My bedroom radiator (UK here), upstairs, heated fine until yesterday morning, when I found it cold (heating was off all night, as usual). I've removed the thermostatic valve head/knob that controls the water flowing in, and almost immediately I could feel the pipe feeding the radiator in, get warm. All the other radiators work fine.

I cannot press the pin with the pressure of my fingers, but I can do that by re-applying the valve. However as soon as I put it back, the radiator went cold again.

I've tried bleeding the radiator and most of the other ones, and they were all ok. The system is a combi boiler.

Do you think the issue is with the valve and I could simply replace it, or should I try something else/seek someone qualified?

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  • 1
    if you are talking about "removing the valve" do you mean the knob attached to the valve or the bit where the water goes through? Nov 28, 2022 at 12:43
  • @ratchetfreak my bad - I mean the knob only, by unscrewing the ring at the base. The valve pin is now exposed
    – Luca
    Nov 28, 2022 at 13:28

1 Answer 1


Sounds like the thermostatic "head" has failed.

So get a replacement, or you could take one from a room where it is working fine and test with that.

The water valve bit usually fails open or shut so it sounds like that bit is fine.

There are black caps that can be used to hold the water valve open - used to set up the flow valves for each radiator for balancing.

  • It looks like you have a Drayton RT212 valve head. I've found them very reliable and replacements are still available. The ring fitting is interchangeable so you could switch to a different model if you want something more modern looking and easier to turn like a TRV4.
    – James
    Nov 28, 2022 at 13:57

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