Radiator leaking from the valve
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →⚠️ Always isolate and drain the radiator before working on its valves. Have towels ready — radiator water is very dirty (black iron oxide sludge) and will stain surfaces.
A leaking radiator valve is one of those frustrating problems that catches many homeowners off guard—you'll notice water pooling beneath a radiator or a persistent drip that gradually stains your carpet or floorboards. It happens because the valve's internal seal wears out over time, or the connection where pipe meets valve has loosened slightly through natural expansion and contraction of your heating system. The good news is that some leaks can be fixed in minutes with just a spanner, whilst others require a bit more patience and basic maintenance skills. This guide walks you through identifying where exactly the leak is coming from, what you can safely attempt yourself, and crucially, when it's time to call in a qualified plumber rather than risk water damage to your home. Most valve leaks are straightforward to resolve if you catch them early and follow the safety precautions outlined here.
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Most likely cause & what to check
Identify the exact source — is it leaking from the valve gland (the nut where the spindle enters), or from the compression fitting where the valve connects to the pipe?
For a weeping gland nut: try tightening the gland nut (the smaller nut at the top of the valve body) by a quarter turn using an adjustable spanner — this often stops a slow weep.
If tightening the gland nut does not stop it, you need to isolate the radiator. Close both the TRV (set to 0) and the lockshield valve, counting how many turns to close the lockshield so you can reset it afterward.
Place a bowl under the valve and open the bleed valve to drain. Replace the valve olive and PTFE tape on the thread — a replacement TRV valve head costs £10–£30.
If the leak is from the pipe-to-valve compression fitting, tighten it by a quarter turn. If it still weeps, the olive is damaged and the fitting needs cutting out — call a plumber.
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Frequently asked questions
Is it safe to use my radiator if it's leaking from the valve?
A slow weep or drip is not an immediate safety risk, but you should address it promptly to avoid water damage to walls, floors, and skirting boards. If the leak is rapid or spraying, isolate the radiator at once and do not use it until it's repaired.
Why is radiator water so dirty and black?
That black sludge is iron oxide (rust) that accumulates inside your heating pipes and radiators over years of operation. It's harmless but will stain fabric and carpets permanently, so always place towels and a bowl underneath before opening any valve.
Can I just tighten the valve nut myself without draining the radiator?
Yes—a quarter-turn tightening of the gland nut (the small nut at the top of the valve) can often stop a slow weep without any draining. However, have towels ready in case a few drops escape, and don't force it or you may damage the valve further.
How much does it cost to replace a leaking radiator valve?
A replacement TRV valve head typically costs £10–£30 from a plumber's merchant, and labour for a plumber to fit it usually ranges from £80–£150 depending on your location. If the whole valve body needs replacing or the pipe fitting is damaged, costs will be higher.
What's the difference between a TRV and a lockshield valve?
The TRV (thermostatic radiator valve) controls room temperature and has a numbered dial; the lockshield is a manual on/off valve on the opposite end that remains hidden and locked in position for balancing. Both can leak, but they require slightly different handling when isolated.
Do I need to bleed my radiator after fixing a valve leak?
Only if air has entered the system during repair—you'll notice cold spots or gurgling noise. If you've simply tightened a nut or replaced a valve head, you can usually skip bleeding unless your system shows signs of air lock.