. If both pass, you receive a notice of compliance. If not, the inspector issues a corrective action report with a resolution timeline, typically requiring a follow-up visit within 10 to 30 days.
Federal rules require local programs to have authority to seek civil or criminal penalties of at least $1,000 per day per violation, and many local ordinances go higher. Authorities can also seek injunctive relief and can immediately halt a discharge presenting an imminent threat to public health or the sewer system. Continued non-compliance can lead to suspension of a business license or disconnection from the sewer, which effectively closes the kitchen. Some municipalities also impose surcharges on wastewater exceeding biological oxygen demand or suspended solids limits, so a poorly maintained trap generates ongoing utility costs on top of any fine.
Practices That Keep the Trap Working
Reducing the FOG that reaches the trap is the cheapest way to stay compliant. Every jurisdiction expects food service businesses to follow best management practices, and many require documented staff training.
Dry wiping is the single most effective practice. Before any pot, pan, or plate goes into the sink or dishwasher, staff should scrape food waste into the trash and wipe residual grease with paper towels. The EPA’s FOG compliance workbook recommends rubber scrapers on cookware and absorbent paper under fryer baskets to catch drips.6Environmental Protection Agency. Fats Oil and Grease Compliance and Best Management Practices “No Grease Down the Drain” signs above sinks serve as a constant reminder.
Yellow Grease vs. Brown Grease
Used fryer oil, called yellow grease in the industry, should never go down a drain. It is recyclable and often has economic value. Rendering companies will pick it up for free or pay for it, converting it to biodiesel or animal feed ingredients. Store it in a designated outdoor grease recycling bin, separate from your trap waste. Brown grease is the contaminated material accumulating inside your trap, a mixture of water, food particles, and degraded fats that must be pumped by a licensed hauler and disposed of at an authorized facility. Mixing the two destroys the value of the yellow grease and can create compliance problems.
Staff Training
Many local programs require FOG training at least twice per calendar year. Training should cover dry-wiping procedures, disposal of cooking oil, spill cleanup, and the consequences of a failed inspection. Attendance records and employee signatures matter: inspectors check for training documentation, and missing logs can be cited as a violation on their own. Designating a specific person each shift as responsible for FOG management helps ensure the practices actually happen when the kitchen gets busy.