Leak in the Ceiling Under a Bathroom
A leak in the ceiling under a bathroom usually comes from one of four places — the shower or bath seal, a waste or trap joint, the toilet connection, or a supply pipe — and the timing tells you which: drips only after use point to seals and wastes, a constant drip points to a pipe under pressure.
A leak in the ceiling under a bathroom usually comes from one of four places — the shower or bath seal, a waste or trap joint, the toilet connection, or a supply pipe — and the timing tells you which: drips only after use point to seals and wastes, a constant drip points to a pipe under pressure. A stain, bulge or drip in the ceiling under a bathroom or en-suite.
What is actually going on
A stain, bulge or drip in the ceiling under a bathroom or en-suite.
The realistic causes, in order
Failed sealant or grout around a shower tray or bath, letting water past the surface finish A waste connection leaking only under discharge, so it appears intermittently A supply pipe leak, which shows as continuous rather than use-related dripping
What we test on site
Whether the leak is continuous or only when a particular fitting is used, which narrows the cause quickly Waste connections and trap seals with a controlled discharge test Supply pipework under pressure test where a continuous leak is indicated
Protecting the ceiling while you wait
Put a bucket under the drip and, if the plaster is bulging, make a small hole at the lowest point so the water drains in one place rather than bringing a larger area down. Keep electrics off near the wet patch. Stop using the bathroom above until the source is found, and close the stopcock if water keeps coming with nothing running.
Questions we get asked
What causes a leak coming through the ceiling below a bathroom in a bathroom?
Failed sealant or grout around a shower tray or bath, letting water past the surface finish
What normally puts a leak coming through the ceiling below a bathroom right?
Identifying use-related versus continuous leaks first means we open the minimum amount of ceiling.
Should I switch anything off because of a leak coming through the ceiling below a bathroom?
A bulging ceiling holding water can collapse suddenly. Keep people out from underneath and isolate the electrics if a light fitting is involved.
What should I do first when water comes through the ceiling below the bathroom?
Stop using the bathroom, turn off electrics to any light fitting the water is near, and if water keeps coming with nothing running, close the stopcock. Then note when it drips — after a shower, after a bath, or all the time — as that points to the source.
Is a leak only after showering usually the tray or the seal?
Very often. Failed silicone, grout or tray waste seals only leak when water is running over them, whereas a supply pipe leak drips whether or not anyone has used the bathroom.