A leaking shower pan lets water through the floor of the shower into the subfloor, often showing up as a stain on the ceiling below, loose tile, or water at the base of the wall or toilet next to the shower. Test by plugging the drain and flooding the shower floor with about 2 inches of water. If the level drops or a stain appears below, the pan or drain is leaking.
A shower sends gallons of water onto the floor every day, and the only thing between that water and your subfloor is the shower pan: the liner or molded base under the tile, sealed to the drain. When it fails, the water goes down instead of out the drain. It’s one of the most common hidden leaks in a bathroom, and one of the most commonly misdiagnosed. Here’s how to recognize it and test for it.
Signs of a shower pan leak
- A stain on the ceiling below the shower, often growing after showers
- Loose, cracked or hollow-sounding floor tile in the shower
- Grout that stays dark long after the shower dries
- Water or damage outside the shower: at the base of the wall, under the vanity, or around the toilet
- Swollen baseboard or door trim next to the shower
- A musty smell or mold at the shower curb
- In a slab home, damp flooring in the next room
Pan, drain, grout, door or valve?
Water can escape a shower in several ways. Test one thing at a time:
| Test | What it checks | If it leaks |
|---|---|---|
| Spray only the walls for 10–15 minutes | Wall grout, caulk, niches | Wall tile or caulk |
| Spray only the door or curtain area | Door seals, curb, splash | Door sweep or curb |
| Flood test the floor (below) | Pan liner and drain | Shower pan or drain |
| Run the shower into a bucket | Valve, showerhead arm | Valve or supply |
| Meter test with everything off | Pressurized supply lines | A constant supply leak |
How to flood test a shower pan
This is the same basic test plumbing inspectors use on new showers.
- Plug the drain watertight (a test plug or a sturdy balloon-type plug).
- If the curb is low, build a temporary dam with plumber’s putty or tape so the water can’t spill out.
- Fill the shower floor with about 2 inches of water.
- Mark the water level with tape.
- Wait several hours, ideally 24, checking the ceiling below and the floor around the shower.
The Uniform Plumbing Code calls for a 2-inch, 24-hour test on new shower liners; the International Residential Code allows a shorter one. For diagnosis at home, the longer you wait, the more certain the result. A dropping water level, with no evaporation to blame, or a new stain below means the pan or drain is leaking.
The shower valve: a different kind of leak
A leaking shower valve or supply pipe behind the wall acts differently:
- It leaks when the shower is on, or all the time if the supply line itself leaks
- Water shows up in the wall behind the valve, or on the other side of that wall
- A meter test with everything off catches a constant supply leak
See how to find a water leak inside a wall for tracing it.
Repair options
| Problem | Typical fix |
|---|---|
| Leak at the drain connection | Reseal or replace the drain assembly; sometimes possible from below |
| Grout or tile letting water through | Regrout and seal, if the liner underneath is intact |
| Cracked acrylic or fiberglass base | Replace the base |
| Failed liner under a tile floor | Remove the tile floor, replace the liner, retile |
| Valve or supply leak | Repair or replace the valve through an access panel or small wall opening |
Before any demolition, the wet area should be mapped. Subfloor and framing under a long-leaking shower can be soaked well beyond the shower itself.
How professionals pinpoint it
With hidden water leak detection, we:
- Flood test the pan and drain, and test the valve and supply separately
- Use a thermal camera to show the wet pattern on the ceiling below or the walls around the shower
- Map moisture in the subfloor, walls and ceiling, so the repair covers everything that’s wet and nothing that isn’t
- Provide photos and readings for your insurer
A thermal imaging inspection is also useful before buying a home with a tiled shower. If the leak shows up as a ceiling stain, see water leaking from the ceiling. If water is appearing at the toilet next to the shower, see toilet leaking at the base.
Get it tested
We test showers, tubs and the pipes behind them across Bargersville and Johnson County, including Greenwood, Center Grove and Franklin. If there’s a stain below your shower, call us before you start tearing out tile.
Still can’t find it?
Our hidden water leak detection pinpoints the leak without tearing things up, so the repair starts in the right spot.
Frequently asked questions
How do I know if my shower pan is leaking?
Common signs are a stain on the ceiling below the shower, loose or cracked floor tile, grout that stays dark, a musty smell, and water or damage on the floor outside the shower, especially near the toilet or vanity.
How do you test a shower pan for leaks?
Plug the drain, build a temporary dam at the curb if needed, and fill the shower floor with about 2 inches of water. Mark the level and wait. A dropping level or a new stain below means the pan or drain is leaking.
Can a leaking shower pan be repaired without tearing out the shower?
Sometimes. Leaks at the drain or through grout can sometimes be fixed without removing the floor. A failed liner under a tile floor usually means removing and rebuilding the shower floor.
Is it the shower pan or the shower valve?
A pan or drain leaks only when water is on the shower floor. A valve or supply line leaks when the shower is running or all the time, and a meter test catches a constant supply leak. Testing each part separately tells them apart.