How to Tell If Your Shower Pan Is Leaking — and What the Fix Involves

What are the signs of a leaking shower pan?

Water where it should not be, on the far side of the shower: a stain on the ceiling below, a musty smell, a swollen baseboard or loose flooring beside the curb. The shower itself usually looks fine, because the leak is underneath the tile.

Housing specialists at the University of Georgia Extension tell homeowners to check for plumbing leaks around tubs and showers, and to look for discoloration, sagging, bowing or wet spots on ceilings and walls and for a musty, earthy odor [4]. The EPA describes the case that is easy to miss: a room that smells musty with no visible source can have mold growing out of sight — on the back of drywall, under carpet and pad, inside walls around leaking pipes [5]. Water escaping from under a shower floor is exactly that kind of hidden water.

None of these signs proves the pan on its own. The same symptoms can come from the shower valve, the drain pipe or a gap in the walls, which is why the next step is a test, not demolition.

• A stain, sagging or wet spot on the ceiling below [4], especially one that grows after showers
• A musty smell in the bathroom, a closet next to it or the room below, with no visible source [5]
• Baseboard, door casing or flooring swelling outside the curb or on the other side of the shower wall
• Floor tiles that crack, move or sound hollow, or a curb that flexes underfoot
• Grout near the drain that stays dark long after a shower — the bed under the tile is holding water

Why is there a water stain on the ceiling below my shower?

Because water from that bathroom is reaching the ceiling — and the shower pan is only one way it can. The others are the supply pipes to the shower valve, the drain pipe under the shower, gaps in the caulk or grout on the walls, and water getting past the door or over the curb.

Timing narrows it down. Supply pipes are under pressure all the time, so a leak in them keeps going whether anyone showers or not. The EPA’s simple check is to read the water meter before and after a two-hour period when no water is being used; if the meter moves at all, there is probably a leak [6]. A pan, a drain or a wall leaks only when the shower runs, so that stain grows after showers and not between them.

Water that gets past a liner soaks through the mortar bed and can run along the framing before it shows. In our experience the stain is not always directly under the drain, and it can appear well after the shower that caused it — so a stain in the wrong place does not rule the pan out.

Where does a shower pan usually leak?

Where the liner is cut, folded, fastened or joined to the drain. An unbroken sheet does not leak; the details do. These are the four places we check, numbered the same way here and in the drawing after them.

1 · At the drain. The liner is joined to the drain twice. Dallas Specialty’s instructions bond it to the top of the drain body — with bonding fluid on a PVC drain, silicone on metal or plastic — and then clamp it under a ring bolted down over it [1]. A liner that was only clamped, or a ring never pulled down evenly, lets water slip under the ring and down beside the pipe. The weep holes in the drain body must stay clear of liner material and sealant, and Oatey puts pea gravel over them so the mortar does not bury them [3]; blocked, they leave the bed saturated.

2 · At a corner or the curb. Every inside corner is a fold. Both liner makers we cite fold the corners rather than cut them — Dallas Specialty with a “pig ear” fold, Oatey with the fold glued shut — and at the curb, where the sheet is cut along the door opening, both bond on pre-formed dam corners [1][2]. A corner cut to make it lie flat, or a dam corner never bonded, is a gap in the one layer that keeps the water in.

3 · Through a fastener hole. The liner is held up by nails or staples, and every one is a hole. Oatey staples only in the top half inch of the liner and again on the outside of the curb; Dallas Specialty nails half an inch from the upper edge and fastens the curb along its front, outside the shower [1][2]. The Florida code sets its own limit for fasteners near the threshold; it is on our page about what is under a shower floor [7]. A fastener driven low — when the liner goes in, or later when a door frame, glass panel or curb cap is fixed — is a hole below the water line.

4 · A cracked tile or mortar bed. Often blamed, often not the leak. Tile and the bed under it are expected to pass some water; the liner is what stops it. A crack lets more water reach the liner, and if the liner is whole that water runs to the weep holes and down the drain. A crack still matters — a floor that moves can stress the liner and the drain joint, and a bed that stays wet smells — but the crack alone does not prove the pan has failed.

How do you test a shower pan for leaks?

Plug the drain, fill the shower floor with water, mark the level and watch it — after the other possible sources have been ruled out, so the test answers one question. That is how the makers test a new pan: Oatey’s drain instructions fill to just below the top of the curb [3], and its liner guide counts it a pass when the level has not dropped, the area around is dry and no water comes through the ceiling below [2].

How long to wait: there is no published time for a finished, tiled floor. The makers’ tests for a new pan, before any mortar, run from at least two hours in Oatey’s liner guide and at least four hours in its drain instructions to at least 24 hours in Dallas Specialty’s [1][2][3]. A tiled floor also soaks some water into the grout and bed before the level settles, so a small first drop is not a verdict; water outside the shower or below it is.

On a finished shower we work from the outside in, one source at a time:

• Supply pipes. All water off, the meter read before and after a two-hour period with nothing running. If it moves, the leak is in pressurized pipe, not the pan [6].
• Drain line. Water poured straight into the drain without wetting the floor. If the stain or drip answers that, the drain pipe or its joint below is the suspect.
• Walls, door and curb. Each wetted on its own, with the floor kept as dry as possible.
• The pan. Drain plugged, floor flooded, level marked. The plug has to seal below the weep holes — otherwise water that soaks through the grout drains out through them and a sound pan looks like it leaks.

Can a shower pan be repaired without removing the tile?

Not if the liner itself has failed. It lies under a reinforced mortar bed — at least 1½ inches of it in Oatey’s drain instructions — with the tile set on top [3], so the only way to reach a hole, a bad fold or a loose drain joint is to take up the tile and the bed above it.

What can be fixed from above is anything the test places above the liner: a gap in caulk or grout on the walls, a door that throws water over the curb, a leaking valve trim. Those are real repairs, and they are the reason we test before we recommend opening anything.

What does not work is treating a failed pan from the top. Re-grouting, sealing the grout or coating the floor can slow the water reaching the liner, but none of it reaches the liner, and the drain joint and weep holes stay buried under the bed. When the test points at the pan, the honest answer is a new pan.

What does replacing a shower pan involve?

Taking the shower floor up to the base, building a new sloped base, liner and mortar bed, testing the liner with water before anything covers it, and tiling again. Because the liner turns up the walls — at least 6 inches above the finished floor in Dallas Specialty’s instructions [1] — the lowest wall tile comes off with the floor.

The photographs below, from our own jobs in Belleair Beach and South Pasadena, show the stage nobody sees again: 40-mil PVC liner wrapped over the curb, pre-formed dam corners where the curb meets the wall, and the drain in the middle of the pan. In order, the work goes like this:

• Floor tile, mortar bed and the old liner removed, with the lowest wall tile where the liner turns up
• Framing, subfloor or slab edge opened up and dried; anything rotten or moldy replaced before the new pan goes in
• The drain body checked — kept if it is sound and seals, replaced if it is not
• A new pre-slope under the liner, a quarter inch per foot toward the drain, up to but not over the drain base [3]
• The new liner: corners folded or pre-formed, dam corners bonded at the curb, fasteners only at the top edge and outside the curb, bonded and clamped at the drain, weep holes clear [1][2][3]
• A flood test before any mortar or tile — our pans are flood-tested before tile
• Pea gravel over the weep holes, the reinforced mortar bed, then tile [3]

Can I keep using a shower with a leaking pan?

Better not, once you suspect it. Every shower puts more water into wood, drywall or the slab edge, and the EPA’s advice is to fix plumbing leaks as soon as possible and to dry water-damaged areas and items within 24–48 hours to prevent mold growth [5]. Use another shower until the leak has been tested.

It is rarely an emergency in the way a burst pipe is, because a pan only takes on water when the shower runs. If water is coming through a ceiling light, or a ceiling is sagging, treat it as urgent. Kate, our AI voice assistant, answers the phone 24/7; our crews work Monday to Friday, 8am to 6pm.

What this means in Pinellas and across Tampa Bay

In a single-story house on a slab there is no ceiling under the shower to stain. Water that gets past a liner goes into the slab edge and the bottom of the wall framing, so the first signs are low: a baseboard swelling outside the curb, a door casing going soft, flooring lifting in the next room, a closet that smells. In a two-story house or a condo, the ceiling below usually shows it first.

We install shower pan liners on bathroom jobs across Pinellas — the photographs on this page are from Indian Shores, Belleair Beach and South Pasadena — and our pans are flood-tested before tile. When a test shows the leak is somewhere else, we fix that instead.

FAQ

Sources

We review and cite. We do not reproduce a paper or a manual — follow the links for the originals.

1. [1]Perma-Gard 40 mil PVC Shower Pan Liner — specification and Tile Shower Renovation Instructions — Dallas SpecialtyManufacturer's manual · drain: bond the liner to the top of the drain body (bonding fluid on PVC, silicone on metal or plastic) and clamp it; fold corners with a pig-ear fold, do not cut; nail or staple 1/2 in from the upper edge; at the curb, lay the sheet over the dam, fasten along its front outside the pan and bond two pre-formed corners; turn up at least 6 in; water-test at least 24 hours; read 2026-10-11
2. [2]How to Install a Shower Pan Liner — Oatey · 2022Manufacturer's manual · manufacturer’s project guide, published 2022-10-17: fold corners and glue the folds; staples only in the top 1/2 in of the liner and on the outside of the curb; dam corners bonded where curb meets wall framing; flood test at curb height for at least two hours — pass when the level has not dropped, the area around is dry and no water comes through the ceiling below; read 2026-10-11
3. [3]Tile Shower Drains — Instruction Guide (wood subfloor and concrete slab) — Oatey · 2023Manufacturer's manual · sloped base under the liner at 1/4 in per ft, up to but not over the drain base; weep holes clear of liner material and silicone; flood test with the drain plugged, water just below the top of the curb, minimum 4 hours; pea gravel over the weep holes; minimum 1-1/2 in reinforced mortar bed over the liner, then thinset and tile; Oatey-branded PDF on Oatey’s asset host; Oatey markings are visible on the liner in our Indian Shores and South Pasadena photographs; read 2026-10-11
4. [4]Mold and Moisture Home Inspection Checklist (C 1083) — Ashlee Tziganuk, Jermaine Durham · University of Georgia Cooperative Extension · 2023 (full review)University extension · check for plumbing leaks around tubs and showers; inspect caulking, grout and tiles; look for discoloration, sagging, bowing or wet spots on ceilings and walls; a musty, earthy odor signals potential mold growth; read 2026-10-11
5. [5]A Brief Guide to Mold, Moisture and Your Home — US Environmental Protection Agency · updated 2026Government or standards body · the key to mold control is moisture control; fix plumbing leaks as soon as possible; dry water-damaged areas within 24–48 hours to prevent mold; suspect hidden mold when a building smells moldy with no visible source — back of drywall, under carpet and pad, inside walls around leaking pipes; read 2026-10-11
6. [6]Fix a Leak Week — US Environmental Protection Agency, WaterSense · updated 2026Government or standards body · check the water meter before and after a two-hour period when no water is being used; if it changes at all, there is probably a leak; read 2026-10-11
7. [7]Florida Building Code, Plumbing, 8th Edition (2023) — §421.5.2 Shower lining — International Code Council / Florida Building Commission · 2023Law / code · cited by reference only: the liner rules, including the limit on fasteners near the threshold, are set out on our page What Is Under Your Shower Floor; the ICC page returned 403 to us on 2026-10-11, so the text was not re-read for this page