Grease Trap Regulations in Iowa

Overview of Iowa FOG Compliance Framework

Iowa food service owners operate under a layered system for managing fats, oils, and grease (FOG). Federal pretreatment rules under 40 CFR Part 403 require local Publicly Owned Treatment Works (POTWs) to monitor indirect dischargers — including restaurants — that send wastewater into municipal sewers. The Iowa Department of Natural Resources (DNR) issues NPDES permits to wastewater plants and sets the state-level annual fee structure for wastewater oversight.

Day-to-day FOG enforcement in Iowa happens at the city level. Each city writes its own sewer use ordinance. Each city sets its own pumping schedule and its own fine amounts. Restaurants in Des Moines, Sioux City, Cedar Rapids, Davenport, and Iowa City each face different rules. Every program traces back to the same federal authority. The sections below cover the verified federal and local requirements. Contact your local Authority Having Jurisdiction (AHJ) for specifics.

Governing Authorities

The federal backbone is the EPA National Pretreatment Program. Under 40 CFR §403.5(b)(3), no industrial user may discharge solid or viscous pollutants that obstruct a POTW. That rule backs every grease interceptor mandate in Iowa. POTWs that have seen interference or pass-through must set local limits under 40 CFR §403.5(c). EPA Region 7 in Lenexa, Kansas, oversees Iowa's federal compliance.

At the state level, the Iowa DNR runs the NPDES program for direct discharges to surface waters. The DNR charges annual fees to fund wastewater oversight. Major municipal facilities pay $1,275 per year. Minor municipal facilities pay $210 per year. Minor industrial facilities pay $300 per year. Semipublic facilities pay $340 per year (Iowa Admin. Code 567-60.14). Individual restaurant FOG enforcement is delegated to the local POTW.

The main municipal authorities Iowa owners deal with include:

• Des Moines Metropolitan Wastewater Reclamation Authority (WRA) runs a regional FOG ordinance adopted by WRA member cities in 2006. The program covers more than 2,000 food service businesses across the metro area (Des Moines WRA FOG Program).
• Sioux City Wastewater Treatment Division enforces a FOG ordinance with different pumping rules for indoor traps and outdoor interceptors (Sioux City FOG FAQs).
• City of Davenport, Water Pollution Control enforces sewer discharge rules under the Davenport Sewer Ordinance, including required notice for accidental discharges (Davenport Sewer Ordinance §13.16.200).
• City of Cedar Rapids Building Services handles permitting for new interceptor installations (Cedar Rapids Building & Trades Fees).
• Iowa City Public Works runs a 9.66 million-gallon-per-day wastewater plant and maintains about 300 miles of sanitary sewer piping. FOG controls are managed through the city's wastewater utility (Iowa City Public Works).

Owners outside these cities should contact their local wastewater utility directly. Smaller Iowa towns often adopt the same federal pretreatment language. But they enforce it with their own pumping schedules and fee amounts. Always verify with your local utility before assuming a published schedule applies.

Installation and Sizing Requirements

Iowa cities use model plumbing codes to size grease interceptors. The 2024 Uniform Plumbing Code (UPC) from IAPMO splits interceptors into two types: hydromechanical grease interceptors (HGIs), which are smaller indoor units, and gravity grease interceptors (GGIs), which are larger outdoor vaults.

For HGIs, UPC §1014.2.1 caps the flow rate at no more than 50 gpm and no less than 20 gpm without AHJ approval. The total fixture capacity draining into an HGI cannot exceed 2.5 times the certified gpm flow rate. UPC Table 1014.2.1(1) sets max full-pipe flow: 20 gpm for a 2-inch pipe, 60 gpm for a 3-inch pipe, and 125 gpm for a 4-inch pipe (UPC Table 1014.2.1(1)).

For GGIs, UPC §1014.3.6 sets minimum volume by Drainage Fixture Units (DFUs):

• 500 gallons for 8 DFUs
• 750 gallons for 21 DFUs
• 1,000 gallons for 35 DFUs
• 1,250 gallons for 90 DFUs

UPC §1014.3.4 requires gravity interceptors outside the building unless the AHJ approves a ventilated indoor location. Most Iowa cities use these sizing rules as written.

Des Moines adds a hard local minimum on top of the UPC baseline. The WRA's Grease Interceptor Sizing Proposal form states that new interceptors must be no less than the ordinance minimum of 1,000 gallons (WRA Grease Interceptor Sizing Proposal). The WRA uses a peak-meals-per-hour formula to size units. But the 1,000-gallon floor applies to every new install regardless of meal volume. Even low-volume kitchens must meet this minimum.

Where the International Plumbing Code applies, IPC §1003.3.1 requires a grease interceptor for fixtures in food prep areas. This covers pot sinks, prerinse sinks, soup kettles, wok stations, and floor drains. The IPC defines a Gravity Grease Interceptor as a unit of not less than 500 gallons (IPC Chapter 2). Iowa's local 1,000-gallon minimum sits above that floor.

HGIs are certified under ASME A112.14.3 for units rated at 100 gpm or less. The standard requires average grease retention of at least 90%, incremental efficiency of at least 80%, and retention of at least 2 pounds of grease per 1 gpm. Mechanical grease removal devices are tested under ASME A112.14.4. PDI G-101 from the Plumbing & Drainage Institute is also widely accepted.

Cleaning and Maintenance Frequency

The 25% Rule drives every Iowa pumping schedule. When FOG and settled solids exceed 25% of the interceptor's liquid depth, the clear zone shrinks. Grease passes straight through to the sewer. This standard appears in CSA B481.4 and is used by FOG programs across the U.S.

Iowa cities set required pumping schedules based on the 25% Rule. The Des Moines WRA enforces the 25% threshold or a three-month maximum, whichever comes first (Des Moines WRA FOG Program). WRA inspectors check both indoor traps and outdoor interceptors. They require three years of maintenance records on site during any inspection. Missing records are a violation even if the trap is clean.

Sioux City is stricter for indoor units. Indoor traps rated 20 to 55 gpm must be pumped weekly or when the 25% threshold is reached — whichever is first. Outdoor interceptors of 500 gallons or more must be pumped quarterly or when the 25% threshold is reached (Sioux City FOG FAQs). The weekly indoor rule reflects how quickly small units fill versus underground vaults. Small traps can reach 25% within a few days at high-volume locations.

Owners in Davenport, Cedar Rapids, Iowa City, and other cities should check with their local AHJ. The 25% Rule is the universal trigger, but minimum intervals vary by city.

The Massachusetts Health Officers Association recommends monthly inspection and pumping by a licensed hauler when FOG and solids hit 25%, or at least every three months. Most Iowa POTWs follow that same pattern. This guidance aligns with what Des Moines and Sioux City codify in their sewer ordinances.

Record-Keeping and Manifest Requirements

Federal law sets a hard floor on records. Under 40 CFR §403.12(o)(2), industrial users in the National Pretreatment Program must keep monitoring records for at least three years. That window extends if there is unresolved litigation. A Control Authority that grants a monitoring waiver must keep the supporting records for three years after the waiver ends (40 CFR §403.12(e)(2)(iv)).

For Iowa restaurants: every pump-out gets a manifest. Keep each manifest for at least three years. All records must be on site during a city inspection. A complete manifest includes:

• Date and time of service
• Volume removed in gallons
• Hauler company name and license number
• Destination disposal facility
• Condition of the interceptor at the time of service

The Des Moines WRA requires three years of maintenance records on site for inspector review (Des Moines WRA FOG Program). The WRA also charges a $50.00 fee for routine FOG compliance inspections.

Where self-monitoring is required, 40 CFR §403.12(g) requires sample collection to follow federal pretreatment protocols. Most restaurants use a licensed hauler. The hauler's standard manifest forms are built to satisfy both federal and local POTW reporting rules.

Fines and Penalties

Fine schedules in Iowa are set by individual cities — not by a statewide grid. The verified figures from primary sources are limited. Treat any unsourced fine table you find online as unverified until you confirm it with your AHJ.

The Des Moines WRA enforces non-compliance through notices of violation. Some notices carry no fine. Others carry fixed fines of $100 or $200. There may also be civil penalties or cleanup cost recovery for blockages and sanitary sewer overflows (Des Moines WRA FOG Program). The WRA can also require a compliance plan or a properly sized outdoor interceptor.

Sioux City applies a wider fine range. Non-compliant businesses can face penalties from $100 up to $1,000 per violation, plus possible termination of city utility services in serious cases (Sioux City FOG FAQs). Loss of sewer service effectively stops restaurant operations.

For Davenport, Cedar Rapids, Iowa City, and other cities, no specific fine grid appears in primary sources. Contact your AHJ to verify current amounts. Davenport's sewer ordinance requires immediate notice of accidental prohibited discharges. A written report is due within five days. It must cover the cause, duration, and corrective steps (Davenport Sewer Ordinance §13.16.200). Failure to report is a separate violation.

Every municipal penalty traces back to 40 CFR §403.5, which bans obstructive discharges to POTWs. Cities that allow repeated FOG violations risk EPA action against the municipality itself. That is why local enforcement tends to escalate fast for repeat offenders. Ask your city wastewater utility for the current sewer use ordinance and verify the fine schedule in writing before relying on any published rate.