Grease Trap Requirements
Detroit, MI

FOG Compliance in Detroit, MI

Food service establishments in Detroit operate under a combination of federal EPA pretreatment standards, Michigan state plumbing code, and city-level FOG ordinances. Together these rules determine how grease traps must be sized, how often they must be pumped, and what happens when a restaurant falls out of compliance. The city has approximately 3,509 food service establishments — every one of them subject to the rules summarized below.

Pumping frequency is the compliance rule restaurant owners interact with most often. In Detroit, the rule is: Every 90 days minimum or more frequently as needed to maintain proper operation. This aligns with the 90-day US median enforced by most major cities. The city follows the Uniform Plumbing Code (UPC) for trap sizing and installation. Under Section 1014, which applies a fixture drainage load formula with a retention time factor, grease interceptors installed in Detroit must meet minimum capacity thresholds based on the fixtures connected to them — 3-compartment sinks, dishwashers, pre-rinse stations, wok stoves, and floor drains on the cook line. The local minimum trap size is: 1,000 gallons minimum for gravity grease interceptors per Michigan Plumbing Code; smaller hydromechanical units as permitted by code for lower-volume establishments.

Detroit requires a dedicated FOG permit for any food service establishment generating fats, oils, and grease. The annual permit fee is No separate published FOG permit fee; covered under DWSD industrial pretreatment permit. The permit is separate from, and in addition to, the plumbing permit required at installation. Violations carry maximum penalties of $10,000 per violation per day; subject to surcharges and cost recovery , in line with typical US municipal penalties. Fines typically escalate with repeat violations, and severe discharges that cause sanitary sewer overflows can trigger federal Clean Water Act penalties layered on top of local fines.

Detroit enforces the 25 percent rule: grease traps must be pumped before the combined FOG and settled solids reach 25 percent of the trap's total liquid depth. Inspectors measure the depth with a sludge judge or dipstick, typically at surprise visits. Exceeding the threshold at inspection triggers a notice of violation and mandatory emergency pump-out, regardless of the scheduled pumping cycle. Annual inspections; DWSD may inspect more frequently for problem facilities. Establishments must maintain pumping logs, hauler manifests, and inspection reports on-site — missing records is itself a violation in most enforcement actions. Enforcement authority rests with the Detroit Water and Sewerage Department (DWSD) - Industrial Pretreatment Program, which handles permit issuance, inspections, and hauler licensing.

For a deeper explanation of the rules this city enforces, read our guides on how grease traps work and the 25/50 pumping rule.