Grease Trap Regulations in Washington

Overview

Washington food service businesss must follow federal, state, and local FOG rules. The federal foundation is the Clean Water Act and the National Pretreatment Program at 40 CFR Part 403. These rules ban solid or viscous pollutants that obstruct sewers. They also require Publicly Owned Treatment Works (POTWs) to set local pretreatment limits. All food service businesss must comply.

The Washington State Department of Ecology administers the federal program at the state level. Each utilities enforce specific FOG rules locally. Key utilities include Seattle Public Utilities, King County Industrial Waste, Tacoma Environmental Services, and the Spokane County Industrial Pretreatment Program.

For restaurant owners, four questions drive day-to-day compliance: what device is required, how often it must be cleaned, what records must be kept, and what discharge limits apply at the property line. The answers vary by jurisdiction. The sections below cite each rule to its primary source so operators can verify current requirements directly with the regulator that enforces them.

Governing Authorities

Washington's FOG enforcement starts with delegated federal authority. The Department of Ecology administers waste discharge permits under RCW 90.48.160 through RCW 90.48.200. These implement the federal Clean Water Act. Any commercial or industrial operation discharging wastewater to a POTW must obtain an industrial wastewater permit. The City of Fife's pretreatment guide documents this requirement [Fife Pretreatment].

Below the state level, each major utility runs its own pretreatment program. Key contacts include:

• Seattle Public Utilities enforces commercial kitchen FOG rules under the Seattle Municipal Code. The 100 parts-per-million discharge limit is at SMC 21.16.300. The maintenance mandate is at SMC 21.16.310.
• King County Industrial Waste regulates indirect dischargers feeding the regional wastewater system. It publishes specific limits including the 100 milligrams per liter cap on nonpolar FOG and controls on free-floating polar FOG [KCIW Limits].
• Tacoma Environmental Services administers the Grease Interceptor Sizing & Installation Policy under Tacoma Municipal Code 12.08C and allows service suspension under TMC 12.08.180.
• City of Spokane requires Significant Industrial Users to obtain a Wastewater Discharge Permit [Spokane Wastewater].
• Spokane County Environmental Services enforces grease control device requirements at SCC 8.03.5020, oil/water separator requirements at SCC 8.03.5040, and broader pretreatment authority under SCC Chapter 8.03A.
• City of Kent Public Works requires installation, operation, and maintenance of FOG removal devices for all FOG-generating facilities [Kent FOG].
• City of Yelm Public Works requires yearly check of grease interceptor maintenance to the City under its sewer development guidelines [Yelm Sewer Ch. 5].

Because pretreatment rules differ by city and county, always confirm requirements with the Authority Having Jurisdiction (AHJ) that issues your wastewater discharge permit before relying on guidance from a different utility.

Key Requirements

Across Washington's verified municipal codes, FOG compliance comes down to four core obligations. Clean the interceptor before it loses efficiency. Install and size it correctly. Keep records that prove maintenance happened. Meet the discharge level limit at the property connection.

Cleaning Frequency

The most widely codified maintenance trigger in Washington is the "25 percent rule." Tacoma's Grease Interceptor Sizing & Installation Policy under TMC 12.08C.500(5)(a) requires cleaning whenever 25 percent of the collection chamber fills with FOG or solids, or when grease is visible at the outlet tee.

Tacoma also distinguishes between device types. Gravity Grease Interceptors must be cleaned at least twice per year. Hydromechanical Grease Interceptors must be cleaned at least once per month [Tacoma Tip Sheet]. These minimums apply on top of the 25 percent trigger. Any unit that reaches the threshold sooner must be pumped sooner.

Seattle Municipal Code at SMC 21.16.310(A) requires food service businesses to install and maintain grease interceptors to minimize FOG entering the sewer. Maintenance frequency must keep the device functional. Seattle Public Utilities reinforces this through Best Management Practices for commercial kitchens — the guide haulers and inspectors use during site visits.

The City of Kent requires FOG-generating facilities to install, operate, and maintain FOG removal devices. These must capture polar and nonpolar sludge and solids before discharge to the public sanitary sewer [Kent FOG]. Spokane County's pretreatment program inspects regulated businesses to verify proper operation, maintenance, and recordkeeping of grease control and oil/water separation devices [Spokane FOG Control].

The 25 percent rule also has a federal basis. The standard at 40 CFR 403.5(b)(3) bans solid or viscous pollutants in amounts that cause obstruction. Local 25 percent thresholds are designed to satisfy this federal requirement.

Interceptor Sizing and Installation

Washington jurisdictions follow the Uniform Plumbing Code for sizing and local code for placement. Under UPC §1014.3.4, gravity grease interceptors must be installed outside the building unless the AHJ approves otherwise. This rule keeps sewer gases and odors out of food preparation zones.

Tacoma reinforces this standard for new construction. Gravity Grease Interceptors are generally installed in the ground outside the facility, upstream from the sanitary waste drain line, and are at least 500 gallons in capacity [Tacoma Tip Sheet]. All new construction food service businesss producing any amount of FOG must install an rightly sized Gravity Grease Interceptor under Tacoma's Municipal Code, the Grease Interceptor & Sizing Policy, and the Uniform Plumbing Code [Tacoma Sizing Policy].

Sizing for hydromechanical interceptors follows the flow-rate matrix in UPC §1014.2.1. The certified flow rate is capped at 50 gallons per minute. The minimum is 20 gallons per minute. Deviations require AHJ approval. Gravity interceptors are sized using Drainage Fixture Units under UPC §1014.3.6.

Spokane County places installation duty on the owner. SCC 8.03.5020 requires any commercial food facility generating grease waste to install an approved grease control device at the owner's expense and liability. The device must be accessible for maintenance. SCC 8.03.5040 separately requires oil/water separators for any facility discharging petroleum. This covers the distinction between polar (animal/vegetable) FOG and nonpolar (mineral or petroleum) FOG.

Chemical additives are prohibited. The City of Tacoma's FOG Best Management Practices Policy bans hot water above 140 degrees, steam, chemicals, and biological additives. These would cause fats, oils, and grease to release from the interceptor into the wastewater collection system [Tacoma BMP Policy]. King County also bans agents that emulsify free-floating polar FOG [KCIW Limits]. Emulsifiers do not remove FOG. They pass it through the baffles where it cools and re-congeals in the sewer line downstream.

Record-Keeping Requirements

At the federal level, 40 CFR 403.12(o)(2) requires Industrial Users to keep monitoring records for at least three years. The retention period extends during any unresolved litigation. Most local FOG programs anchor their recordkeeping rules to this baseline.

The City of Yelm requires check of grease interceptor maintenance to be provided to the City yearly and upon request. This is set in Chapter 5 of the Yelm Sewer Development Guidelines [Yelm Sewer Ch. 5]. Spokane County's FOG Control Program inspects businesses to verify proper operation, maintenance, and recordkeeping [Spokane FOG Control]. In Seattle, SPU requires food service businesses to install and maintain grease interceptors and to follow Best Management Practices, which inspectors review during compliance visits [SPU FOG].

In practice, the records that satisfies most utilities includes hauler manifests, pump-out invoices with date and volume, the licensed hauler's identification, and the disposal facility receipt. Keep these on-site and available during unannounced inspections. Confirm the exact retention window with your local AHJ before discarding older records.

Discharge Limits

Seattle and King County publish numeric discharge limits at the property line. SMC 21.16.300(A)(2) bans wastewater containing more than 100 parts per million by weight of fats, oil, or grease from the sanitary sewer.

King County Industrial Waste sets the nonpolar FOG limit at 100 milligrams per liter. This protects the sewage treatment process from mineral and petroleum pollutants [KCIW Limits]. Polar FOG is regulated separately. King County rules require samples to contain less than 0.25 inches of free-floating polar FOG. Dischargers may not add agents that emulsify this layer [KCIW Limits]. Some facilities discharging polar FOG must also complete a FOG control plan.

Spokane County's FOG Control Program aims to minimize and prevent FOG-related sewer blockages and interference from grease-producing commercial businesses [Spokane FOG Control]. The discharge prohibition is enforced through pretreatment device requirements rather than a single numeric ppm cap.

The 100 mg/L benchmark used by King County and most Washington utilities aligns with EPA national guidance. The EPA identifies 100 mg/L as the most commonly reported numeric local limit for FOG under POTW pretreatment programs (EPA-833-F-12-003).

Fines and Enforcement

Washington enforcement for FOG violations escalates from inspection notices to civil penalties to permit suspension. The exact penalty amounts are set in each utility's municipal code. Contact your utility directly for the current penalty schedule that applies to your location.

Seattle

Seattle uses cumulative civil penalties rather than a fixed scale. Civil penalties accrue up to $500 per day for ongoing violations until compliance is achieved. Specific violations are capped at $5,000 (SMC Ordinance 123494; 2021 Seattle Plumbing Code). Business owners can also be held responsible for any City costs to clean up grease-laden wastewater.

Seattle Public Utilities also requires corrective action plans, increased inspection frequency, and Best Management Practice training for kitchen staff. Cumulative daily penalties can grow quickly during prolonged noncompliance. Confirm the current schedule with SPU.

King County

King County Industrial Waste enforces compliance through inspections, increased monitoring, and equipment upgrade orders. It also uses public disclosure. Companies in significant noncompliance may be charged for increased monitoring. They may be required to upgrade equipment. Their company name will also be published in a Seattle Times display ad titled "Companies Violate Pretreatment Standards" (KCIW Brochure). This is an ongoing, documented enforcement tool used to deter repeat violations.

The Department of Ecology has authority under RCW 90.48.144 to impose civil penalties up to $10,000 per day for water quality violations. That cap shapes the upper bound of enforcement actions tied to the federal NPDES program. Confirm specific penalty amounts directly with King County Industrial Waste.

Tacoma

Tacoma's enforcement centers on the Director's power to halt service. TMC 12.08.180 allows the Director to suspend storm drainage services and wastewater treatment services. The Director may also suspend or revoke a wastewater discharge permit. This applies when a discharge presents an imminent danger to health, welfare, or the environment, or threatens the Municipal Sewer System.

Suspending wastewater service ends a restaurant's ability to operate. This makes it one of the most significant enforcement tools in the state. It typically follows documented noncompliance with the 25 percent rule, the chemical additive ban, or the maintenance schedule for Gravity or Hydromechanical interceptors.

Spokane County

Spokane County's pretreatment program is established under SCC Chapter 8.03A. It allows issuance of wastewater discharge permits, compliance monitoring, and enforcement. The County issues remedial action requirements for uncorrected, repeated, and serious FOG violations. Specific penalty amounts are determined case-by-case through admin review.

Additional Consequences

Beyond civil penalties, Washington utilities can require installation of more advanced pretreatment equipment, increased inspection frequency with associated fees, and immediate cease-and-operation orders. If a discharger causes a sanitary sewer overflow, local officials can require the business to stop operation. The owner must also clean the trap and clear the affected plumbing at their own expense (40 CFR §403.5(a) Pretreatment Standards: General Prohibitions).

The EPA's 2004 Report to Congress on CSOs and SSOs provides the federal context (EPA-833-R-04-001). It found that 74 percent of sanitary sewer overflows were caused by blockages. Of those blockages, 47 percent were caused by grease from restaurants, homes, and industrial sources. This is why many POTWs adopt strict local FOG limits.

Major City FOG Programs

Seattle

Seattle Public Utilities operates one of the most documented FOG programs in the Pacific Northwest. Seattle Municipal Code has two anchor rules. The first is the discharge limit at SMC 21.16.300(A)(2). It bars wastewater with more than 100 parts per million by weight of fats, oil, or grease. The second is the maintenance mandate at SMC 21.16.310(A). It requires food service businesses to install and maintain interceptors to minimize FOG entering the sewer.

Civil penalties accrue up to $500 per day for ongoing violations until compliance is restored. Specific violations are capped at $5,000 (SMC Ordinance 123494). Owners are also responsible for any City costs to remediate damage caused by grease-laden discharges.

Tacoma

Tacoma Environmental Services has one of the more detailed FOG schedules in the state. Under the Tacoma Municipal Code, the Grease Interceptor & Sizing Policy, and the Uniform Plumbing Code, all new food service businesss producing any FOG must install an rightly sized Gravity Grease Interceptor [Tacoma Sizing Policy].

The cleaning trigger at TMC 12.08C.500(5)(a) requires service whenever 25 percent of the chamber fills with FOG or solids, or when grease is visible at the outlet tee. Minimum pumping schedules are twice per year for Gravity Grease Interceptors and once per month for Hydromechanical Grease Interceptors [Tacoma Tip Sheet]. The Director's suspension authority under TMC 12.08.180 backs the schedule with the ability to halt wastewater service for noncompliance.

King County

King County's regional wastewater system relies on a 100 mg/L nonpolar FOG limit and tight controls on free-floating polar FOG. These are published in the County's wastewater discharge limits and regulations [KCIW Limits]. Some businesses discharging polar FOG may need to develop a FOG control plan to show that free-floating FOG stays under the legal threshold.

The County's enforcement program requires publication of significant noncompliance in the Seattle Times. The recurring display ad is called "Companies Violate Pretreatment Standards" (KCIW Brochure). Companies receiving fines may also be charged for increased monitoring and required to install upgraded equipment.

Spokane

The City of Spokane requires all Significant Industrial Users to obtain a Wastewater Discharge Permit. This includes those generating pollutants capable of disrupting treatment processes [Spokane Wastewater]. At the county level, SCC 8.03.5020 requires every commercial food facility generating grease waste to install an approved grease control device at the owner's expense and liability. SCC 8.03.5040 separately requires oil/water separators for any facility discharging petroleum.

The Spokane County Industrial Pretreatment Program implements these requirements through inspections, permitting, enforcement, and admin review, with pretreatment authority defined under SCC Chapter 8.03A.

Frequently Asked Questions

How often must I clean my grease trap in Washington?

The most universal trigger is the 25 percent rule. In Tacoma, TMC 12.08C.500(5)(a) requires service whenever the chamber reaches 25 percent of capacity with FOG or solids, or when grease is visible at the outlet tee. Tacoma also publishes minimum pumping schedules: twice per year for Gravity Grease Interceptors and once per month for Hydromechanical Grease Interceptors [Tacoma Tip Sheet]. In Seattle, food service businesses must maintain interceptors under SMC 21.16.310(A) at a frequency that prevents FOG from entering the sewer. Always confirm the schedule with your local utility. The rule that applies depends on the AHJ for your address.

What records must I keep for grease trap maintenance?

At the federal level, 40 CFR 403.12(o)(2) requires Industrial Users to keep monitoring records for at least three years. The retention period extends during any unresolved enforcement litigation. Local rules add to this baseline. The City of Yelm requires check of grease interceptor maintenance to be provided to the City yearly and upon request [Yelm Sewer Ch. 5]. Spokane County inspects businesses to verify proper recordkeeping for grease control and oil/water separation devices [Spokane FOG Control]. Keep hauler manifests, pump-out invoices, and disposal facility receipts on-site and available for inspection.

Can I use chemical additives to reduce grease in my trap?

No. The City of Tacoma's FOG Best Management Practices Policy bans hot water above 140 degrees, steam, chemicals, and biological additives. These would cause fats, oils, and grease to release from the interceptor into the wastewater collection system [Tacoma BMP Policy]. King County also bans agents that emulsify free-floating polar FOG [KCIW Limits]. Emulsifiers do not eliminate FOG. They pass it through the baffles where it cools and re-congeals downstream. Mechanical pumping by a licensed hauler combined with kitchen Best Management Practices is the only acceptable method.

Find Grease Trap Service in Washington

Washington maintains strict FOG compliance requirements to protect Puget Sound and the state's freshwater systems. Our directory currently lists 33 qualified grease trap service providers across Washington. They understand state Department of Ecology standards and local utility requirements. Certified haulers provide proper records, support recordkeeping, and dispose of waste at approved facilities — all required to keep your operation compliant. Find a provider in your area by visiting our Washington grease trap service directory.