Do this first
- Electrics before water. If the wet ceiling has downlights or a fitting in it, switch that circuit off at the consumer unit before anything else.
- Run the standing test, because it answers almost everything. Dry the ceiling below and tape paper to it. Fill the bath to its normal level and leave it standing for an hour without anyone getting in. Check below. Then pull the plug and watch the ceiling for the next ten minutes.
- Read the result. Nothing during the hour, but water below when you pull the plug, means the waste or the overflow. Dripping while it simply sits full means the seal around the bath or the tap tails.
- Do a third pass with someone in the bath if the first two come back clean. A bath that flexes under load opens the seal along the wall, and it will only leak with weight in it.
- Take the weight out of a bulging ceiling only under the conditions on water coming through a ceiling. Plasterboard only, circuit off, bucket underneath, one pierce at the lowest point, nobody underneath.
- Photograph each stage with the time visible. This test sequence is exactly the evidence an insurer or a managing agent will ask for.
Waste, seal, or something behind the panel
| Test result | Cause | Access needed |
|---|---|---|
| Dry while standing full, wets as it drains | Waste, waste seal or the trap below it | Bath panel off |
| Wets while standing full, no draining | Silicone seal at the wall, the overflow seal, or the tap tails and their back-nuts | Panel off, sometimes tiling at the joint |
| Wets only with someone in it | Bath flexing: inadequate support to the cradle or feet, opening the wall seal | Panel off, bath re-supported |
| Wet regardless, including overnight with nobody in the bathroom | Pressurised pipework feeding the taps or the shower mixer over the bath | Detection before opening anything |
| Wets only when the shower over the bath is used | Grout, silicone or tanking on the wall, not the bath at all | Tiling, at the mapped point |
The flexing case is the one that gets missed, because every test done with an empty bathroom comes back clean. A steel or acrylic bath that is not properly supported drops a few millimetres under the weight of water and a person, and that movement parts the silicone along the wall, lets water run behind the tiles, then closes again as the bath empties. Resealing it without re-supporting the bath means doing it all again in six months.
The constant case is the one that needs detection. Pipework feeding bath taps or a mixer runs at pressure all the time, and a ceiling that is wet at three in the morning is not being wetted by a bath. If the shower rather than the bath is the more likely suspect, a shower leaking through the ceiling has the equivalent tests.
What the repair involves
With the panel off, the waste, the overflow, the trap and the tap tails are all visible and testable under running water, which is where most of these are resolved. A failed waste or overflow is replaced and the joint faces cleaned rather than layered with more sealant. A flexing bath is re-supported to the cradle or the feet, packed and bedded so it no longer moves, and only then resealed. Where the leak is in pressurised pipework the run is isolated and pressure tested first, so the opening is made at one place.
Then the reinstatement on both floors. Tiling and sealing in the bathroom, and the ceiling below cut back to sound board, dried, reboarded, skimmed and painted across the whole ceiling rather than patched, because a patched repair always reads. That is bathroom and shower leak repair here, and where the ceiling belongs to a downstairs neighbour, our insurance claims hub covers how the report is used.
When it is not us
- The silicone has clearly perished and the bath is solidly supported. Cutting it out properly, drying the joint for a day and resealing is within reach of a careful homeowner, and it is the correct fix.
- Water is splashing over the screen or out of the curtain. Not a leak. A screen seal or a curtain that needs to be inside the bath.
- The overflow is dripping externally on an older suite. That is a cistern or tank fault elsewhere, not the bath.
- Wet downlights below. An electrician inspects and replaces those once the leak is fixed and everything is dry.
- It is the flat above yours. Access and liability come first: see a leak from the flat above.
- You rent. Report it in writing. Sanitation and water supply installations are the landlord's to keep in repair.