Find where a radiator valve is leaking, isolate it safely, then tighten, repack or reseal the joint to stop the drip.
RV-01Find exactly where the leak is coming fromWipe the valve and the pipe below it completely dry with a cloth, then put a strip of kitchen roll or toilet paper under the valve. Run the heating for 20-30 minutes and check the paper. A leak at the spindle (where it enters the valve body) usually means the gland nut has worked loose. A leak at the union nut joining the valve to the radiator, or at the compression fitting joining the valve to the pipe, needs a different fix.
RV-02Get set up before you touch anythingTurn the heating off and let the radiator cool, so you're not working with hot water. Lay old towels or a washing-up bowl under the valve to catch drips. Know where your stopcock is (usually under the kitchen sink) and check it turns freely, so you can shut the water off fast if something drips more than expected.
RV-03Isolate the radiator at both valvesTurn the TRV (or manual valve) fully to off. On the other end, turn the lockshield valve clockwise with a spanner or the small cap removed, counting how many turns so you can put it back the same way later. With both valves shut, the radiator is isolated from the rest of the heating system, so you're only dealing with the water already inside it.
RV-04If the leak is at the spindle: tighten the gland nutThe gland nut sits just below the valve handle, around the spindle. Using an adjustable spanner, tighten it clockwise in small eighth-turns, testing for movement each time. Don't overtighten — if it won't stop leaking after a quarter turn or so, the packing inside has worn out and needs replacing rather than just tightening.
RV-05If tightening doesn't work: replace the gland packingWith the valve isolated, undo the gland nut fully and slide it up the spindle. Pull out the old packing (string or an O-ring) and fit new packing or a replacement O-ring of the same size. Screw the gland nut back down and tighten evenly, then check for drips as you turn the valve on and off a few times.
RV-06If the leak is at the compression joint: remake itUndo the compression nut connecting the valve tail to the pipe with two spanners — one holding the valve steady, one turning the nut. Check the olive (the small brass ring inside) for scoring or damage and fit a new one if in doubt. Push the joint back together square, tighten the nut firmly by hand plus a quarter turn with a spanner, and don't overtighten — that causes leaks too.
RV-07If the valve itself is worn out: replace itIf the valve body is cracked, corroded, or keeps leaking after a rebuild, drain the radiator fully using a radiator key on the bleed valve and a bowl underneath, then undo the union nut and unscrew the old valve. Fit the new valve with fresh PTFE tape on the threads, hand-tighten then a further quarter turn with a spanner, and don't force it.
1 each · Replacement radiator valve (TRV or manual)
RV-08Reopen the valves and bleed the radiatorOpen the lockshield valve back to the same number of turns you counted earlier, then open the TRV or manual valve. Bleed the radiator with a radiator key, holding a cloth underneath, until water runs out with no air spitting. On a pressurised (combi boiler) system, check the pressure gauge afterwards and top up via the filling loop if it's dropped below 1 bar.
RV-09Turn the heating back on and check for leaksPut the heating on and let the radiator heat up fully. Check the valve, gland nut and any joints you touched with dry kitchen roll after 30 minutes, and again a few hours later, since small leaks can take time to show. Wipe up any spilled water and dispose of old olives, packing or the old valve with household waste.
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