Prepared by GreaseTrapLocator · Fact review: October 17, 2026
How grease contributes to a backup
FOG can solidify, reduce sewer capacity, and block flow in plumbing and sewers. EPA's cited 2004 data identifies grease as the most common cause—47%—of reported blockages. It does not say grease caused 47% of all sanitary sewer overflows.
Who determines responsibility?
The investigating utility or authority, the location and cause, governing law, permits, property and service agreements, maintenance history, and incident facts may all matter. GTL does not determine legal fault, prove whose grease caused a blockage, interpret an insurance policy, or predict a lien, fine, or cleanup bill. In Canada, check the provincial or territorial and municipal rules that apply.
Preserve useful evidence
- Time, location, affected fixtures and areas, and immediate actions.
- Utility and public-health reference numbers and written direction.
- Photos or video of what you can see safely (never open, enter or lean into the trap), plumbing diagrams, approved plans, and service records.
- Contractor cause assessment, repair documents, and replaced components.
- Cleanup, product disposition, inspection, and reopening records.
- Property, lease, service-contract, broker/insurer, and legal communications.
Make the required notifications
If sewage backs up into the restaurant, close the food establishment immediately as a precaution and contact the health authority for instructions on cleanup and reopening. Report the backup to the sewer utility and follow its direction. Notify the property contact, broker/insurer, or other party as the actual agreement requires. Preserve deadlines and avoid guessing about coverage or fault. If a claim or demand arises, obtain local legal advice.
Prevent a repeat
Correct the identified cause, update the approved maintenance program, repair damaged components, retrain staff on prohibited discharges, and review whether menu, volume, fixtures, or equipment changed the system loading.
Official sources used
U.S. Environmental Protection Agency
FOG can solidify, reduce sewer capacity, and block flow; 40 CFR 403.5(b)(3) prohibits solid or viscous pollutants in amounts that obstruct flow and result in interference; local programs establish controls.
Controlling Fats, Oils, and Grease Discharges from Food Service Establishments · reviewed October 17, 2026
U.S. Environmental Protection Agency
Grease was the most common cause, 47 percent, of reported blockages; this is not 47 percent of all sewer overflows.
Controlling Fats, Oils, and Grease Discharges from Food Service Establishments · reviewed October 17, 2026
New York City Department of Environmental Protection
When businesses discharge animal fats and vegetable oils into the sewer, it can cause sewer backups; the City requires grease-generating businesses to install, operate and maintain properly sized grease interceptors, and asks that sewer backups be reported to 311.
Disposing of Grease as a Business · reviewed October 17, 2026
Seattle Public Utilities
Seattle requires cleaning per the manufacturer's specifications; if they are not available, no more than 25 percent of an interceptor should contain food or FOG buildup. It prohibits emulsifying agents, enzymes and bio-additives in interceptors, and says a business with a backup into the premises should immediately close and contact Seattle-King County Public Health.
Fats, Oils, & Grease: Commercial Kitchens · reviewed October 17, 2026
U.S. Food and Drug Administration
Section 8-404.11 lists sewage backup among emergencies where an imminent health hazard may exist, requiring the permit holder to immediately stop operations and notify the regulatory authority (unaffected areas may keep operating); section 8-404.12 requires the authority's approval before resuming.
2026 Food Code · reviewed October 17, 2026
Frequently asked questions
Who decides whether the restaurant is responsible for a grease-related sewer backup?
The investigating authority, governing law, agreements, cause, location, and incident facts control. No universal conclusion is possible.
Can a laboratory prove which restaurant caused the blockage?
Do not promise that. Investigation methods and evidentiary value depend on the incident and the responsible authority or qualified expert.
Will insurance cover the cleanup?
Coverage depends on the actual policy, endorsements, exclusions, notice requirements, cause, and facts. Contact the broker or insurer and do not assume coverage.
What records should be preserved?
Keep authority references, photos of what you could see safely, approved plans, maintenance records, contractor findings, repairs, cleanup, reopening, and relevant agreement communications.
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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