Sewer Backup: What to Do First, Step by Step
The first hour decides how much damage a sewage backup does and how safe your house stays.
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The short answer
Stop using water, keep people and pets away from the sewage, and call a plumber. Every gallon you run down a blocked line has to go somewhere, and it comes out of the lowest fixture in the house. Do not try to flush, plunge or chemically dissolve a main line backup.
Sewage carries bacteria and other germs, so treat it as a health problem as well as a plumbing one. The steps below are in the order that protects you first and your property second.
Do these first
- Stop running water: no toilets, showers, dishwasher or washing machine
- Keep children, pets and anyone with a weak immune system out of the area
- Wear rubber gloves and boots if you must go in, and wash well afterward
- Turn off the electricity to the area only if you can reach the panel without stepping in water
- Open windows for ventilation if it is safe to do so
- Call a plumber and say which fixtures backed up first
Why the lowest drain backs up first
A sewer backup shows up at the lowest opening in the house, usually a floor drain, a basement or ground-floor shower, or the toilet nearest the slab. That is gravity at work. If the blockage is in your line, water rises until it finds the first outlet.
It also tells the plumber where to look. If only one bathtub backs up, the blockage may be in a branch line. If several fixtures go at once, the main line to the street is the likely place. That is the information to give on the call.
Whose problem is it?
Where the blockage sits decides who fixes it.
| Where the problem is | Who usually handles it | What to do |
|---|---|---|
| Inside the house, in a branch line | Homeowner, or the landlord for a rental | Call a plumber to clear the line |
| In the lateral between the house and the main | Usually the homeowner | Plumber clears it, and a camera finds the cause, see sewer camera inspection |
| In the public sewer main | The sewer district or city | Call the district if neighbors are also affected |
| In a septic tank or field | The property owner | Stop water use and call a septic professional |
What the plumber will do
The first job is to get the line flowing again, which usually means cabling the line from a cleanout. If the cause is grease or scale, jetting may follow. If it is roots or a broken pipe, the plumber will tell you what the camera shows and what the repair options are. See sewer line repair for what those involve.
Ask for the camera recording. A recording tells you whether this was a one-time blockage or a sign of a failing line, and it is useful to a landlord or an insurer.
Cleanup and hazards
Anything porous that has been soaked with sewage, such as carpet, padding and drywall, generally cannot be cleaned safely and is often removed. Hard surfaces can be disinfected. The damage can go beyond what you can see, so a professional cleanup is worth considering. Our water damage restoration page covers the drying and disinfecting that follows a backup.
Insurance and renters
Many homeowners policies exclude sewer backup unless it has been added as an endorsement, so check your policy today rather than after a loss. Photograph the damage before cleanup, keep receipts and report the loss promptly.
If you rent, tell the landlord in writing right away, with photos and the date. California law requires landlords to keep the sewer system in working order, and a written record protects you.
Warning signs before a backup
- Gurgling in a toilet or tub when another fixture drains
- Slow drains in more than one fixture at the same time
- A sewer smell inside the house or near the cleanout
- A wet or unusually green strip of yard above the sewer line
- Water pooling in a floor drain after a load of laundry
How to make the next one less likely
Keep grease and wipes out of the line. Wipes sold as flushable do not break down like paper and are a common cause of blockages. Do not flush anything other than toilet paper and human waste, and pour cooking grease into a can, not the sink.
If roots are the cause, a repair is the fix and cleaning is only a pause. Make sure your cleanout is accessible and not buried under landscaping, since it is the first place a plumber will go. Some homes with a history of backups add a backwater valve, a device that stops sewage from flowing back into the house from the main. It is installed by a plumber, and a permit may apply.
When to call the sewer district
If your neighbors also have backups, or the cleanout shows the line is clear up to the street, the blockage may be in the public main. In that case the sewer district or city is the right call, and it is worth telling the plumber what you found so time is not spent on your own line.
What to tell the dispatcher
Give the address, the fixtures that backed up and in what order, and whether the backup is still rising. Say if anyone in the home is elderly, pregnant or has a weakened immune system, since that changes how urgent the cleanup is. Mention if the house has a cleanout and whether you have already opened it.
Questions about this topic
No. It rarely works on a main line and it can splash or burn skin. It also makes the plumber's work riskier.
It can be. It carries bacteria and other germs, so keep people and pets away, wear gloves and wash well.
If neighbors are affected too, the main may be involved. A plumber can check your cleanout to see where the blockage sits.
Only if your policy covers it, often through an endorsement. Read your policy and photograph everything.
No. Every gallon you run adds to the backup until the line is cleared.
Related guides
Drain Cleaning Cost in Sacramento County, CA: What to Expect
National price ranges, the factors that move the bill and how to tell a fair quote from a padded one.
Sewer Camera Inspection When Buying a Home in California
A standard home inspection does not look inside the sewer line. A camera does, before you own the problem.
Does Homeowners Insurance Cover Plumbing Leaks in California?
Sudden leaks are often covered for the damage they cause. Slow leaks and worn pipes usually are not.
Need a plumber now?
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