A shower tray that leaks is usually the silicone
I found a wet stripe on the bathroom floor in November, just outside the cubicle door. The heating had been on a week and the room stayed damp after a shower. I thought the waste had split. I dried the trap and put a cloth under it. The cloth was dry the next morning. The wet was a dark line along the wall, coming from under the lip of the tray.
I had already had a go at it in the spring. I wiped the old bead with a cloth and laid a new one on the smear. It looked white and neat. Within a week it had pulled away from the tile. Water was running behind the skin, under the tray, and out onto the vinyl.
A shower tray sits on the floor or on a foam plinth. The waste takes the water that goes down the hole. The only thing that stops shower water going under the tray is the silicone at the wall and the silicone at the cubicle. If that bead has shrunk, split, gone mouldy, or been smeared onto dirt, it is not a seal. The water does not need a cracked trap. It needs a gap at the joint.
I checked the waste because that is the scare. The bottle was dry. The hose nuts were dry. The wet sat along the wall, not under the outlet. That is the bead.
With the water off I ran a finger along the wall-to-tray joint and the tray-to-cubicle joint. The wall bead moved. It had a black crumbly skin and a split at the back corner, the bit you do not see when the door is shut. Under the lip, away from the waste, the underside of the tray was wet. That is not a trap failure. That is shower water finding the gap and sitting under the tray until it finds a way out.
Check the joint before you buy a new tray. Look for a split, a mouldy skin, or a bead that lifts when you press it. Look at the floor after a shower, then look again an hour later with the cubicle dry. A wet stripe that grows from the wall, not from the waste, is the silicone. If you can see under the lip, a wet line on the tray itself, away from the outlet, is the same story.
Getting it back is the old bead off, a dry seat, and a new bead that actually meets the tile and the tray. Cut the old silicone out. Do not smear it into the gap. Get the residue off the tray lip and off the wall. White spirit on a cloth if the skin has left a film, then a clean wipe and time to dry. The joint has to be dry. If the board behind the tile is wet, stop. If the floor under the tray is rotten, stop. If you cannot get the old skin off without lifting the tray, isolate the shower and stop. Do not open a waste you cannot put back. Do not re-pipe. Do not open a live supply you cannot isolate.
Then a clean gap and a bead that fills it, tooled so it meets both faces. Leave it to cure before you run the shower. The new bead has to bite clean plastic and clean tile. Last year's mould is not a seat.
Skip laying new silicone on the old skin. The new bead has nothing to bite. Skip lifting the tray with the supplies still live. Skip opening the waste to have a look when the trap is dry and the wet is at the wall. Skip a new tray because the silicone failed.
I do not need a new tray because the joint wept. I need the old seal off, a dry seat, a bead that actually meets the wall, and a stop if I cannot isolate or the floor has gone.
This is the same failure as A sink that weeps at the rim is usually the seal. New silicone on a dirty smear is not a seal in either room.
If I later add a buy link here, it will be a paid promo.