What a shower pan is
Tile and grout are not waterproof on their own. In a traditional tiled stall shower, a sloped mortar bed sits on top of a waterproof liner, often a sheet membrane, that wraps up the walls a few inches and seals to the drain. Water that soaks through the grout runs along the liner and into weep holes in the drain.
When that liner is punctured, wasn't lapped high enough, or its seal at the drain fails, water escapes sideways into the subfloor, the bottom of the walls and, in a slab home, the concrete under the bathroom. Molded fiberglass or acrylic shower bases work differently and fail differently, usually by cracking.
Signs the pan may be leaking
- Damp or darkened grout at the bottom row of floor tile that never dries out
- Loose, cracked or hollow-sounding floor tiles inside the shower
- Swollen baseboard, door casing or vanity next to the shower
- Water stain or damp carpet in the room on the other side of the shower wall
- A musty smell that cleaning doesn't fix
- Ceiling stain below a second-floor stall shower that appears after showers
How a pan leak is confirmed
The goal is to rule out the valve, walls and drain before blaming the pan.
- Spray the walls only.Run water on the wall tile with the floor kept as dry as possible. A leak now points to the walls, grout or caulk.
- Check the drain.Pour water directly into the drain. A leak now points to the drain connection rather than the pan.
- Flood test.The drain is plugged and the floor is flooded to a set depth, marked and left for hours. A falling water line with no other leak points to the pan.
- Look below or behind.Damp found under or beside the shower during the flood test supports the finding.
Repair or rebuild
Limited repair
- Possible if the leak is at the drain flange or a corner seal
- Some cases can be addressed by resealing at the drain
- Surface coatings are sometimes offered; ask how long they are expected to hold
- Less disruption
Full pan rebuild
- Floor tile and mortar bed come out
- New liner or waterproofing system, sloped to the drain
- Usually the lower wall tile is disturbed too
- Most dependable when the liner itself has failed
What to ask before a pan rebuild
- Which tests did you run, and how did you rule out the walls and drain?
- What waterproofing method will you use, and will it be tested before tile?
- Who does the tile work, and is it in the written price?
- How will you check for damage to the subfloor or framing?
- Does this need a permit and a pan inspection?
Common questions
Can I just regrout to stop a pan leak?
Regrouting can slow water getting in, but if the liner underneath has failed it won't stop the leak. Test first.
How long does a flood test take?
It usually runs for hours so a slow drop in water level is visible. Ask the plumber how long they will run it.
Do fiberglass shower bases have pans?
No. A one-piece base is its own waterproof layer. It leaks when it cracks or when the drain seal fails.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.