Find the exact leak
- Spindle — top of the valve where the handle turns.
- Union nut — between the valve and the radiator tail.
- Tail — where the tail screws into the radiator.
- Pipe nut — where the pipe enters the valve.
Pro tip: Wrap dry tissue around each part separately. The first one that gets wet is the leak.
Fixes
- Spindle: tighten the small gland nut a little. If it still weeps, isolate and wrap PTFE or packing around the spindle under the nut.
- Union nut: hold the valve with one spanner, tighten the nut a quarter turn.
- Pipe nut: hold the valve, tighten a quarter turn. If it still leaks, the olive may need replacing — drain down first.
- Tail thread: drain, remove the tail, clean, rewrap with PTFE, refit.
Don't overdo it
Over-tightening squashes olives and cracks unions. A quarter turn at a time, then dry and wait.
Corrosion
Green or white crust around a valve means a slow leak for a long time. The valve may need replacing.
