Leaking Shower Tray

What's happening?

A shower tray leak is rarely the tray cracking. It is almost always one of the three junctions around it: the seal between the tray and the tiled wall, the waste connection under the tray, or the tray itself rocking because it was not fully supported when it was bedded. Water finds the gap, runs under the tray and along the joists, and appears as a stain on a ceiling, a lifting floorboard on the landing, or a musty smell with no visible puddle. Because the escape is hidden, the damage is usually well advanced before anyone notices. The clue that separates a tray leak from a screen leak is timing: a screen leak wets the floor while you shower, a tray leak shows up somewhere below and keeps going after you have finished.

What usually causes it?

• The tray bedded on dabs or an uneven floor rather than fully supported, so it flexes and breaks the seal each time you stand in it
• The silicone joint between the tray lip and the tiled wall perished, split or applied over a wet or dusty surface
• A loose or badly seated waste connection, or a compression joint on the trap that has worked slack
• Tiles finishing above the tray lip with no waterproof layer behind them, so water tracks down the back of the tiles and past the tray
• A cracked tray, usually stress cracks radiating from the waste on a tray that was never properly supported
• A tray fitted level with no fall to the waste, leaving standing water sitting against the wall joint
• A shower fitted onto floorboards or chipboard with no tanking behind or beneath it

When should you call a bathroom fitter?

Call a bathroom fitter if the tray moves at all when you stand on it, if there is a stain on the ceiling below, or if the silicone has already been redone once and failed again. Repeat sealant failure means the tray is moving or the water is getting behind the tiles, and neither is fixed with a new bead. A cracked tray, or a tray fitted with no waterproofing behind the tiled wall, means lifting the shower out and rebuilding the base — a fitter's job, not a repair.

What will the bathroom fitter actually do?

• Isolate the shower and test each junction in turn — tray to wall, waste, trap and screen — to prove where the water leaves
• Lift access below or cut a small inspection opening to see how far the water has travelled and what it has soaked
• Remove the tray where it is unsupported or cracked, and re-bed it fully on a solid, level base with the correct fall to the waste
• Apply a waterproofing membrane or tanking to the tray upstand and the tiled walls above it before retiling
• Remake the waste and trap connections and pressure-check them dry before the tray goes back
• Reseal with a sanitary-grade silicone on clean, dry surfaces and water-test the finished shower before leaving

Finding the leak without lifting anything

1. Dry the tray, the joints and the floor completely.
2. Pour water into the tray with a jug, straight down the waste, and check below for twenty minutes.
3. Dry again, then run water only against the wall joint with the shower head, screen door open.
4. Dry again, then shower normally with the door closed.
5. Whichever step wets the ceiling tells you whether it is the waste, the tray joint or the screen.