Short answer
Water you can hear running or see dripping inside a wall or ceiling, with no fixture in sight, is almost always a pressurized supply line. A drain leaks only while something drains, and a roof leak only shows in rain, but a supply line leaks day and night. Shut off the main water valve and watch the meter. If the dial stops, the leak is on your plumbing, and a plumber locates it and opens the wall to repair that section. If water keeps appearing with the main off, the source is a drain or the roof instead.
Tell a supply leak from a drain or roof leak in 20 minutes
- Find the main water shutoff. It is usually at the meter at the street, or where the line enters the house. Turn it fully off.
- Open a low faucet to drain the pipes, then watch the water meter dial for 10 minutes. A dial that stops means the water is no longer under pressure on your side.
- Listen again at the wall or ceiling. Water that goes quiet when the main is off is a supply line. Water that drips only when you run a sink, shower or toilet is a drain.
- Check the ceiling after the next rain. A drip that only appears in wet weather comes through the roof, not the pipe.
- Dry the wall or ceiling and mark the edge of the wet patch with a pencil. A patch that grows within a day is an active leak that needs opening today.
If the water stops with the main off and the meter dial stays still, you have a supply leak and a plumber opens the wall or ceiling at that spot. If water still appears with the main off, the fault is a drain or the roof, and that is a different repair.
Repair or replace
| Situation | What to do |
|---|---|
| Supply leak confirmed, wall or ceiling closed | Repair. A plumber opens the smallest access, replaces the failed section of pipe, and patches the drywall. |
| Water drips only while a fixture runs | Repair the drain joint. That is a drain leak, not a supply line, and the joint is cut out and remade. |
| Water appears only in rain | Repair the roof above. Fix the water at the roof first, because a plumbing patch under a live roof leak fails. |
| Dripping near a light, outlet or switch | Hire an electrician as well. Water in a live box is a shock and fire risk, so keep that circuit off until it is dry. |
| The same line has frozen or burst before | Replace that run. Repeated bursts on an old line mean the pipe itself is finished. |
What it costs
Runhome contractor estimates for finding and repairing a concealed water leak inside a wall or ceiling ran from $330 to $930 as of October 2026, including the trip, the leak investigation and the drywall patch.
| Option | Range |
|---|---|
| Locate and repair the concealed pipe, patch the drywall | $330 to $930 |
Can I do it myself?
You can do the detective work yourself, but not the repair. Turning off the main water and watching the meter costs nothing and tells a plumber where to start. Once the leak is confirmed on a supply line, hire someone, because opening a finished wall or ceiling, cutting out a pressurized pipe and making a sound joint is a plumber's job. Water that reached a light, an outlet or a switch makes that circuit an electrician's job until it is dry. If you cannot reach or safely turn the main shutoff, stop and call a plumber rather than working around live water.
What a contractor will ask you
Have these ready and you skip the back-and-forth.
- Whether the water is clear like tap water or coloured and smelly. Clear cold water points at a supply line.
- Whether the drip is constant or only when it rains. Constant water is a pipe, weather-linked water is the roof.
- Whether the leak stops with the main water off, and where your main shutoff is.
- How long the water has been running, and whether the wet patch is growing.
- A wide photo of the wet wall or ceiling and the room around it, taken from a few steps back.
- What sits directly above the leak, such as a bathroom, a kitchen or the attic.
Common questions
- I can hear water running inside my wall and I can't see anything.
That is almost always a pressurized supply line leaking behind the wall, and it runs day and night. Shut off the main water and listen again. If the sound stops, a plumber opens the wall at the noise and repairs that section of pipe.
- Does clear cold water dripping from the ceiling mean a pipe or the roof?
Clear water that drips constantly, rain or shine, points at a supply pipe in the ceiling. Water that only shows up in wet weather comes through the roof. Turn off the main water and watch whether the drip stops to settle it.
- Can I just patch the ceiling and paint over it?
No, not while the leak is live. A patch under an active leak fails within weeks and hides the damage above it. Fix the source first, let the area dry, and then repair the drywall.
- Is a hidden water leak an emergency?
Yes if it is near wiring, if the wet patch is growing fast, or if you cannot shut the water off. Cut power to any circuit near the wet area and call a plumber the same day.
- How do I find a leak I can't see?
Shut off the main water and watch the meter dial for 10 minutes. A dial that still moves means pressure is escaping on your side of the meter. A plumber then uses the meter, sound and moisture readings to pin the leak to one spot.