The stain is not directly under the bathroom — how?

Water runs along joists and cables before it drips, so it emerges at the lowest point or at a break in the ceiling such as a light fitting. The stain marks the exit, not the entry.

Should I pierce a bulging ceiling to let the water out?

It relieves the weight and can prevent a collapse, but do it from the side with something long, with a container underneath, and never standing directly below. Turn the lighting circuit off first.

It only leaks when the shower is used — what does that mean?

That points at the shower itself rather than a pipe: a failed tray seal, an enclosure sealant that has let go, or a waste connection that only passes water under flow. A continuous leak with nothing running points at a pressurised pipe.

The water is coming from the flat above — whose problem is it?

The leak is theirs to fix; the damage is usually a matter for the buildings insurance and the lease. Notify the occupier and the managing agent early, because a plumber cannot fix a leak they cannot reach.

Emergency

Updated 30 August 2026

Water Coming Through The Ceiling

A stain, a drip or a bulge has appeared in a ceiling below a bathroom, kitchen or flat above.

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What's happening?

Water shows in a ceiling a long way from where it entered. It runs along the top of the plasterboard, follows joists and cables, and drips at the lowest point or wherever a light fitting breaks the surface — so the wet patch is evidence, not the location. Above a bathroom, the usual sources are a shower tray or bath seal, a waste connection, a leaking supply pipe or an overflowing appliance. In a flat, it may not be your pipework at all. A ceiling that is bulging rather than staining is holding water above it and is the urgent version of this problem.

What usually causes it?

Failed seal around a bath, shower tray or wet room floor letting water past the edge every time it is used
Leaking waste connection at a bath, shower or basin trap directly above
Split or pinholed supply pipe in the floor void, leaking continuously whether or not the room is used
Toilet pan connector or a leaking cistern seal releasing water each flush
Overflowing loft tank or a failed float valve running into the ceiling below
Washing machine or dishwasher hose in a flat above discharging into the floor
Grouting or sealant failure in a shower enclosure, soaking the substrate behind the tiles

Is it dangerous?

Yes, on two counts. Water in a ceiling void sits directly on cables, ceiling roses and downlight housings, and a saturated ceiling is an electrical risk before it is anything else — switch off the lighting circuit, or the main switch, before going near it. Second, wet plasterboard loses its strength quickly and a bulging ceiling can drop as one heavy sheet. Keep people out from underneath, and never poke at a bulge while standing below it.

Can I fix it myself?

Stop the water reaching the ceiling: turn off the stop tap if the leak continues with nothing running, and stop using the bathroom above. Switch off the affected lighting circuit and move furniture clear. Put a container underneath and, if you have to relieve a bulging ceiling, do it from the side with something long, never from directly below. Finding the source is the part to leave alone — cutting exploratory holes in the wrong place usually costs more than the leak did.

When should you call a plumber?

Call a plumber straight away — same day. Call before that, and get everyone out from under it, if the ceiling is bulging, if water is running rather than dripping, or if it is coming through a light fitting. If the water is coming from a flat above, tell the occupier and the building's managing agent at the same time, because access to their property is usually what settles it.

What will the plumber actually do?

Isolate the supply and the affected electrical circuit before opening anything
Trace the source with moisture readings, and by testing the bathroom above under controlled use rather than guessing
Lift boards or open a small inspection area at the identified point and repair the failed pipe, waste or seal
Re-seal or re-bed a bath, shower tray or wet room upstand where the water is bypassing the edge
Pressure-test the repair and re-test the fitting above under use before closing up
Advise on drying out and what has to be replaced before the ceiling is made good

Frequently asked questions

We’re happy to answer all your questions.

Sources & References

Burst PipeEmergency Leaking Shower TrayCaution Damp Patch On The Ceiling Below The BathroomCaution Leak Under The Kitchen SinkCaution

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