Bath or Shower Seal Leaking? How to Spot It and What to Do Next

A worn seal around your bath or shower tray looks like a small cosmetic job, but it’s one of the most common reasons for water damage in a bathroom and the ceiling below it. If the sealant is cracked, black or peeling, or you see damp after a shower, stop using that shower and check it before the water does more damage. If you’re in Clare, Sudbury, Haverhill, Long Melford or a village nearby, here’s how to spot a leaking bath or shower seal, what you can safely check, and when to hand it to a plumber.

Why a small gap in the seal matters

The bead of sealant (usually silicone) where your bath or shower tray meets the tiles stops shower water running down behind the bath and under the floor. When it splits or comes away, a little water gets through every time someone showers. Which? Trusted Traders’ plumbers say that the sealing on baths wears away over time, that a small leak can build up under the floor over days, and that most bathroom leaks they see start at the seal around a bath with a shower over it.

Signs your bath or shower seal is leaking

• The sealant is cracked, split, shrunk away from the tiles, or has black mould growing behind it.
• Grout or tiles near the bath or tray feel soft, loose or have gaps.
• The floor next to the bath or shower feels spongy, or the flooring is lifting or stained.
• A brown stain, flaking paint or a damp patch appears on the ceiling below, especially after showers.
• A musty smell in the bathroom that doesn’t clear with ventilation.
• The bath moves or flexes slightly when you step in, which can pull the seal open each time.

Step by step: what to do if you think the seal is leaking

1. Stop using the shower over the bath (or the shower tray) for now. A bath with no shower running is usually less of a problem, but if you see any water below, stop using it too.
2. Look closely at the seal with a torch. Check the whole length, especially the corners and the end under the shower head, where water hits hardest. Press gently: sealant that lifts or feels hollow has failed.
3. Check the room below. Look for damp, staining or bulging on the ceiling. If the ceiling is sagging or water is near a light fitting, keep everyone out of that room and follow our guide to water coming through the ceiling.
4. Keep water away from electrics. Don’t touch light fittings, shaver points, an electric shower or its pull cord if they’re wet or near the leak. If a trip switch (RCD or circuit breaker) has gone off, you may reset it once, only with dry hands and a dry floor. If it trips again, leave it off and call a registered (Part P) electrician.
5. Work out if it’s the seal or a pipe. If damp appears only when the shower is used, the seal or tray is the likely cause. If it appears when the shower hasn’t been used, or keeps dripping all the time, it’s more likely a supply pipe or a joint under the bath, and the water needs turning off.
6. If it’s dripping all the time, turn the water off. Close the bathroom isolation valve if you have one (a small valve with a screw slot; a gentle quarter turn closes it, so don’t force it). Otherwise turn off the inside stopcock, usually under the kitchen sink. Our guide shows how to find and turn off your stopcock.
7. Take photos and notes. Photograph the seal, the floor and any ceiling marks, and note when the damp appears. Which? Trusted Traders’ plumbers advise telling your plumber where you think the leak is coming from, because it saves time finding it.

Can I reseal the bath myself?

Replacing a worn bead of sealant on a sound, dry bath is a common household job, and many people do it themselves. Follow the sealant manufacturer’s instructions, remove all the old sealant, and make sure the surface is completely clean and dry first. Silicone won’t stick properly to a wet or mouldy surface, and sealing over a gap just traps water behind it.

Don’t simply put new sealant over the top if water has already got under the bath or floor, if the bath moves when you stand in it, or if tiles are loose. Those need the cause sorting first, or the new seal will fail and hidden damage will carry on. Don’t lift floorboards, take off bath panels near hidden pipes, or cut into walls to look for leaks.

When to stop and call us

• There’s a stain, bulge or drip on the ceiling below.
• The floor by the bath or shower is soft, or the bath or tray moves when you step in.
• Damp appears even when the shower hasn’t been used, or water is still escaping with the isolation valve or stopcock off.
• Water has reached light fittings, an electric shower or other electrics, or a trip switch won’t stay on.
• You’ve resealed and the leak has come back.
• You can’t find or turn your stopcock. See our help on a seized or leaking stopcock.

Our leak detection service can trace water hidden under floors and behind baths, our plumbing team can reseal and repair baths and shower trays, and for a bigger refit we offer bathroom installation. As NAPIT registered electricians, we can also check wet electrics once the water is off. If a lot of water is coming through, call our emergency plumbing team.

The outside or boundary stop tap is usually owned by your water company (Anglian Water or Essex & Suffolk Water) and may need a special key, so don’t dig it up or force it. If you think there’s a leak on their side, check whether neighbours are affected and contact the water company.

Stop it happening again

• Every few months, look along the bath and shower seals. Replace sealant as soon as it cracks, blackens or lifts.
• Wipe the seal dry after showers and keep the bathroom ventilated to slow mould growth.
• Keep the shower screen or curtain closed while showering so water doesn’t sit on the seal.
• Which? Trusted Traders’ plumbers suggest running a hand around the pipe joints you can reach in the bathroom every six months or so, and knowing where your stopcock is.

Smell gas or suspect carbon monoxide? Leave the property, open doors and windows if it’s safe, don’t use light switches or naked flames, turn the gas off at the meter only if it’s safe to do so, and call the National Gas Emergency Service on 0800 111 999. Get medical advice if anyone has CO symptoms such as headaches, dizziness or nausea. Only a Gas Safe registered engineer may work on gas appliances; you can check an engineer on the Gas Safe Register.

Sources and further reading

• Which? Trusted Traders: tips on five common plumbing problems (leak through the ceiling)
• Which? Trusted Traders: how to stop a water leak
• Anglian Water: your stop tap
• Electrical Safety First: bathroom electrical safety

This is general safety guidance. If you’re unsure, stop and call a qualified engineer.