3/4 BSP radiator / what trv?

Discussion in 'Plumbers' Talk' started by SuperJohn, Sep 10, 2017.

  1. SuperJohn

    SuperJohn New Member

    I've removed a couple of radiators, and they are 3/4inch BSP fittings; I know this is correct as that's the blanking caps I used.

    I want to replace the valves when I refit them, and the thought it sensible to use trv's. I thought they came with suitable tails (think that's the correct term) but the ones I've picked up from screwfix don't. I'm now struggling to find ones that specify that they can be used with 3/4 BSP radiator's that aren't really really expensive. Have I got any other options, some kind of adapers that won't mess up the valve spacing or something?

    Be gentle with me, I'm a total plumbing newbie!
     
  2. Wayners

    Wayners Active Member

    I'm not a plumber although I dabble. I think you need one of these as I bought one years ago from merchants. I never new screwfix stocked them. Click Here

    BUSH ¾ X ½ adapter
     
  3. dobbie

    dobbie Well-Known Member

    Are you sure the tails are not 1/2" when you say you have used 3/4" caps.
    A lot of valves join together using 3/4" male and female fittings.
     
    Last edited: Sep 10, 2017
  4. nigel willson

    nigel willson Well-Known Member

    As above . That rads not 3/4 it's the tail screwed into it! Fit try , you fit the tail supplied with it
     
  5. SuperJohn

    SuperJohn New Member

    Dobbie - I'm probably not using the correct terminology, but the big captive nut thingies on the radiators are expecting a 3/4 inch thread to screw onto, which the current (very painty and a but leaky :) ) valves have. The TRV's appear to have what I am referring to as 'tails', but they appear to be a 1/2 inch thread (I think), but either waym they are way to small.

    Wayners - that bush thingie looks ideal. In fact when I did the rads in another room, the bog standard valves I used their to replace the old ones came with something like that I think that allowed them to fit, but I could be mis-remembering.
     
  6. SuperJohn

    SuperJohn New Member

    Sorry nigel - posts crossed - I see what people mean now; I'll pop outside to look at the rads.
     
  7. dobbie

    dobbie Well-Known Member

  8. terrymac

    terrymac Active Member

    bound to be 1/2 inch bsp.think op is referring to the valve union
     
  9. SuperJohn

    SuperJohn New Member

    OK, so I've removed the tail screwed into the rad. It is the brass thing on the left in the photo (see link below). What I am assuming is the new tail is in the middle, and the threaded bit fits the rad OK. But how on earth does the smooth bit of the tail form a seal with the valve? I was expecting it to be sort of flared, like the brass one, so the nut, that's presently on the valve, would have to be put on the tail before it was screwed into the rad, and would then butt up against a seal when tightened, if you see what I mean. Have I got the wrong TRV or am I missing something?

    Thanks for all the help and advice so far, it's a steep learning curve but the help on here has been invaluable.

    https://photos.app.goo.gl/7pbhx7aVuj8FTqjy1
     
  10. Wayners

    Wayners Active Member

    Tail fits the valve. Olive squeezes tight and forms a seal like any compression joint. I can see olive in pic
     
  11. dobbie

    dobbie Well-Known Member

    Wrap PTFE round the threaded part of the tail and then fit it to the radiator,make sure you use enough.
    When you have hung the radiator on the wall, then fit the valve to the pipe and the tail,use a little bit of water hawk paste or hawk white on the olives to help seal.
    If you have to buy the paste get water hawk as that can be used on potable water fittings.
     
  12. terrymac

    terrymac Active Member

    your new valve just has a different style of joint . the silver tail ( which is 1/2 inch thread not 3/4 ) goes into the rad and you need to wrap PTFE tape around the thread to make a seal ,before fitting it.the trv valve is jointed onto the smooth end ,by compressing the olive ,by tightening the nut.
     
  13. SuperJohn

    SuperJohn New Member

    Oh my goodness, what a knobber, can't believe how dumb I am sometimes. So it works exactly like the copper pipe joint at the other end of the valve? Can't believe I didn't notice that. Doh!

    Told you I was a newbie, lol. Thanks again for the (patient) advice!
     
    terrymac likes this.
  14. SuperJohn

    SuperJohn New Member

    Sorted; Both rads put back on with the trv's / new lockshields, and they don't appear to be leaking anywhere. Cheers folks.
     

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