Grease Trap Requirements
Milwaukee, WI

FOG Compliance in Milwaukee, WI

Food service establishments in Milwaukee 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. The city has approximately 2,122 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 Milwaukee, the rule is: Every 90 days minimum. 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 Milwaukee 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: 750 gallons minimum for gravity grease interceptors; hydromechanical units sized per Wisconsin Plumbing Code SPS 382 fixture unit tables (minimum 20 GPM).

Milwaukee requires a dedicated FOG permit for any food service establishment generating fats, oils, and grease. The annual permit fee is No separate published annual FOG permit fee; plumbing permit required for interceptor installation; MMSD sewer use charges apply. The permit is separate from, and in addition to, the plumbing permit required at installation. Violations carry maximum penalties of $5,000 per violation per day under city sewer use ordinance; MMSD may assess surcharges for non-compliance , 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.

Milwaukee 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 by MMSD or city inspectors; complaint-driven inspections also conducted. 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 Milwaukee Metropolitan Sewerage District (MMSD); City of Milwaukee Department of Neighborhood Services (plumbing permits), 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.