Leaking Bath: How to Find Where It Is Coming From

Updated July 2026 · Emergency Plumber Chelsea

First, contain the damage. If water is showing on the ceiling below, put a bucket under it and move anything valuable out of the way. If the stain is near a light fitting or the ceiling is bulging, switch off that lighting circuit at the consumer unit and do not use the light. Our guide on water coming through a light fitting explains what to do next. Then stop using the bath and shower over it until you know what is leaking. Take photos of the ceiling and the bath area before anything is disturbed, as insurers usually ask for them. If you are not sure the bath is the culprit, our guide to a leak in the ceiling below a bathroom covers testing the shower, toilet and basin too.

Next, take the bath panel off if you can. Most side panels clip or screw on and come away with a gentle pull from the top edge or by removing a few screws along the plinth. With a torch, look underneath at the waste, the overflow pipe that runs from the hole near the top of the bath down to the waste, and the tap connections at the end. Feel for damp with a dry hand or a piece of kitchen roll. Look for water marks, white or green crusting on joints, and wet or darkened floorboards. Very often the leak is obvious once the panel is off.

If nothing is obvious, test each part separately. Start with the supply. With the bath empty and the taps off, dry everything under the tap end and leave kitchen roll under the connections for an hour. If it is wet, the leak is on the pressurised supply: the tap connectors, the isolation valves or the pipework. Those leak all the time, not just when the bath is in use, and you may notice the water meter creeping with everything turned off. Our how to find a water leak guide covers the meter test.

Then test the waste. Put the plug in and run a few centimetres of water into the bath, then check underneath around the plughole fitting. If it is dry, pull the plug and watch the waste and trap as the water drains. A waste that leaks only while draining usually has a loose or perished seal where the plug fitting meets the bath, or a trap nut that has worked loose. Hand-tightening the trap nuts sometimes solves it. A leaking plughole seal needs the waste fitting taking out and resealing, which is a small plumbing job.

Then the overflow. Fill the bath until water is running into the overflow hole, briefly, and check the overflow pipe and its connection behind the bath. The overflow is one of the most common hidden leaks because it is only used when someone overfills the bath or climbs in with it full, so it can go unnoticed for months. The rubber washer behind the overflow grille perishes with age and, in an older bath, the flexible overflow hose can split.

Finally, the silicone seal. With the waste and overflow ruled out, if the ceiling only gets wet after showers rather than baths, the most likely culprit is water getting behind the seal along the wall or through failed grout in the tiles above. Splash some water along the seal with a jug and look underneath and on the ceiling below. Mouldy, cracked or lifting silicone, or a gap you can slide a fingernail into, is a giveaway. Baths move slightly when they are filled and someone gets in, which is why a seal that looked fine when it was done can crack. Our guide on a leaking shower tray covers the same seal and grout problems in more detail.

Resealing a bath properly is not just running new silicone over the old. The old silicone has to be cut and scraped out completely, the joint cleaned, dried and degreased, and, importantly, the bath filled with water before the new sealant goes on, so the joint is set with the bath at its heaviest. Otherwise the first full bath pulls it open again. Leave it to cure for the time on the tube, usually a day, before using it. If the bath itself flexes badly, which is common with thin acrylic baths on weak frames, the feet or cradle may need adjusting too.

Some leaks need a plumber rather than a tube of silicone. Leaks from supply connections and valves, a waste fitting that needs resealing, a split overflow hose, a cracked bath, and anything where water has been getting into the floor for a while all fall into that group. In Chelsea's period houses and mansion blocks, baths often sit over lath and plaster ceilings and timber floors, and a slow leak can soak into joists before it shows below. If the ceiling below has been wet for more than a day or two, it is worth having it checked properly once the leak is fixed. A persistent damp patch with no obvious source is where our leak detection service earns its keep, as it traces leaks without taking up more of the floor than necessary.

If the leak is affecting a neighbour's flat, tell them and the managing agent straight away, and read our guides on a ceiling leak from the flat above and who is responsible for a water leak. Damage from a sudden leak is often covered by buildings insurance as escape of water, while the repair to the bath itself usually is not, so keep your photos and the plumber's report.

If your bath is leaking and you cannot find the source, or water is already coming through the ceiling, call Emergency Plumber Chelsea on 020 3002 6667. We find and fix bath leaks in houses and flats across Chelsea, Knightsbridge, South Kensington, Sloane Square and Fulham, and our bathroom plumbing service covers reseals, new wastes and overflows, tap connections and bath replacement. There is no call-out fee on jobs over 3 hours.

Quick tips

• Remove the bath panel and look underneath with a torch before anything else.
• Test supply, waste, overflow and seal separately so you know which part leaks.
• Wet only after showers usually means the silicone seal or the grout above it.
• When resealing, fill the bath with water first so the joint sets at full weight.
• If water is near a light fitting, turn off that lighting circuit and keep clear.

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