Sewage Backup in the House: Causes, Health Risks, Cleanup, Insurance

A sewage backup happens when wastewater cannot flow out through your sewer line and is pushed back into the house, usually through the lowest drain: a basement floor drain, shower or toilet. If you have a sewage backup, stop using water in the house, keep people and pets away from it, avoid touching it without gloves and boots, and call a plumber to clear the line. Untreated sewage contains bacteria, viruses and parasites, so anything porous it soaks into usually has to be thrown away, and everything else needs cleaning and disinfecting before it is dried.

What is a sewage backup?

Every drain in your home empties into one main pipe, called the building sewer or sewer lateral, which runs out to the city sewer main or to a septic tank. When that path is blocked or overloaded, wastewater has nowhere to go but back up the lowest openings in the house. A sewage backup outside (sewage coming up through a yard cleanout or soggy spots over the line) and one inside the house usually have the same causes.

The IICRC, which publishes the water damage restoration standard used by the industry, classifies sewage and waste line backflows as Category 3 water: grossly contaminated and able to carry harmful agents. That classification is why sewage cleanup involves more protective gear and more material removal than a clean-water leak.

What causes sewage to back up into a house?

The Indiana Department of Health and the Insurance Information Institute describe the same common causes:

The Insurance Information Institute notes that connecting French drains, sump pumps and other flood control systems to the sanitary sewer is illegal in many places and contributes to clogs. It also warns that paper towels, wipes, diapers and feminine products do not break down quickly in pipes. The Indiana Department of Health adds that too much rain getting into leaky sewer pipes, inadequate system capacity and poorly designed systems can all cause sanitary sewer overflows.

Who is responsible: you or the city?

It depends on where the problem is. The Insurance Information Institute says the sewer lateral is generally owned and maintained by the property owner, including the part that runs to the street. Blockages in the public main are a city problem. If water is rising quickly in your basement and you suspect the city main, the III advises calling your city's public works office right away. Local rules vary, so ask your sewer utility.

Health risks of sewage

The Indiana Department of Health warns that untreated sewage contains bacteria, viruses and parasites. According to that guidance, contact can cause skin infections and rashes, and swallowing contaminants from unwashed hands or contaminated surfaces can cause nausea, abdominal pain, vomiting and diarrhea. Breathing airborne microorganisms during cleanup can also cause respiratory problems and allergic reactions. The CDC lists wound infections, gastrointestinal illness and tetanus among the health concerns from contaminated floodwater.

People at higher risk should stay out of the cleanup. EPA advises that people with asthma or weakened immune systems avoid moldy sites, and that children and pregnant people should not take part in flood cleanup. If anyone develops symptoms such as vomiting, diarrhea, fever, or a wound that becomes red, swollen or draining after contact with sewage, contact a doctor. This guide is general information, not medical advice.

What to do right away when the sewage line backs up

1. Stop using water. No flushing, showers, laundry or dishwasher. Every gallon you send down the drain can come back up.
2. Keep everyone out. Keep children and pets away from the area.
3. Turn off electricity to the area if water is near outlets or appliances and you can reach the breaker safely without standing in water.
4. Protect yourself. Wear waterproof boots, gloves, eye protection and washable or disposable clothes, plus a mask, as the Indiana guidance recommends.
5. Call a plumber for the sewage backup. A plumber can find and clear the blockage from a cleanout and, if needed, run a camera down the line to look for roots or a break. If several neighbors have the same problem, call the city.
6. Document the damage. Photograph the water, the drain it came from and damaged items before cleanup, and keep receipts.
7. Call your insurer as soon as possible.

Where is the main drain cleanout?

The sewage cleanout pipe is a capped pipe that gives access to the main line. It is often found in the basement floor or wall near where the main line leaves the house, or outside near the foundation or along the line to the street. If you cannot find it, a plumber can.

Sewage backup cleaning: step by step

Small, fresh backups on hard floors are sometimes handled by homeowners. The Indiana Department of Health guidance describes these steps:

1. Remove standing wastewater with a mop, wet vac or squeegee, and lower humidity by opening up the house.
2. Open closets and cabinets and use fans and dehumidifiers to move air. Do not run whole-house air conditioning or furnace blowers if ducts were in the wastewater.
3. Throw away contaminated food, cosmetics, stuffed animals and baby toys, plus mattresses, pillows, foam items, upholstered furniture, books and most paper. Seal discarded items in heavy plastic bags.
4. Wash and disinfect walls, floors and washable items. The Indiana guidance recommends one-quarter cup of chlorine bleach per gallon of water, left in contact for at least one minute, then rinsed. Never mix bleach with ammonia; the guidance warns this forms toxic gases.
5. Wash clothing and small rugs in hot water, with bleach if the fabric allows.
6. Remove wet drywall and insulation if damage was extensive or cleanup was delayed. The guidance notes that wallboard wicks moisture above the water line and contaminants can dry inside the wall.
7. Clean and dry concrete thoroughly; sewage does not damage concrete the way it damages wood and drywall, but it does soak in.

Wall-to-wall carpet that gets wet usually has to be discarded, and foam padding nearly always does. See our guide to wet carpet after water damage.

When to call professionals for sewage cleanup

Consider a professional sewage cleanup company when the backup covers more than a small hard-floor area, reached drywall, carpet or a finished basement, sat for more than a day, or when anyone in the home is at higher risk. The Indiana guidance notes that drying an enclosed area such as a basement can take several weeks and that microorganisms keep growing while humidity stays high. Restoration companies use containment, protective equipment and moisture meters to confirm materials are dry. Damp areas left behind can lead to basement mold.

How to prevent a sewer backup

• Keep grease out of drains. The III recommends pouring cooking oil into a heat-resistant container and throwing it away once it cools.
• Flush only toilet paper. No wipes, diapers, paper towels or hygiene products.
• Deal with roots. Have roots cut periodically by a professional, or replace an old lateral with plastic pipe, which the III says resists root entry.
• Disconnect illegal connections. Make sure sump pumps, downspouts and French drains do not drain into the sanitary sewer.
• Install a backwater valve. FEMA advises having a licensed plumber install sewer backflow valves on pipes entering the home. The III notes a properly installed and maintained valve lets sewage out but not back in.
• Plug or protect floor drains. FEMA also lists installing drain plugs in basement floor drains.

Does insurance cover a sewage backup?

Often not, unless you added coverage.

• Homeowners insurance: The Insurance Information Institute states that sewer backups are not covered under a typical homeowners policy. Coverage is usually available as an endorsement, sometimes called water backup or sewer and drain backup, at a small added cost.
• Flood insurance: Coverage depends on the cause. FloodSmart says NFIP policies can cover damage from a sewer that backed up during a heavy rainstorm in a flood event, but not a backup caused by clogged pipes.
• Document everything. The III recommends before-and-after photos, a home inventory, itemized losses and saved receipts.

Our guide to water damage insurance claims explains the claim process, and what to do after water damage covers the first 48 hours.

How much does it cost to clear a backed-up sewer and clean up?

There are two separate bills: the plumber who clears the line and the cleanup. The plumbing cost depends on where the blockage is, whether a cleanout is accessible, whether a camera inspection is needed, and whether the line must be repaired or replaced. Cleanup cost depends on the area affected, how long the sewage sat, which materials must be removed, and drying time. We did not find a reliable published national price range for these jobs, so get written estimates. See water damage restoration cost for how restoration estimates are built.

Getting help

Flood Rescue Pros is a free service that connects homeowners with independent local restoration companies. Get help now or see service areas. For what professional sewage cleanup involves, see our main page.

Frequently asked questions

What should I do if the sewage line is backed up?

Stop using all water in the house, keep people and pets away, turn off power to the area if it is safe, and call a plumber to clear the line. If neighbors have the same problem, call the city's public works or sewer department.

Can you shower if your septic tank is backed up?

No. Any water you use goes into the same blocked system and can come back up through the lowest drain. Stop using water until the tank is pumped or the line is cleared.

Is sewage backup dangerous?

Yes. Untreated sewage contains bacteria, viruses and parasites that can cause skin infections and stomach illness. Wear protective gear, keep vulnerable people away, and see a doctor if you develop symptoms.

Where is the main drain located in a house?

The main drain cleanout is often in the basement floor or wall near where the sewer line exits, or outside near the foundation. It is a capped pipe; if you cannot find it, a plumber can.

Does homeowners insurance cover sewage backup cleaning?

Not under a typical policy. You need a water backup or sewer backup endorsement, according to the Insurance Information Institute.

Key facts

• A sewage backup occurs when the sewer line is blocked or overloaded and wastewater comes up the lowest drain in the house.
• Sewage is Category 3, grossly contaminated water under the IICRC standard; it contains bacteria, viruses and parasites.
• Stop using water, keep people out, wear boots, gloves and eye protection, and call a plumber.
• Discard porous items that soaked up sewage; disinfect hard surfaces and never mix bleach with ammonia.
• The property owner generally owns the sewer lateral; the city handles the public main.
• Typical homeowners policies exclude sewer backup; an endorsement adds coverage, and a backwater valve helps prevent repeats.