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Discuss What size is this rad/valve connection? picture included in the Central Heating Forum area at

  1. StuartP

    StuartP New Member

    Hi all.

    I'm removing the rad in the picture for decorating and want to blank off the connection from the thermostat/valve to the rad (will do both ends obviously). The thermostat/valve has 1/2 bsp stamped on it but pretty sure the connection to the rad is not 1/2 bsp, I have a couple of 1/2 bsp blanking caps but these are too small. Does anyone know what size the connection to the rad is?

    Many thanks in advance.

  2. heliotrope

    heliotrope Plumber GSR

    I would say that is 1/2 inch.

    How do you know that what you have is too small, have you tried to
    fit it?
  3. Last Plumber

    Last Plumber Plumber GSR

    It is 1/2"
  4. StuartP

    StuartP New Member

    I haven't tried to fit it yet but the 1/2 bsp fitting I have looks way too small when offered up against what you see in the picture. Spanner size is also smaller on the 1/2 bsp fitting I have.
  5. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    this is what you need


    the 1/2 refers to the connection to the pipe
    • Useful Useful x 1
  6. StuartP

    StuartP New Member

    Many thanks Shaun. I figured that that was the case but had no way of sizing the connection. I'll get a couple before taking the rad off. Thanks again, Stuart
  7. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    note that wont work for the pipe end if your removing the trv
  8. StuartP

    StuartP New Member

    I'm not removing the trv at this point, just need the rad off for plastering and paint. Cheers again
  9. Allgoode

    Allgoode GSR

    That trv & lockshield will be quite a few years old so may have a bit of a seep especially the TRV head side.

    Also that TRV variant only closes to the frost-guard (4 degree's approx) setting unlike the newer variants which goes to full shut-off, something to bear in mind at this time of year.

    Some towels around bottom of pipes are also a good idea if carpet is fitted to stop potential staining.

    Good luck,

  10. StuartP

    StuartP New Member

    Ok, so I've bought a couple of the blanking nuts that Shaun kindly gave the link for but these are too small as well. I've not actually tried to fit them but when you offer them up they look way too small. Could the rad connection be 22mm? As you can see in the pic the pipe work is 15mm but I'm clutching at straws here a bit. Plasterer coming on Monday and I need this rad off and the connections blanked. Any thoughts anyone?

    Many thanks in advance
  11. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    It should fit as it's a standard 15mm nut and olive
  12. StuartP

    StuartP New Member

    I hear what you're saying Shaun but they're too small. Just to clarify, I'm talking about the connection/union between the trv and rad. Given that the trv is deffo 1/2 bsp as it's stamped on it, shouldn't the union also be imperial and not metric. The union is obviously bigger than 1/2 bsp, so could it be 3/4 bsp?
  13. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Surely the cap that Shaun is in about screws straight onto the valve not the tail for the radiator?
  14. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!


    If it's the tail end you want op it's a 1/2 cap you need
    • Agree Agree x 1
  15. StuartP

    StuartP New Member

    But I've already tried 1/2 and it's too small. Could the union be 3/4 bsp?
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