Prepared by GreaseTrapLocator · Fact review: August 8, 2026
What “25%” can mean
A local program may compare accumulated FOG and solids with operating depth, effective volume, or another defined part of the device. Those are not interchangeable measurements. The rule may also be paired with a maximum time between services, a manufacturer schedule, or written permission for an adjusted interval.
Two official examples show the difference
Connecticut permit example
Connecticut's general permit (effective October 5, 2025) uses 25% of operating depth or service every three months, whichever is more frequent, for the specified outdoor in-ground equipment. It also describes records retained for five years.
Seattle example
Seattle directs businesses to follow manufacturer specifications and, when those are unavailable, limits food or FOG buildup to 25% of the interceptor. Seattle's program also contains its own cleaning and reporting rules.
These examples prove that a 25% concept exists. They do not make either jurisdiction's details the rule for another facility.
Questions to resolve locally
- Which devices and chambers are covered?
- Does the rule use depth, effective volume, or another measure?
- Are FOG and settled solids combined?
- Is there a separate maximum time between services?
- Who may inspect, measure, clean, transport, and dispose?
- What service records and retention period are required?
Safe compliance workflow
Keep the official rule with the facility records. Use a qualified service provider or the locally authorized safe process. Record the result, service performed, defects, disposal documents where required, and the next locally determined review date. Do not lean over an open vault or improvise a dipstick method from a generic web article.
Official sources used
Connecticut Department of Energy and Environmental Protection (DEEP)
The cited permit uses 25 percent of operating depth or three months, whichever is more frequent, requires specified records for five years, and prohibits intentionally using hot water, steam, chemicals, or biological additives to release FOG.
General Permit for the Discharge of Wastewater Associated with Food Establishments (effective October 5, 2025) · reviewed October 16, 2026
Seattle Public Utilities
Seattle uses a 25 percent trigger when manufacturer specifications are unavailable, prohibits emulsifying agents/enzymes/bio-additives, supplies local self-cleaning guidance, and directs a business with a backup into the premises to close and contact public health.
Fats, Oils, & Grease: Commercial Kitchens · reviewed August 8, 2026
U.S. Occupational Safety and Health Administration
Smell is not a reliable warning. Evaluate hydrogen-sulfide and confined-space hazards and apply the monitoring, training, entry controls and respiratory protection required by the applicable standards and site assessment.
Hydrogen Sulfide: Evaluating and Controlling Exposure · reviewed August 8, 2026
U.S. Occupational Safety and Health Administration
Pits, tanks, vaults, and similar spaces may require hazard evaluation, controlled entry, monitoring, attendants, and rescue planning.
Protecting Construction Workers in Confined Spaces · reviewed August 8, 2026
Frequently asked questions
Is the 25% rule a nationwide law?
No. It is used in some local programs and permits, but the measurement, affected devices, service schedule, and records differ.
Does 25% mean operating depth or liquid volume?
It depends on the controlling rule. Do not substitute one measurement basis for another.
Can restaurant staff measure it themselves?
Only when the local rule and site safety program permit a safe method for that device. Never enter or lean into an interceptor, vault, or pit.
Does staying below 25% replace a time-based cleaning rule?
Not necessarily. Some programs pair an accumulation trigger with a maximum interval or manufacturer requirement.
Author: Grease Trap Locator Editorial Team
The Grease Trap Locator editorial team covers FOG compliance, grease trap maintenance, and commercial kitchen regulations across the US and Canada. Our guides are written for restaurant owners, facility managers, and food service operators who need practical, accurate information without the fluff.
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