Bath Leaking From the Waste or Overflow
- How urgent
- Caution
- Who fixes it
- A plumber
What's happening?
A bath drains through a waste outlet in the base, a trap below it, and an overflow that joins the waste. Each connection is a rubber washer or a plastic nut, and each leaks only while water is running through it. A leak from the waste outlet shows as soon as the bath holds water. A leak from the overflow shows when the water rises to the overflow slot, or when you pull the plug and water rushes past. A leak from the trap or the connection to the waste pipe shows while the bath empties. A bath that moves and cracks sealant is on the bath flexing page; a leak at the taps is a supply fault.
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What usually causes it?
- A perished washer on the waste outlet where it meets the bath
- An overflow hose or banjo connection that has split or loosened
- A trap nut worked loose or a cracked plastic trap
- A cracked or split waste pipe joint after the bath has flexed
- Failed sealant around the bath edge letting water run behind the panel
- A bath that has moved and pulled the waste connections apart
- A condensation drip that looks like a leak on a cold pipe
Is it dangerous?
Medium. A slow leak rots floor timbers and stains the ceiling below before anyone notices. If the water reaches a light fitting or a socket, switch off that circuit at the consumer unit only if you can reach it without standing in water, and use the electrical emergency page.
Can I fix it myself?
Take off the bath panel if there is one and look. Dry every joint, put paper under each, and run an inch of water, then pull the plug while you watch. Paper wet at the outlet means the washer; at the banjo connection, the overflow; at the trap nut, the trap. Tighten a plastic nut by hand, not a tool. A new washer or trap is a straightforward replacement if the bath has access. Do not use silicone as a washer replacement. If the leak is hidden behind a tiled panel or the bath is fitted in a concrete floor, stop using the bath.
When should you call a plumber?
Call a plumber when there is no access panel, when the leak is at the waste outlet and needs the bath lifted, when the ceiling below is stained, when the waste pipe is cracked, or when you cannot find the source.
What will the plumber actually do?
- Open the panel and test the outlet, overflow and trap with the bath full and during emptying
- Replace the outlet washer and seal, the overflow hose or the trap
- Repair or replace a cracked waste pipe and its fixings
- Re-seal the bath edge and check that the bath is supported so it does not flex the waste
- Check the floor and ceiling below for water damage and dry readings
Who fixes this
- Waste and overflow pipework
- Leak repair
What it usually costs
- Leaking Pipe Repair Cost
- £100–£500 for an emergency burst pipe
Questions people ask
Why is my bath leaking underneath?
Why does the bath leak from the overflow?
Why is there a stain on the ceiling under the bathroom?
Can I keep using the bath?
Sources & References
Before you book, read what to check before a plumber starts.
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