Water Leaking From the Ceiling: What to Do First

Water leaking from the ceiling: what to do first

Short answer

Protect people and the electrical system first: keep away from light fixtures that are wet, and turn off power to that area if water is near them. Then decide if it's plumbing or the roof. If it drips when no one is using water and it isn't raining, close the main water valve. Under a bathroom, the usual sources are a toilet seal, a shower pan or drain, or a supply line.

Right now

Stay clear of wet light fixtures
Turn off the circuit at the panel if water is near lights or outlets and you can reach the panel from a dry spot.
Relieve a bulging ceiling
If the drywall is sagging with water, put a bucket under it and pierce the lowest point with a screwdriver to drain it in a controlled way. A ceiling full of water can collapse.
Shut off the water if it's plumbing
If the drip continues with no water in use, close the main shutoff.

Plumbing or roof?

If Drips only during or after rain: Roof, flashing or gutters. A roofer, not a plumber, unless a vent pipe boot is leaking.
If Drips when the shower or tub upstairs is used: Shower pan, drain gasket, tub overflow or grout. Test by running each fixture separately.
If Drips after the toilet upstairs is flushed: Toilet wax ring or the tank-to-bowl gasket.
If Drips all the time, with or without use: A pressurized supply line. Close the main valve and call.
If Below an attic water heater or AC unit: Heater leak or a clogged condensate line. See water heater leaking.

Testing upstairs fixtures one at a time

Supply test
With nothing running, does it drip? If yes, it's a supply line, so stop and call.
Drain test
Run the sink, then the tub, then the shower, each for a few minutes, waiting between. Note which one starts the drip.
Toilet test
Flush several times, then check below.

Why fast drying matters

Wet drywall, insulation and framing can grow mold within a day or two in warm conditions. Once the leak is fixed, the ceiling usually needs to be opened so the cavity can dry properly. Photograph everything before cleanup for insurance.

The usual sources under a bathroom

Toilet wax ring: stain directly below the toilet, worse after flushing.
Shower pan or drain gasket: stain below the shower, only after showers.
Tub overflow gasket: leaks only when the tub is filled high.
Failed grout or caulk: water runs behind tile during showers; slow and intermittent.
Supply line or valve: constant drip regardless of use.

Call a plumber now if

The drip continues with no water in use.
The ceiling is sagging or near electrical fixtures.
You traced it to a shower, toilet or drain upstairs.