Finding a leak in a Manhattan apartment: where it's coming from and who fixes it
A brown stain on the ceiling, a bubbling wall or a damp floor could come from your plumbing, the apartment upstairs, a building riser, an AC unit or the façade. Finding the source is the first job, because it decides who pays and who fixes it.
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Emergency? Gas smell, CO alarm, fire, sparking or flooding: get to safety and call 911 first.
Common leak sources in Manhattan buildings
- Apartment above: tub and shower pans, toilet seals, washing machines and dishwashers.
- Building risers and branch lines inside walls, shared by several apartments.
- AC units: condensate from window, through-wall or fan coil units.
- Exterior: windows, parapets, roofs and façade cracks, which usually show up after rain.
- Your own fixtures: supply lines, valves and drains.
Quick checks
- Note when it appears: after rain points outside; after someone upstairs showers points to their bathroom; constant suggests a supply line.
- Photograph and date the damage every day.
- Check your own supply lines and under-sink valves for drips. See leak under the sink.
- Check for silent toilet leaks with a few drops of food coloring in the tank.
Who to call first
In a co-op, condo or rental building, tell the super or managing agent right away. They can get into the apartment above, shut a riser, and bring in the building's plumber. If the source is your own fixture, hire a NYC Licensed Master Plumber; leak detection pros may use moisture meters, thermal cameras and pressure tests to pinpoint it without opening many walls.
After the leak: mold and insurance
Wet drywall and insulation can grow mold within days, so dry things out quickly. In rentals, leaks and mold are the owner's responsibility to fix; HPD can inspect and issue violations if they aren't. Larger buildings (10+ units) must use licensed mold assessors and remediators for mold over 10 square feet. Owners should notify their insurer early; co-op and condo policies often depend on where the leak started.
Questions
Who pays for a leak from the apartment upstairs?
It depends on the source and your building's documents. Usually the party responsible for the leaking fixture or pipe. Notify management and your insurer right away.
How do plumbers find hidden leaks?
With moisture meters, thermal cameras, pressure tests and sometimes small inspection openings. Ask what method they'll use and what opening walls might involve.
Can a leak cause mold?
Yes. Dry wet materials quickly. In rentals, report leaks and mold to the landlord and to 311 if they aren't fixed.
Sources
Rules and phone numbers can change. Check the official source before relying on them.
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Published 2026-10-20 · Updated 2026-10-20
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