Leaks and Mold in New York City Apartments

Why NYC Apartments Leak

New York City apartments are stacked on top of each other and share plumbing, heating pipes, roofs and walls. A problem in one unit often shows up in another. Much of the housing is old, so pipes, valves and seals are often decades past their design life.

• The unit above. An overflowing tub, a failed toilet seal or a burst supply line upstairs often comes through your ceiling first.
• Risers. The vertical pipes that carry water, waste and steam run through every floor. When a riser leaks inside a wall, several apartments can be affected.
• Steam heat. Radiators, their valves and air vents can spit or leak water during the heating season.
• Roofs, parapets and facades. Top floor units and units under old brick walls see leaks in wind driven rain.
• Windows and air conditioners. Poorly sealed window units and sleeves let rain run into walls.
• Basements and garden units. Heavy rain can flood them from outside and from backed up sewers.

Because the source is often outside your apartment, you usually cannot fix it yourself. Your job is to protect your space, get the problem on record quickly and make sure the right person fixes both the leak and any damage it caused.

When Water Comes From Upstairs

Act fast, because the longer water runs, the more ceilings and walls it soaks.

1. Protect yourself. If water is near a light fixture or outlet, turn off that room’s breaker if you can do it from a dry spot. Stay out from under a sagging ceiling.
2. Catch the water. Put buckets under drips, move furniture and electronics, and cover what you cannot move with plastic.
3. Go upstairs. Knock on the door above. Often a neighbor does not know their tub or toilet is overflowing.
4. Call the super or management. If nobody answers upstairs, the super can enter in an emergency and can shut off the riser for that line.
5. Document everything. Take dated photos and video of the ceiling, the water and damaged items.
6. Put it in writing. Send an email or letter to the landlord or managing agent the same day. Keep a copy.

After the leak stops, the ceiling and wall cavity need to dry fully before they are painted or patched. Ask the building what drying they plan. Plaster and drywall that stay wet for more than a couple of days can grow mold on the back side. If the building paints over a wet stain, it will come back, and so may the mold.

Your own belongings are usually covered by your renters or unit owner policy, not by the building’s policy. Call your insurer soon.

Steam Radiators, Valves and Old Risers

Many older buildings use one pipe steam heat. Steam rises through a riser into each radiator, and condensed water flows back down the same pipe. A few common problems cause leaks and noise.

• Spitting air vent. The small vent on the side of the radiator lets air out. If it spits water or steam, the radiator may be pitched wrong, so water cannot drain back, or the vent has failed.
• Leaking supply valve. Water around the valve at the base can come from worn packing around the stem. On one pipe systems, the valve should be fully open or fully closed, never halfway.
• Banging pipes. Knocking often means water is trapped in a pipe or radiator that is not sloped right.
• Hidden riser leaks. Stains or peeling paint on the wall or ceiling next to a heating pipe can mean the riser is leaking inside the wall.

Do not remove vents or open valves while the heat is on. Put a pan under a drip, move rugs and wood away, and report it to the super. Radiator repairs are the building’s job in most rentals and usually in co-ops and condos too.

The legal heating season in NYC runs October 1 to May 31. During the day, apartments must be at least 68 degrees Fahrenheit when it is below 55 degrees outside, and at night at least 62 degrees. Leaks do not excuse a lack of heat.

Who Handles What

Responsibility depends on how you hold your home and what your documents say. The table shows the typical split, but your lease, proprietary lease or bylaws control.

When a leak starts in one unit and damages another, the question of who pays often goes to insurance. Renters should carry renters insurance. Co-op and condo owners should carry a unit owner policy that covers their improvements and liability to neighbors.

Get the answers in writing. Ask management which pipes are the building’s and which are yours before a repair starts. If a contractor you hire must open a wall that holds a riser, the building will usually require approval, proof of insurance and a licensed plumber.

Mold and Local Law 55

Local Law 55 of 2018, sometimes called the Asthma Free Housing Act, applies to most apartment buildings with three or more units. Under it, landlords must take steps to keep apartments free of indoor allergens, including mold and pests.

• Inspect apartments for these conditions every year and when a tenant complains.
• Fix mold and the moisture problem causing it, not just the visible spot.
• Use safe work practices, such as containing the area and cleaning with soap and water, and clean up dust and debris after.
• Give tenants information about these duties with their lease.

Size matters. New York State requires a licensed mold assessor and a separate licensed remediator for mold jobs over 10 square feet, and city rules require licensed professionals for larger mold jobs in larger buildings. The assessor writes a plan and checks the work after, and the remediator does the removal. They cannot be the same company on one job.

For small spots under 10 square feet, a landlord’s staff can usually do the work with safe practices. As a tenant you can wipe a few square inches on bathroom caulk with soap and water, but do not paint over or bleach large patches. That hides the problem and can remove evidence you need. Report it in writing and let the building fix both the mold and the leak.

Reporting a Problem and Calling 311

Start with the super and follow up in writing to the landlord or managing agent. Keep a simple log with dates, who you spoke to and photos. Many problems are fixed at this step.

If the landlord does not act in a reasonable time, call 311 or file online. Complaints about leaks, mold, no heat or no hot water in rental buildings go to the Department of Housing Preservation and Development, known as HPD. An inspector may visit and can issue a violation that the owner must correct. Write down your complaint number and follow up.

• Be home or arrange access for the inspection.
• Show the inspector every affected spot, not just the worst one.
• Look up the building’s open violations and complaints on HPD’s public online system.

New York law protects tenants from retaliation for good faith complaints to the landlord or a government agency. If problems persist, tenants can bring a case in Housing Court asking for repairs, and many tenants use free legal help to do it. Tenants in rent stabilized apartments may also be able to file a complaint with the state housing agency for a decrease in services.

Co-op and condo owners generally handle disputes through the board and managing agent, and through their documents, rather than HPD.

Basement and Garden Apartments in Heavy Rain

Short, intense rainstorms can overwhelm NYC sewers in minutes. Water then rises through floor drains, toilets and tubs in the lowest units, or pours in through doors, window wells and stairwells. People died in flooded basement apartments during the remnants of Hurricane Ida in September 2021. Take flash flood warnings seriously if you live below street level.

• Sign up for Notify NYC alerts.
• Know two ways out and keep a light and shoes by the bed.
• When a flash flood warning is issued, move to a higher floor or leave before water arrives. Do not stay to save belongings.
• Keep valuables, documents and electronics off the floor all the time.
• Put a battery water alarm near the lowest drain.
• Report clogged street catch basins to 311 before storm season.

Water that backs up through drains is sewage. Do not wade in it barefoot, keep kids and pets out, and leave cleanup of anything more than a small amount to professionals. Soaked drywall, carpet and upholstered furniture that sewage touched usually must be thrown away.

Backwater Valves and Sewer Backup

A backwater valve is a one way valve on the building’s sewer line. Waste flows out normally, but when the city sewer backs up, a flap closes and keeps sewage from coming up into the lowest drains. The city’s Department of Environmental Protection encourages owners of buildings with fixtures below street level to consider one.

In NYC, property owners are generally responsible for the sewer line from the building to the city main, including backups caused by that line. Installing a backwater valve is plumbing work that must be done by a licensed master plumber with the right permits.

• Have the valve inspected and cleaned on a schedule, since debris can keep the flap from sealing.
• While the valve is closed during a backup, water used inside the building has nowhere to go. Limit water use until the storm passes.
• Do not pour grease or wipes down drains. They clog the building line and the city sewer.

Standard policies often exclude sewer backup unless you add a specific endorsement, and flood damage needs a separate flood policy. Ask your agent about both if you own a building or a unit below grade. Renters in basement units should ask their landlord whether the building has a backwater valve and when it was last serviced.

Step by Step

1. Protect People and Power

   Keep everyone out from under a sagging ceiling. If water is near a light or outlet, turn off that room’s breaker from a dry spot.

2. Catch and Contain the Water

   Put buckets under drips, move furniture and electronics away, and cover what you cannot move with plastic.

3. Find the Source

   Knock on the door above and call the super. Ask them to shut off the riser for that line if the leak does not stop.

4. Document the Damage

   Take dated photos and video of the ceiling, walls, floor and damaged belongings before cleanup.

5. Report in Writing

   Email or write to the landlord or managing agent the same day, describing the leak, the date and the damage. Keep a copy.

6. Watch for Drying and Mold

   Check the ceiling and walls with a moisture meter over the next week. Ask the building not to paint until readings match a dry wall.

7. Escalate to 311

   If a rental landlord does not repair the leak or mold in a reasonable time, call 311 or file online and keep the complaint number.

Mistakes That Make It Worse

• Only telling the super in passing. Without a written record, it is hard to show when the building knew.
• Painting over a water stain or bleaching a large mold patch. It hides the cause and your evidence.
• Assuming the building’s insurance covers your belongings. It usually does not.
• Staying in a basement apartment during a flash flood warning to move things.

Where You Live Matters