How to Fix a Leaking Radiator Valve
A leaking radiator valve is almost always one of three failures: gland packing, olive seal, or the valve body itself. Diagnose the leak point first — then pick the right fix. All three are DIY-friendly with a spanner and PTFE tape.
Step-by-step method
1. Identify the leak point
Wipe the valve dry, then use kitchen roll to pinpoint where water reappears. Top spindle = gland. Nut where pipe enters valve = olive/compression. Body seepage = replace the whole valve.
2. Fix a leaking gland (most common)
Turn off both radiator valves. Unscrew the top cap and gland nut. Wrap 4–5 turns of PTFE tape clockwise around the spindle threads. Reassemble and open valves. This works on 80% of drip cases.
3. Reseal a leaking compression nut
Drain the radiator side of the valve. Undo the compression nut, slide it back, cut and replace the olive (or add 2 wraps of PTFE around the existing olive as a temporary fix). Retighten firmly.
4. Replace the entire valve
If the body leaks, isolate the water, drain the rad, undo both unions and swap for a new TRV or lockshield. Use jointing compound plus PTFE on threads. Ideal upgrade opportunity to a modern TRV.
Frequently asked questions
Can I fix a leaking radiator valve without draining the system?+
For gland leaks yes — both valves closed is enough. For olive or full-valve swaps you must drain that radiator using the lockshield and bleed valve.
What's the best sealant for radiator valves?+
PTFE tape (gas-rated pink for the paranoid) plus Loctite 55 or Fernox LSX on threaded connections. Never use silicone on the wet side.