How to Fix a Leaking Radiator Valve

Finding the Source of the Leak

Before you start, identify exactly where the water is coming from. Common leak points on a radiator include: the valve at the base of the radiator (manual or TRV), the union nut joining the radiator to the pipework, or the radiator body itself. Leaks from the radiator body usually mean a replacement is needed.

Tightening a Dripping Valve

If water is dripping from the valve gland (the nut just above the valve body), try tightening the gland nut a quarter turn clockwise with an adjustable spanner. Don't overtighten — if it still drips after a quarter turn, stop and reassess. Overtightening can damage the valve permanently.

Replacing Valve Packing

If the gland nut is already tight but still leaking, the packing inside the valve has worn out. Turn off the water supply to the radiator (close both valves), wrap PTFE tape around the spindle beneath the gland nut, and re-tighten. This often stops the leak without a full valve replacement.

Replacing a Radiator Valve

If the valve body is cracked or the leak is at the union fitting, the valve needs replacing. This involves:

1. Isolating the radiator by closing both valves
2. Draining the radiator into a container
3. Removing the old valve and replacing with a matching type (manual, TRV, or lockshield)
4. Reconnecting with fresh PTFE tape and re-pressurising

This job is straightforward for a plumber but can be messy if you don't have experience draining radiators. Call us if you'd rather have it done cleanly and correctly.