Sewage Backup in Your Basement on Long Island: What to Do Now

If sewage is coming up through a floor drain, toilet or shower in your basement, stop using all water in the house, keep everyone out of the affected area, and call a professional cleanup company right away. Sewage is contaminated "black water," and the longer it sits, the more material has to be torn out and the higher the risk of mold.

Basement sewage backups are one of the most common emergency calls on Long Island, especially after heavy rain. Here's what to do in the first hour, what causes it, and how insurance usually treats it.

First steps (do these now)

1. Stop using water. Don't flush toilets, run the dishwasher, washing machine or showers. Every gallon you send down the drain can come back up in the basement.
2. Stay out of the water. Sewage can carry bacteria and viruses. If you must go in, wear rubber boots, gloves and eye protection, and wash thoroughly afterward.
3. Watch for electrical hazards. If water is near outlets, a furnace, a boiler or the electrical panel, don't wade in. Shut off power to the basement at the breaker only if you can reach it safely and dry.
4. Turn off the HVAC if the return vents are in the basement, so you don't pull contaminated air into the rest of the house.
5. Document everything. Take photos and video of the water, the drain it came from, and damaged belongings before anything is moved.
6. Call your insurance company to open a claim, and call a restoration company to begin extraction and cleanup.

What causes sewage backups on Long Island?

• Heavy rain overwhelming the system. Storms can push more water into sewer mains than they can carry, and the lowest drain in the neighborhood (often a basement floor drain) is where it comes out.
• A blocked sewer line from the house. Tree roots, grease, "flushable" wipes and collapsed or bellied pipes in older homes are common culprits. If only your house is affected, the blockage is often in your own line.
• Cesspool or septic problems. Much of Long Island, especially Suffolk County, isn't on public sewers. A full or failing cesspool can back up into the house during wet weather.
• No backwater valve. Homes without a backwater (check) valve have nothing stopping water in the main from flowing back into the basement.

Who is responsible for the sewer line?

It depends on where the blockage is. In many communities the homeowner is responsible for the private sewer line (the "lateral") from the house to the connection with the public main, while the municipality or sewer district is responsible for the main itself. If neighbors are backing up too, the problem may be in the main, so report it to your town or sewer district right away. If you're on a cesspool or septic system, maintenance falls on the homeowner.

Does insurance cover sewage backup?

This is where many Long Island homeowners get surprised:

• Standard homeowners policies usually exclude it. Water that backs up through sewers or drains is a common exclusion.
• A water backup endorsement is what typically covers it. Many insurers sell a "water backup and sump discharge or overflow" rider, often with a separate coverage limit. If you have it, cleanup and damaged property are usually covered up to that limit.
• Flood insurance is different. An NFIP or private flood policy generally covers backup only when it is directly caused by a flood, not by a clogged line on a dry day.
• Document before cleanup. Adjusters want photos, a list of damaged items and the cleanup company's moisture readings and scope of work.

Check your declarations page for a backup endorsement, and ask your agent before assuming you're covered or not covered.

What professional sewage cleanup involves

Sewage cleanup follows a different process than clean-water damage:

1. Containment so contaminated air and debris don't spread to the rest of the house.
2. Extraction of standing sewage with pumps and wet vacuums.
3. Removal of porous materials that touched the water, such as carpet, padding, drywall below the water line, insulation and many furnishings. These generally can't be safely cleaned once contaminated.
4. Cleaning and disinfecting concrete, framing and other non-porous surfaces.
5. Structural drying with dehumidifiers and air movers, verified with moisture readings, so mold doesn't follow.
6. Rebuild once everything is dry and clean.

Doing this fast matters. Wet drywall and wood can begin growing mold within 24 to 48 hours, which turns a cleanup into a bigger remediation job.

How to reduce the chance it happens again

• Have a plumber camera-inspect the sewer line if you've had more than one backup.
• Ask about installing a backwater valve on your main line.
• Keep grease, wipes and paper towels out of the drains.
• Have your cesspool or septic system pumped and inspected on schedule.
• Review your insurance and consider adding a water backup endorsement.

For more on keeping water out of your basement, see our guide to preventing basement flooding.

Need sewage cleanup now?

Aqua-Pro Restoration provides 24/7 emergency sewage and water damage cleanup across Nassau and Suffolk counties, NYC and the surrounding area. Learn more about our biohazard and sewage cleaning and water damage restoration services, or see our Nassau County and Suffolk County service pages.

Call (855) 229-9998 any time, day or night.

Is sewage backup in a basement dangerous?

Yes. Sewage is classified as Category 3 (black) water under the IICRC S500 standard because it can carry bacteria, viruses and parasites. Avoid skin contact, keep children and pets away, and don't run fans or HVAC that can spread contaminated air through the house.

Does homeowners insurance cover sewage backup on Long Island?

Usually only if you bought a water backup or sewer backup endorsement. Most standard homeowners policies exclude water that backs up through sewers or drains. Flood insurance generally covers backup only when it is directly caused by a flood. Check your declarations page or call your agent.

Can I clean up a sewage backup myself?

Small, contained backups from a toilet can sometimes be handled with proper protective gear, but anything that soaks carpet, drywall or insulation should be handled professionally. Porous materials that touched sewage generally have to be removed, not just cleaned, and the area must be disinfected and dried to prevent mold.