How an in-wall leak shows up
Water that escapes inside a wall follows the pipe, then spreads into the drywall, insulation and framing. By the time you see a stain, the damage behind it is usually larger. In a two-story house, the ceiling below a bathroom is a common place for these stains. This guide covers leaks inside walls and ceilings. If your signs are on a floor or in the yard, see slab leaks or finding hidden water leaks in Greer.
Warning signs
- A brown or yellow stain on a wall or ceiling
- Paint that bubbles or peels
- Drywall that feels soft or cold
- A musty smell with no visible source
- The sound of dripping or hissing in the wall
- Warping around baseboards or cabinets
- Higher water bills with no visible leak
Typical causes
Supply lines can fail at joints. Drain pipes can crack or lose their seal. A shower valve behind the wall may leak at its connections. Freeze damage is rare but possible in a cold spell. Old plumbing, such as galvanized steel, corrodes from inside. Nail or screw punctures are a quiet cause: a picture hook driven through a pipe can start a slow leak.
What to do first
Turn off the water to the fixture that seems related, or shut off the main valve if you are not sure. Place a bucket under any drip. Take photos. Do not cut into the wall yourself, since you may hit electrical wiring. Mark the edge of the stain with a pencil and the date, so the provider can see whether it is growing.
How providers find it
- A moisture meter maps damp areas on the wall surface.
- A thermal camera shows temperature differences that suggest wet material.
- Acoustic tools listen to the pipe.
- A pressure test isolates the suspected line.
- An inspection camera may be used through a small access hole if needed.
After detection
The provider marks where the pipe needs to be accessed. The opening is usually a small cut in drywall. Wet insulation and drywall should be dried or replaced to prevent mold. Ask whether the company handles drywall repair or only plumbing, and get a price for each.
Frequently asked questions
Can a leak in a wall cause mold?
Yes. Persistent moisture can lead to mold in a couple of days, so dry the area promptly.
Do they cut the wall to find the leak?
Not at first. Meters and cameras narrow it down. A small opening is made only where the leak is confirmed.
Is a drain leak different from a supply leak?
Yes. A supply leak is under pressure and constant. A drain leak shows up mainly when water is used.
What if the stain is old and dry?
It may be an old leak. A moisture reading can tell whether it is still active.