Radiator Leaking from the Bottom
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Post a job — we'll find you an engineer →Turn off the central heating and allow the system to cool before attempting any work on radiator valves or connections.
A radiator leaking from the bottom is almost always a valve connection leak rather than a hole in the radiator body. The most common sources are the valve tail connection, a gland nut on the TRV or lockshield valve, or a corroded plug in the radiator base.
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Most likely cause & what to check
Dry the area around the leak and watch carefully to identify the exact source. Common leak points: the threaded connection where the valve screws into the radiator (valve tail), the nut where the copper pipe connects to the valve body (compression nut), or the gland nut at the top of the valve stem.
For a gland nut leak (dripping from around the valve spindle), try tightening the gland nut half a turn clockwise with an adjustable spanner. Do this with the heating on — if the leak stops, job done.
For a compression nut leak (where the pipe meets the valve), turn the heating off, isolate the radiator using the isolation valve on the supply pipe, then tighten the compression nut gently. Overtightening will split the olive — if one further turn does not stop it, replace the olive.
For a valve tail leak (where the valve screws into the radiator), turn off and drain the radiator, remove the valve, apply fresh PTFE tape to the tail threads (8–10 wraps, in the direction of the thread), and refit.
If the leak is from a blanking plug (the threaded bung in an unused radiator port), drain the radiator, remove the plug, and refit with fresh PTFE tape or a fibre washer.
If the radiator body itself is weeping (a pinhole or weld seam), the radiator needs replacement — radiator leak sealant is a temporary fix only and can cause problems elsewhere in the system.
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