Radiator valve leaking — how to fix it
Check the steps below first — if you're not confident, get it fixed safely today.
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Most likely cause & what to check
First determine where exactly the leak is coming from — the valve body, the valve tail (where it screws into the radiator), or the compression joint on the pipe.
For a weeping compression joint: try tightening the compression nut by a quarter turn with a spanner. This often stops minor leaks without any draining.
For a leak from the valve gland (around the spindle): you may be able to tighten the gland nut slightly to compress the packing inside. Only tighten until the leak stops — overtightening makes the valve stiff.
For a persistent leak or a cracked valve body, you will need to isolate the radiator — close both valves fully (turn clockwise until firm). Bleed the radiator to release pressure. Put towels and a bucket under the valve, then undo the union nut to remove the leaking valve and replace it.
Wrap PTFE tape on any threaded connections before refitting.
If the system needs draining to do the repair, refill it and check pressure before restarting the boiler.
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🛠 Tools & materials you may need
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Frequently asked questions
Can I isolate one radiator without draining the whole system?
Yes — close both the TRV and the lockshield valve fully before disconnecting. Have a bucket and towels ready as a small amount of water will escape.
What is the white residue around a leaking valve?
Limescale left by evaporating water. This is a sign the leak has been going on for some time. Clean it off with white vinegar once the leak is fixed.