Sewage Backup in the Basement: Health Risks and Safe Cleanup

If sewage backs up into your basement, keep everyone out, stop using water in the house and shut off power to the area if you can do so safely. Sewage is Category 3 black water that carries bacteria and viruses. Porous items it touched must usually be thrown out, and the space needs professional cleaning, disinfecting and drying.

By West Chester Flood Cleanup Editorial Team · Published 2026-11-05

A sewage backup is one of the most unpleasant things that can happen in a home. It's also one where doing the wrong thing, like wading in with a mop, can make people sick. Here's what to do.

Stay out, and why

Raw sewage contains bacteria, viruses and parasites that can cause stomach illness, skin infections and other problems. Under the IICRC S500 restoration standard, sewage is Category 3 water, the most contaminated level. (See our guide to water damage categories for how the levels work.)

Do this right away:

1. Keep people and pets out of the basement. Especially children, older adults, pregnant people and anyone with a weak immune system or breathing problems.
2. Stop using water. Every flush, shower, load of laundry or dishwasher cycle in the house can send more wastewater to the lowest drain. Tell everyone at home.
3. Cut power to the area if the breaker panel is somewhere dry. If you'd have to walk through sewage to reach it, don't. Call the electric utility or an electrician.
4. Turn off HVAC if the furnace or air handler is in the affected area, so it doesn't spread odors and contaminated air through the house.
5. Open windows if you can do it without walking through the water.
6. Photograph from the stairs for your insurance claim.

If you must enter, wear rubber boots, waterproof gloves and eye protection, and wash thoroughly afterward. Don't eat, drink or touch your face while in the area.

Your lateral vs. the municipal main

The next question is where the blockage is, because it decides who fixes it.

Your sewer lateral is the pipe that runs from your house to the public sewer main, usually under your yard to the street. In most Pennsylvania municipalities, the homeowner is responsible for the lateral, sometimes all the way to the main. Check your municipality's or sewer authority's rules.

Common causes of a lateral backup:

• Tree roots growing into joints of older clay or cast-iron pipe
• Grease, wipes and paper products building up
• A collapsed or sagging (bellied) pipe
• A blocked cleanout

The municipal main is the public sewer under the street. Backups from the main are less common but can happen when the main is blocked or overloaded during very heavy rain.

Clues to which one it is:

• Only your house is affected, and the backup gets worse when you run water: likely your lateral. Call a plumber or drain service to clear and camera the line.
• Neighbors are having backups too, or it happens during heavy rain without anyone using water: possibly the main. Call your municipality or sewer authority right away and report it. Ask for a reference number.

Either way, keep notes: when it started, who you called, what they found.

What must be thrown out

Porous materials absorb sewage deep into their fibers. They can't be reliably disinfected and are generally discarded.

Usually thrown out:

• Carpet and carpet pad
• Upholstered furniture
• Mattresses and box springs
• Drywall and insulation the water touched, usually cut out at least a foot or two above the water line
• Cardboard boxes and paper goods
• Stuffed toys, pillows and fabric items that can't be hot-washed
• Food, medicine and cosmetics that were exposed
• Particleboard furniture and cabinet bases

Often salvageable with proper cleaning:

• Hard plastic, glass, metal and ceramic items
• Solid wood furniture, if cleaned and dried promptly
• Concrete floors and stone walls
• Some clothing and washable fabrics, washed hot with detergent (professional cleaning for valuables)

Photograph everything before it goes out, and list it for your claim. Ask your adjuster whether they need to see any items or samples first.

Professional sanitizing

Sewage cleanup isn't a mop-and-bleach job. A professional cleanup typically includes:

1. Containment to keep contamination from spreading to clean areas.
2. Extraction of liquid and solids with pumps and extractors.
3. Removal of porous materials that were affected.
4. Cleaning hard surfaces to remove residue. Disinfectant only works on surfaces that are already clean.
5. Disinfecting with an EPA-registered product appropriate for the job.
6. Drying with dehumidifiers and air movers until moisture readings reach a dry standard.
7. Final check for odor and moisture before rebuild.

Our flood damage cleanup team handles Category 3 water, including sewage backups, with protective equipment and photo documentation for your claim. We serve homes across West Goshen and nearby. See our West Goshen page for local details.

Backwater valves and endorsements

Once the basement is clean, two things can reduce the chance and the cost of a repeat.

Backwater valve

A backwater valve (sometimes called a backflow valve or check valve) is installed on your sewer line and lets wastewater flow out but closes when sewage tries to flow back in. It's most useful when backups come from an overloaded main. Installation usually needs a licensed plumber and may need a permit from your municipality. Ask the plumber about access for maintenance; the valve needs occasional cleaning.

Other prevention steps:

• Have the lateral camera-inspected if you have big trees or an older pipe
• Don't flush wipes, even "flushable" ones
• Keep grease out of the kitchen sink
• Make sure floor drains have working caps or plugs where appropriate

Water backup endorsement

Many standard homeowners policies exclude sewer and drain backup unless you've added a separate endorsement. Pennsylvania's flood insurance guidance notes that sewer and sump backup usually needs one (pa.gov flood insurance). Check the limit: a full sewage cleanup and rebuild in a finished basement can cost far more than a small endorsement covers. Typical basement water cleanup ranges about $750–$4,000 for mitigation, and large contaminated losses can pass $10,000 with rebuild.

FAQ

Can I clean up a small sewage backup myself?

A very small backup on bare concrete can sometimes be cleaned by a careful homeowner with protective gear, cleaning followed by disinfecting, and good drying. If it reached carpet, drywall or a finished area, call a professional.

Is bleach enough to disinfect sewage?

Bleach doesn't work well on dirty surfaces or porous materials. Surfaces must be cleaned first. Never mix bleach with ammonia or other cleaners.

Will homeowners insurance pay for a sewer backup?

Only if your policy includes water backup coverage, in most cases. Ask your agent.

How long until the basement is usable again?

Cleanup and drying often take several days. Rebuild time depends on how much was removed.

Sewage in your basement?

Call (555) 000-0000 for safe sewage cleanup and disinfection. (555) 000-0000 · Get a Free Quote