Leaking radiator
Radiator leaks usually come from a valve at one end. Dry it all, wrap tissue round each joint, and the wet one tells you where.
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How to stop a leaking radiator
- Turn the heating off.
- Close the valve at each end of the radiator, turning clockwise. One end may need a spanner or the cap from the other valve.
- Put a bowl and towels under the drip.
Where a radiator leaks from
Dry the radiator, both valves and the pipes. Wrap dry tissue round each valve nut, hold some under the bleed valve and run a sheet along the bottom edge. Open the valves again, heating on, and watch.
| Where it is wet | What it usually means | Who fixes it |
|---|---|---|
| 1A valve nut or the valve spindle | A loose nut, a worn olive or tired packing round the spindle. Very common, and often a small fix. | You or a plumber |
| 2The bleed valve at the top | The bleed screw is not closing properly, or the valve itself is worn. | Plumber |
| 3Along the bottom of the radiator | Rust has made pinholes in the radiator. It needs replacing. | Plumber |
| 4Where the pipe comes out of the floor or wall | The leak may be on the pipe below the floor, with water running up to where you can see it. | Leak detection, then a plumber |
Isolation steps as advised by councils and radiator suppliers, for example Southwark Council: turn off leaking radiators.
Who fixes a leaking radiator
A confident DIYer can gently tighten a weeping valve nut once the radiator is isolated. If the drip carries on, the bleed valve leaks, or the radiator needs draining, call a plumber or heating engineer.
Do not overtighten. Old valves and olives crack, and a weep becomes a spray.
After any radiator fix
Check the boiler pressure. Draining or bleeding a radiator lets water out of the system, so the gauge may need topping up to the range in your boiler's manual.
Hidden central heating leaks
Heating pipes run under floors and inside walls between radiators. A leak there shows up as a boiler that keeps losing pressure, a warm or damp patch on the floor, a stain on the ceiling below, or water appearing at a radiator that is dry itself.
If every radiator, the boiler and the small copper pipe that runs from the boiler to outside are all dry and the pressure still falls, the leak may well be on a hidden pipe. The leak finder walks you through it.
Pipe wet where it leaves the floor?
If the water starts where the pipe comes out of the floor or wall, or the boiler keeps losing pressure with every radiator and the copper pipe outside dry, the leak may be on a hidden heating pipe. ADI traces it and marks the leak on site before any repair is discussed.
- 25 leak investigation engineers, around 5,000 jobs a year across England, Scotland and Wales
- A fixed price quoted before you book, and a written report you can give your insurer
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ADI figures as of September 2026, from ADI's About page. Trustpilot rating read 28 September 2026.
Leaking radiator questions
What happens if a radiator is leaking?
The heating system slowly loses water, so the boiler pressure drops and you keep having to top it up. The water that escapes stains carpets, rots floorboards and can come through the ceiling below. Topping up also brings in fresh water and air, which adds to corrosion inside the system.
How urgent is a leaking radiator?
A slow weep from a valve nut that you can catch in a bowl can wait a day or two once you have closed both valves. Water that is spraying, pouring, or dripping through to the room below needs dealing with now: close the valves, turn the heating off, and call a plumber.
How expensive is it to fix a radiator leak?
Tightening or repacking a valve is usually a small job. A leaking pipe joint means draining the radiator. A radiator with pinholes needs replacing. A leak on a pipe under the floor needs finding first, which is where leak detection comes in.
This site does not publish prices. Ask for the work to be quoted once the source is known.
How long can I leave a leaking radiator?
Not long. Even a slow drip keeps soaking whatever is under it, and every top up of the boiler adds air and fresh water to the system. Isolate the radiator by closing both valves and get it fixed as soon as you can.