Emergency plumbing
Sewer backup
Short answer
When sewage backs up into your home, stop using all water, keep people and pets away, and call a plumber to clear the main line. Sewage is contaminated water: porous materials it soaks, like carpet and drywall, generally need to be removed, and a professional cleanup is recommended for anything beyond a small area.
Updated · Editorial team; not yet technically reviewed
Sewer Backup at a glance
- First actions
- Stop all water use; keep away from the sewage; call a plumber.
- Where it shows up
- The lowest drains: basement floor drains, lower-level tubs, showers and toilets.
- Common causes
- Main line clogs, roots, a broken or sagging lateral, or an overloaded city sewer during heavy rain.
- Prevention
- Backwater valve, routine cleaning for root-prone lines, nothing but toilet paper flushed.
What to do right now
Stop using water
No flushing, showers, laundry, or dishwasher. Every gallon you use can come out of the lowest drain.
Protect people
Keep children and pets away. Wear waterproof gloves and boots if you must enter the area, and wash thoroughly after.
Electrical safety
Don't stand in water near outlets or appliances. Shut off power to the area at the panel only if you can reach it from a dry spot.
Call a plumber
They'll clear the main line through a cleanout and, if it recurs, inspect it with a camera.
Why sewers back up
| Cause | Clues |
|---|---|
| Clog in your main line | Only your home affected; worse when you use water |
| Roots in the lateral | Older clay or cast iron line, trees nearby, recurring clogs |
| Broken or sagging pipe | Clogs return quickly after cleaning; see sewer line repair |
| City sewer surcharge | Happens during heavy rain; neighbors affected too; call the sewer utility |
Cleanup
Water restoration standards treat sewage as the most contaminated category of water. Hard, non-porous surfaces can be cleaned and disinfected, but saturated carpet, pad, drywall and insulation are usually removed. Small backups limited to a tile floor can be cleaned with care; larger ones call for a professional restoration company. Photograph everything before cleanup for insurance.
Preventing the next one
- Backwater valve: a valve on the main line that closes if sewage flows backward from the city side. It needs periodic checking; many cities require a permit to install one, and some offer rebates.
- Maintenance cleaning: for lines with a root history, periodic cleaning helps prevent sudden blockages.
- Repair the cause: a camera inspection shows whether a crack or sag is the underlying problem.
- Insurance: sewer backup is often excluded from standard homeowner policies and sold as an endorsement. Check yours.
Problems that lead to sewer backup
- Drain backing upWhen water rises in a tub, shower or floor drain from another fixture, the main line is blocked. How to confirm it, what to stop doing and how it's cleared.
- Basement floodingWhether basement water is groundwater, sewer backup or a burst pipe changes what you do first. How to tell, how to stay safe, and how to prevent the next one.
Common questions
Is a sewer backup covered by homeowners insurance?
Often only with a sewer/water backup endorsement. Standard policies commonly exclude it. Check your policy or ask your agent.
Who is responsible if the city sewer caused the backup?
Rules vary. Report it to your sewer utility right away; some have claims processes. Backups from your own lateral are usually the owner's responsibility.