Grease Trap Requirements
Naperville, IL

FOG Compliance in Naperville, IL

Food service establishments in Naperville operate under a combination of federal EPA pretreatment standards, Illinois 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 Naperville, the rule is: Regular cleaning per manufacturer specifications and city requirements. This aligns with the 90-day US median enforced by most major cities. The city follows the International Plumbing Code (IPC) for trap sizing and installation. Under Section 1003.3.4, which sizes traps by drainage fixture unit counts, grease interceptors installed in Naperville 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 Illinois Plumbing Code (77 IL Admin Code 890) and city requirements.

Naperville requires a dedicated FOG permit for any food service establishment generating fats, oils, and grease. The annual permit fee is Unknown - contact City of Naperville Building Department; DuPage County inspection fee $150. The permit is separate from, and in addition to, the plumbing permit required at installation. Violations carry maximum penalties of Unknown - per city sewer use ordinance 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.

Naperville 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. Periodic per city/DuPage County oversight. 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 Naperville Public Works / DuPage County Public Works, 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.