Grease Trap Requirements
Madison, WI

FOG Compliance in Madison, WI

Food service establishments in Madison operate under a combination of federal EPA pretreatment standards, Wisconsin 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.

Pumping frequency is the compliance rule restaurant owners interact with most often. In Madison, the rule is: Regular pumping required. This is more lenient than the US median, typical of jurisdictions with lower-volume food service sectors. 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 Madison 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: Per Wisconsin Plumbing Code requirements.

Madison requires a dedicated FOG permit for any food service establishment generating fats, oils, and grease. The annual permit fee is Contact Building Inspection Plumbing Dept at 608-266-4346. The permit is separate from, and in addition to, the plumbing permit required at installation. Violations carry maximum penalties of Per Madison Code of Ordinances enforcement provisions . 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.

Madison 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 proof of maintenance required; periodic city inspections. 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 City of Madison Engineering Dept; Madison Metropolitan Sewerage District (MMSD), 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.