Leaking Bath? How to Find Where the Water Is Coming From
Water under the bath or a stain on the ceiling below? Four simple tests to tell a sealant leak from a waste, overflow, tap or supply pipe leak, what you can fix yourself and when to call a plumber.
Most bath leaks come from one of five places: failed sealant where the bath meets the wall, the waste fitting under the plughole, the overflow seal, the taps or tap connectors, or a supply pipe under the bath. You can narrow it down in an afternoon. If water appears when nobody has used the bath, it is a pressurised pipe or tap connector, so turn the water off at the stopcock and call a plumber. If it only leaks when you shower over the bath, it is almost always the sealant or grout. If it leaks when you fill the bath, it is the waste or overflow.
Key Takeaways
- A leak when nobody has used the bath points to a supply pipe or tap connector: turn the water off and call a plumber.
- A leak only when showering over the bath is almost always sealant or grout.
- A leak when the bath is filled points to the waste or overflow seals under the bath.
- A bath that flexes when you stand in it will keep breaking its seal until it is supported properly.
- Photograph any ceiling damage before repairs if you may need to claim on insurance.
Most bath leaks come from one of five places: failed sealant where the bath meets the wall, the waste fitting under the plughole, the overflow seal, the taps or their connectors, or a supply pipe under the bath. The quickest way to narrow it down is to note when the water appears. If it shows up when nobody has used the bath, a pressurised pipe or tap connector is leaking, so turn the water off at the stopcock and call a plumber. If it only happens when you shower over the bath, it is almost always sealant or grout. If it happens when you fill the bath, look at the waste and overflow.
Is it urgent?
A bath leak can go unnoticed for weeks behind the panel, then show up as a brown stain or a bulge in the ceiling below. How fast you need to act depends on what you can see.
- Water dripping through a ceiling light or fitting: switch that circuit off at the consumer unit and do not touch the fitting. Water and electrics need an electrician's check before the light is used again.
- A sagging or bulging ceiling: keep people out of the room below, put a bucket underneath, and call a plumber straight away. Do not poke it unless a professional tells you to.
- Water appearing when the bath is not in use: turn the water off at the stopcock. A supply pipe or connector under pressure will keep leaking day and night.
- A small stain that only grows after baths or showers: stop using the bath or shower over it, and work through the tests below.
Where bath leaks come from
| Source | When it leaks | Typical sign |
|---|---|---|
| Sealant and grout | When you shower over the bath or splash the wall edge | Black or peeling sealant, gaps you can push a fingernail into |
| Waste fitting | When the bath drains | Water around the plughole fitting and trap under the bath |
| Overflow | When the bath is filled to the overflow | Drips from the overflow pipe behind the bath end |
| Taps and connectors | When the taps run, or all the time | Wet flexible connectors or a damp tap body |
| Supply pipes | All the time, whether the bath is used or not | Damp that keeps spreading and a water meter that keeps turning |
| Bath movement or a crack | When someone stands or sits in the bath | Sealant that splits again soon after resealing |
Plastic and acrylic baths flex more than steel or cast iron. If the bath dips when you step in, the sealant will keep tearing until the feet and cradle are adjusted and the bath is supported properly.
Four tests to find the leak
Take the bath panel off if you can. Most push-fit panels pull away from the top edge. Dry everything underneath and lay dry kitchen roll under the waste, the overflow and each tap connector, so you can see exactly where new water lands.
Leave the bath unused
Leave the bath and taps alone for a couple of hours. If the tissue gets wet, a supply pipe or tap connector is leaking under pressure. You can confirm it by checking whether your water meter moves with every tap in the house off.
Run the taps with the plug out
Run hot and cold for a minute each into the empty bath. Water at the tap body or connectors points to the taps. Water at the waste and trap as it drains points to the waste fitting.
Fill the bath
Put the plug in and fill to just below the overflow. Wait ten minutes. Then top up until water runs into the overflow. A leak at the first stage is the waste seal. A leak only at the second is the overflow seal or its pipe.
Splash the edges
With the bath empty, use a shower head or jug to run water down the tiles and along the sealant line, one wall at a time. Water appearing behind the panel means the sealant, grout or screen seal is letting it through.
If none of the tests reproduces the leak but the ceiling keeps getting wet, the water may be coming from somewhere else, such as a shower tray, a toilet or a pipe running under the floor. Our leak detection service finds hidden leaks without lifting more floor than necessary.
What you can fix yourself
Sealant. Resealing is the most common fix and a reasonable DIY job. Cut and scrape out every trace of the old sealant, clean off mould and soap, and let the joint dry completely. Fill the bath with water before you seal it, so it settles into the position it sits in when in use, and leave it full until the sealant has cured. If the grout above the bath is cracked, regrout that section too.
Waste nut. If the leak is at the trap or the large nut under the plughole and you can reach it, a gentle hand tightening may stop it. Do not overtighten plastic fittings, as they crack. If it still drips, the washer under the waste has probably perished and the waste needs resealing.
Tap connectors. A weeping connector sometimes only needs a quarter turn. Isolate the tap first if there is a valve. If the flexible connector is corroded or bulging, replace it rather than tightening it, as those can fail suddenly.
If the bath is cracked, or the leak is on a soldered or compression joint on the supply pipes, call a plumber. A failed repair here floods the room below.
When to call a plumber
Call a plumber when water appears without the bath being used, when the leak is on the supply pipework or taps, when resealing has not worked, or when you cannot get the panel off to see. A plumber will reseal or replace the waste and overflow, fit new tap connectors, check the bath is properly supported and trace any leak coming from nearby pipework. If the bath needs replacing, see our bath installation service.
Water coming through the ceiling below the bath?
Tell us when the leak appears and where the water shows. Our labour is £95 an hour and the £60 call-out is waived on jobs over two hours. We confirm the price before any work starts.
📞 Call 020 7870 3200More on our leak repair service and leaking shower repairs.
Ceiling damage and insurance
Once the leak is fixed, let the ceiling dry out before redecorating. Plasterboard that has sagged or softened usually needs replacing rather than painting over. Stains that come back through fresh paint are a sign the area was still damp.
Many home insurance policies cover sudden escape of water damage, but many exclude gradual leaks and failed sealant or grout. Photograph the damage and the source before anything is repaired, keep the plumber's invoice showing the cause, and check your own policy wording. Our guide on whether home insurance covers plumbing explains the usual exclusions, and our water damage repair guide covers drying out.
If you live in a flat and the stain is in your neighbour's ceiling, tell them and your managing agent in writing. If your shower rather than the bath is the problem, see our guide to a leaking shower tray.
Frequently Asked Questions
Why is my bath leaking through the ceiling?
The most common causes are failed sealant or grout where the bath meets the wall, a loose or perished waste or overflow seal under the bath, a leaking tap connector, or a supply pipe under the bath. If the stain grows even when nobody uses the bath, it is a pressurised pipe, so turn the water off and call a plumber.
How do I find where my bath is leaking from?
Test one thing at a time with the bath panel off and dry tissue under the fittings. Leave the bath unused and check for water. Run the taps into the empty bath with the plug out. Fill the bath below the overflow and wait. Then shower over the wall edges without filling. Whichever test produces water tells you the source.
Can I fix a leaking bath myself?
Replacing failed sealant is a straightforward job if you remove the old sealant completely, let the area dry fully and fill the bath with water before sealing so it sits at its loaded position. Tightening an accessible waste nut can also help. Leaks from supply pipes, tap connectors or a cracked bath are best left to a plumber.
Why does my bath only leak when I shower?
When water only escapes during a shower over the bath, it is getting past the sealant, grout or shower screen rather than through the plumbing. Water runs down the tiles, finds a gap where the bath meets the wall and drips behind the panel. Resealing, and sometimes regrouting, usually fixes it.
Does home insurance cover a leaking bath?
Many buildings and contents policies cover sudden escape of water damage, such as a ceiling below a bath. Many exclude gradual leaks and failed sealant or grout. Check your own policy, photograph the damage before any repairs, and keep invoices that describe the cause.
Sources and further reading
Source links checked 27 September 2026. Scheme rules and manufacturer instructions can change; use the current official guidance for your account or exact appliance.