Side Sewer Backups

What is a sewer backup?

Sewer backups happen when sewage and/or dirty water (called wastewater) come up a sink, toilet or drain. They usually happen when something blocks the sewer pipe and prevents wastewater from flowing freely.

Sewer backups need to be stopped and cleaned quickly to eliminate exposure to potentially harmful bacteria and viruses.

If you have a sewer backup

1. Protect people from exposure. Turn off power to eliminate electrical hazards.

2. Call a plumber – View our Troubleshooting Your Sewer Problem (pdf) for tips and questions to ask your plumber. 

3. If your contractor thinks the issue is related to a potential blockage in the sewer mainline or connection, call Seattle Public Utilities at (206) 386-1800. We may come check the public sewer for issues.

4. Document any damage and keep copies of all invoices for cleanup-related costs. If the sewer backup was caused by a SPU sewer issue you can file a claim with the City for reimbursement of your costs. Select the Filing a Damage Claim webpage for more information on that process.

5. Clean up as soon as possible to protect people – especially small children – from bacteria and viruses.

6. Before attempting to clear your side sewer of a blockage, call Puget Sound Energy at 1 (888) 225-5773 in order to avoid damaging a gas line. View the PSE website for more information.

Sewage contains hazardous germs that can contaminate people and things. Take extra care to protect your home, family, pets and yourself from sewage.

Protect your home

  • Avoid flushing toilets or using other water appliances.
  • Do not try to stop the flow of sewage coming up through the floor drain or any other drain.
  • Discard items exposed to sewage.
  • Talk with your insurance agent about how to document damage and begin repairs.
  • Sanitize and repair, or remove and discard paneling, wallboard or wall coverings within 24 hours.
  • Clean and sanitize hard surfaces with hot water and mild dish detergent. Then rinse with eight tablespoons of liquid household bleach dissolved in one gallon of water. Let the surface air dry.

Protect yourself

  • DO NOT MIX CLEANERS! Mixing bleach and ammonia produces DANGEROUS FUMES!
  • Wear long sleeves, long pants, rubber boots, gloves and eye protection.
  • Avoid contact with sewage, especially in your mouth, eyes, nose, or any cuts or sores.
  • Keep cuts and sores clean and covered. If you should get cut while cleaning, talk to your doctor about getting a tetanus shot.
  • Do not eat or drink anything exposed to sewage.

Protect your family

  • Consider hiring a professional cleaning company.
  • Do not allow children or pets to play in contaminated areas.
  • Avoid carrying germs from the sewage into uncontaminated areas on your shoes.
  • After the clean-up, wash your hands thoroughly and launder clothes and shoes separately from other clothing.

Avoid danger

  • Do not use electrical equipment while standing in water.
  • Turn off power to the flooded area.
  • Turn off the gas (or other fuel) to your furnace or heater and hot water heater.
  • Unplug all electrical appliances and small electrical devices.
  • Call an expert to remove appliance motors, dry them, and inspect for damage before using again.

Other resources

Watch this sewer backup video for more information.

SPU’s role in sewer backups

If an SPU response crew is dispatched to investigate a sewer backup, they will work to determine the cause. They may:

  • Check the flow in the public sewer mainline, and
  • Perform a CCTV (video) inspection on the public sewer mainline

SPU will make repairs if the public sewer mainline is damaged or obstructed, or if the City’s part of the sewer connection has failed.
After their investigation, SPU crews will leave a door hanger at your property with a reference (work order) number. If you would like additional information about the SPU investigation please email us at and include the reference (work order) number.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

Newsletter Updates


Sign up for the latest updates from Public Utilities

Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.