Sewage cleanup in NYC is most often needed after heavy rain, not after a broken pipe. When a storm drops more water than the city’s sewers can carry, the water backs up and comes out wherever the building’s lowest connection is: a basement floor drain, a toilet, a shower or a laundry sink. This page explains why it happens, what not to do, and how a proper cleanup goes.
Water line
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Why sewers back up into New York basements
The Department of Environmental Protection describes sewer backups as what happens when heavy rain exceeds the capacity of the pipes, causing overflows from manholes, catch basins and the sewer connections in basements. The numbers from Hurricane Ida show the scale: NYC Health reports that rain fell at a record 3.5 inches an hour in some areas, while the city’s sewers can carry 1.75 inches an hour.
On the shore there is a second cause. DEP notes that coastal flooding, high tide plus storm surge, can send tidal water back into the sewer system. So a basement in a low-lying waterfront neighborhood can see water come up through its drain even without much rain.
There is also a cause inside many homes. DEP makes it mandatory for homeowners to disconnect their downspouts from the sanitary sewer, because those connections can overwhelm the sewer with rainwater and cause sewer backups in basements. Non-compliance may result in fines.
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Sewage is Category 3 water
There is no debate about the category of sewer water. The ANSI/IICRC S500 water damage standard defines Category 3 as “grossly contaminated” water that “can contain pathogenic, toxigenic, or other harmful agents.” Its first examples are sewage and “wasteline backflows that originate from beyond any trap regardless of visible content or color.” In plain words: water that came back up from the sewer is Category 3 even if it looks clear.
For Category 2 and 3 water, the standard says remediation should occur before restorative drying, and restorers shall use contamination controls and appropriate worker protection. That is the difference between sewage cleanup and simply drying a wet floor: the contamination is dealt with first, and only then is the space dried.
The EPA on sewage
“If the water and/or mold damage was caused by sewage or other contaminated water, then call in a professional who has experience cleaning and fixing buildings damaged by contaminated water.”
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What not to do
- Do not walk through it barefoot or in sneakers. The CDC links floodwater exposure to wound infections, skin rash, gastrointestinal illness and tetanus, and advises rubber boots, rubber gloves and goggles if you must enter it.
- Do not touch switches or plugs while standing in it. The CDC says never turn power on or off, or use an electric tool or appliance, while standing in water.
- Do not flush, run the washer or drain sinks while the sewer is backing up. Water you send down can come straight back up in the basement.
- Do not mix cleaners. The EPA warns never to mix cleaning products or add bleach to other chemicals, and says bleach is not recommended as a routine practice in mold cleanup.
- Do not run the heating or cooling system if it may be contaminated. The EPA says not to run an HVAC system you know or suspect is contaminated with mold.
- Do not throw anything away before photographing it. You may need the photos later.
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The sewage cleanup order
A careful sewage cleanup follows the same order whether it is a few inches across a laundry room or a full cellar.
- Make it safe. Power to the area off from a dry place, or by an electrician. Children and pets kept away. Windows opened if there are any.
- Wait for the backup to stop. While the street sewer is surcharged, water keeps coming. Pumping out against it only moves the water around.
- Contain the area. The S500 names containment barriers among its contamination controls: professionals separate the affected room from the rest of the building so the cleanup does not spread contamination upstairs.
- Remove the water and solids with pumps and extraction, with workers in protective gear.
- Remove porous materials the sewage reached: carpet and pad, drywall and insulation, cardboard, upholstered items. The CDC says to discard drywall and insulation contaminated with sewage or floodwater, and to throw away what cannot be cleaned or dried quickly.
- Clean and disinfect hard surfaces: concrete, tile, metal pipes and fixtures.
- Dry with air movers and dehumidifiers. The EPA’s guidance is to dry water-damaged areas within 24 to 48 hours to prevent mold.
- Check the result with moisture readings before anything is rebuilt.
Wash clothing that touched sewage in hot water and detergent before wearing it again, as the CDC advises. The flood cleanup guide covers drying and documentation in more detail.
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Plumber, restorer or the city?
Three different people may be involved after a sewer backup, and it helps to know which one does what.
| Problem | Who usually handles it |
|---|---|
| Sewage in the basement, wet walls and floors | A restoration provider: cleanup, removal, drying |
| A broken or blocked sewer line on your property, a backwater valve | A plumber. FloodHelpNY says a licensed plumber or engineer can tell you which valve, if any, suits your home |
| Flooding manholes, a clogged catch basin, water on the street or sidewalk | The city: report it to 311 |
| A rental apartment | Tell the landlord or managing agent in writing first |
DEP cleans and maintains about 150,000 catch basins across the city and asks residents to report a clogged one to 311. NYC311 also takes reports of manhole flooding and of water leaking on a street or sidewalk.
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Stopping the next backup
A backwater valve on the building’s sewer line is designed to let sewage out and stop it coming back in. FloodHelpNY lists the common types: gate valves, ball valves and flapper valves, also called check valves or duckbill valves. It also lists the communities in its Residential Backwater Valve Installation Program: Lower Manhattan, Rockaway East, Southeast Brooklyn Waterfront, Gravesend and Bensonhurst, Howard Beach, Gerritsen Beach and Sheepshead Bay, and the Southern Brooklyn Peninsula. Whether that program is taking applications now is something to check with FloodHelpNY directly.
Disconnecting downspouts is the other step, and DEP says it is mandatory: send the water at least 6 feet away from the foundation instead of into the sewer. DEP’s “Rainfall Ready: A Homeowner’s Guide,” published in 12 languages, gathers more tips on protecting a home from flooding and sewer backups. The basement waterproofing page covers all of these together.
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Sewage cleanup across the boroughs
The causes change a little from one part of the city to another. In Manhattan, Brooklyn and the Bronx, backups often follow cloudbursts, when rain outruns the sewers under streets packed with row houses and apartment buildings. On the Staten Island and south Brooklyn shores, DEP’s coastal flooding adds tidal water to the mix during high tides and storms, which is why several of the communities on FloodHelpNY’s backwater valve list sit on the water. Whatever the borough, the cleanup is the same Category 3 job, and the form takes requests from all five.
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Insurance and sewer backups
FloodSmart, the National Flood Insurance Program’s site, says that damage caused by a sewer backup is covered by flood insurance if the backup is a direct result of flooding. For a backup with another cause, this site cannot say what any policy covers. Check your own policy or agent before the cleanup starts, and keep the photos. The flood insurance basics page has the general rules.
If the backup came with a flooded basement or basement apartment, read basement flooding in NYC for the safety steps first.
Sewer water in the basement? Send the form with your borough and what happened, and an independent local sewage cleanup provider can contact you.
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Questions people ask
How do you clean up sewage?
Safely and in order: power off from a dry place, wait for the backup to stop, contain the area, remove water and solids, discard soaked porous materials, clean and disinfect hard surfaces, then dry. The IICRC S500 says contamination is dealt with before drying, and the EPA advises a professional for sewage.
Is a sewer backup an emergency?
Treat it as one. Sewage is Category 3 water under the IICRC S500 standard, and the CDC links contact with floodwater to infections and illness. Stop using water in the building, keep people away and get the cleanup started.
Why does sewage come up through my basement drain when it rains?
Heavy rain beyond the sewers’ capacity overflows through basement sewer connections, DEP explains. Downspouts connected to the sanitary sewer add to it, which is why DEP makes disconnecting them mandatory.
Is clear water from a floor drain still sewage?
Yes. The S500 standard counts wasteline backflows that originate from beyond any trap as Category 3 regardless of visible content or color.
Who do I call about a flooding manhole?
311. NYC311 takes reports of manhole flooding and of water leaks on streets and sidewalks, and DEP asks residents to report clogged catch basins to 311.
Does insurance cover a sewer backup?
It depends on the cause and the policy. FloodSmart says flood insurance covers sewer backup damage when the backup is a direct result of flooding. Check your own policy or agent.
NowWater in the building?
Tell us where and what happened, and an independent local provider can contact you.