Grease Trap Regulations in Wisconsin

Overview

Wisconsin food service operators must follow FOG pretreatment rules. The Wisconsin Department of Natural Resources (DNR) and local utilities enforce them. Major utilities include the Milwaukee Metropolitan Sewerage District (MMSD), Madison Water Utility, and Green Bay Metropolitan Sewerage District (NEW Water). Each runs an active FOG program. The goal is to keep fats, oils, and grease out of city sewer systems. The pretreatment framework sits in Wisconsin Administrative Code NR 211. NR 211 sets the oil and grease discharge standards for industrial users and food service kitchens.

Governing Authorities

The Wisconsin Department of Natural Resources (DNR) runs the state's pretreatment program under Wisconsin Administrative Code NR 211. NR 211 covers oil and grease in industrial user effluent. Local enforcement runs through city utilities and sewerage districts with delegated authority.

The Milwaukee Metropolitan Sewerage District (MMSD) provides water reclamation and flood management services. It serves over 1 million people across 29 communities in the Greater Milwaukee Area.

NEW Water (Green Bay Metropolitan Sewerage District) is a wholesale provider of services to 15 city customers. It serves more than 236,000 residents in a 285-square-mile area. It collects and treats an average of 38 million gallons a day.

Madison Water Utility requires food kitchens to submit grease trap upkeep reports each year.

The State of Wisconsin has delegated the Racine Wastewater Utility to act as the local control authority. It permits industries that discharge to the Racine Wastewater Utility.

Key Requirements

All plumbing fixtures in non-dwelling sites where grease, fats, oils, or similar food prep waste enters the drain system must include grease and oil treatment under Wisconsin Administrative Code. Key requirements for Wisconsin food service kitchens include:

• Interceptor Installation: Grease interceptors are required when grease, fats, oils, or similar waste products enter the sanitary drain system in any non-dwelling site.
• Cleaning Frequency: Many cities require grease traps to be cleaned every 90 days. Others let the 25% capacity rule set the schedule. The "25% rule" says that when the trap is 25% full of FOG and solids, it is time to clean it.
• Certified Hauler Use: Food service kitchens must use licensed waste haulers for grease trap pumping and disposal. That ensures FOG waste is handled and disposed of properly.
• Record Retention: Operators must keep 3 years of grease trap cleaning records to prove compliance during inspections. Madison requires food kitchens to submit upkeep reports each year. Reports are due before April 1.
• Best Management Practices: Kitchens must follow Best Management Practices (BMPs) provided by local wastewater utilities. That includes drain screens and proper separation of waste cooking oil.

Fines and Enforcement

Wisconsin utilities enforce FOG rules through inspections and tiered penalties. Specific tools vary by city:

• Madison Tiered Billing System: Failure to submit annual grease trap upkeep reports brings a financial penalty. The kitchen moves to Tier 3 sanitary sewer utility rates. The higher rates match the higher cost of treating stronger sewage. They also push owners to maintain grease traps better.
• General Penalties: Failing to follow grease trap rules can lead to fines from a few hundred to several thousand dollars. Kitchens may face short-term or permanent closure. Severe violations can lead to criminal charges against business owners.
• Sewer Use Violations: Under Racine Municipal Code Section 98-151, no user may discharge wastewater that contains fats, wax, grease, or oils, whether emulsified or not. The same rule covers substances that may solidify between 32°F and normal sewer temperatures.
• Inspection and Compliance: Utilities may inspect grease traps during business hours without prior notice. If a kitchen fails to maintain a grease removal device, the kitchen gets a seven-day notice to do the required upkeep. If it does not comply, the utility may order the work done by an approved contractor at the kitchen's cost.

Major City FOG Programs

Milwaukee

Milwaukee Metropolitan Sewerage District (MMSD) provides water reclamation and flood management services for over 1 million people in 29 communities in the Greater Milwaukee Area. MMSD has a record of 98.6% since 1994 for capturing and cleaning wastewater from those 29 communities across 423 square miles. MMSD enforces FOG rules for food service kitchens across its service area. It works with local health departments on compliance. The district requires proper sizing and upkeep of grease interceptors. It also requires certified hauler paperwork and routine inspections.

Madison

Food kitchens in Madison must submit a grease trap upkeep report each year. Reports are due before April 1. Madison uses a three-tier billing system. Tier 1 is for businesses that take part in organics composting programs. They get slightly lower sewer billing rates. Tier 2 covers most restaurants and food kitchens with grease traps in good standing. Tier 2 owners must submit proof of upkeep at least once a year. New food kitchens start at Tier 2 by default. Madison Metropolitan Sewerage District classifies grease trap waste as non-domestic hauled wastewater. Acceptance by the District is optional. Most grease comes from inside or near the service area.

Green Bay

The City of Green Bay Sanitary Sewer Utility works with the Green Bay Metropolitan Sewerage District (GBMSD or NEW Water). NEW Water treats the sanitary sewage. Fats, oils, and grease can cause blockages, backups, and other issues in the City's sewers. The City runs programs that work with businesses and residents to cut FOG in city sewers. More information about Sanitary Sewer District services and rules sits in Chapter 42, Article II - Sanitary District of the city code.

Racine

The Racine Wastewater Utility has a policy that requires commercial kitchens to follow Best Management Practices to cut FOG discharge. Kitchens must install and maintain grease removal devices (separators, traps, and interceptors) to cut or end the discharge of fats, oils, and greases. Kitchens must clean and service interceptors and traps on a regular schedule. They must follow the Best Management Practices set by the Racine Wastewater Utility. They must keep good up-to-date records of all cleanings, upkeep, and service available during inspections. The State of Wisconsin has delegated the Racine Wastewater Utility to act as the local control authority. It permits industries that discharge to the Racine Wastewater Utility.

Frequently Asked Questions

How often must my grease trap be cleaned in Wisconsin?

Many Wisconsin cities require grease traps to be cleaned every 90 days. Others let the 25% capacity rule set the schedule. The "25% rule" says that when the trap is 25% full of FOG and solids, it is time to clean it. For many restaurants the 25% threshold is reached in about 1 to 3 months of normal use. A common recommendation is to clean commercial grease traps at least every 3 months (quarterly). High-volume kitchens with heavy frying may need monthly cleaning. Smaller kitchens may stretch to a quarterly schedule. Always check with your local utility for the exact rule.

Do I need to use a certified hauler for grease trap pumping?

Yes. Wisconsin food service kitchens must use licensed and certified waste haulers for grease trap pumping and disposal. Certified haulers handle, transport, and dispose of FOG waste at approved facilities. You must keep good up-to-date records of all cleanings, upkeep, and service. Records must be ready during inspections. Many utilities keep lists of certified haulers. Some haulers can submit compliance reports to the utility on your behalf.

What happens if I don't maintain proper records?

In Madison, failure to submit annual grease trap upkeep reports brings a financial penalty. It also moves the billing to Tier 3 sanitary sewer utility rates. Most cities require kitchens to keep 3 years of grease trap cleaning records for compliance checks. Poor records can lead to failed inspections, more monitoring, and fines. In serious cases, enforcement may affect your business. Records should include service dates, hauler info, volume of waste removed, and disposal location.

Find Grease Trap Service in Wisconsin

Looking for grease trap cleaning and upkeep providers in Wisconsin? Our directory lists 10 certified service companies across the state. They know Wisconsin DNR rules and local utility requirements. These pros offer interceptor installation, routine upkeep, emergency pumping, and compliance paperwork. Visit our Wisconsin grease trap service provider directory to connect with haulers and upkeep companies serving your area in 2026.