I have finally got around to removing an old damaged Stelrad radiator - I have an identical one waiting to go on the wall but despite using a fair amount of force, the connectors don't appear to want to come off. Looking inside them, the olive seems quite damaged anyway.

Is best practice to buy a new pair of these - and what should I ask for if so? I can get whatever measurements I need from them but am unsure what is important.

Here are some pictures of the connections. Obviously these are the bottom of the radiator - I have inverted it to show more clearly.

I can't see where to get a good grip: enter image description here

Detail inside: enter image description here

New radiator: enter image description here

6 Answers 6


what should I ask for if so?

Radiator valve tails

I can't see where to get a good grip

Use a large allen key (hex key) inserted into the bore. Probably 12.7mm (½") "radiator key" / "radiator spanner"

Workarounds include

  • Use a smaller allen key wedged in with a flat screwdriver
  • Attach an old/spare radiator valve, tighten the nut and turn the valve to unscrew the tail.

whatever measurements I need

I surmise they're standard across the UK. My habit is to take the old parts to the store when buying replacements. A specialist plumbers supply store will have someone knowledgable behind the counter. Last time I did something like this (but not this), I walked in, silently plonked the old part on the counter, almost before it hit the counter the bloke behind it casually reached under the counter and then placed an exact replacement part on the counter next to mine and told me the price.

Source: How to Install a Radiator


The piece in your first photo is a Union.

I would replace all of them with new unions.

A union allows you to De-couple the radiator from the plumbing if you ever need to replace or remove it.

You will need a male thread on the radiator side to match the female threads on the radiator tail piece and the other side will need to match the pipe you are connecting to, ( male, female or solder.)

Since it is on the bottom you may need a 90 degree union, it will be dependent on your plumbing set up. I would go to a dedicated plumbing supply house to insure you get the proper units.

You will want to use pipe dope or Teflon tape on the radiator side threads but NOT on the threads that couple the union together.


I vote to replace everything. Look for a thin bodied clamping wrench. I know it would be a pain but you could soak the fitting in vinegar.


0 down vote

You can clean the threads with a soft wire brush without being too aggressive and clean the tapered area very carefully with a very fine steel wool (not sandpaper), so as not to score the taper and cause a leak that can't be stopped. Make sure to clean both pieces, the one on the radiator and the one in the picture. If the tapered area is rough or deteriorated in any way, you could coat the tapered area with a thin coating of RTV silicone and tighten the union nut.Do not use teflon tape on the tapered area, use silicone only. If however, you have to replace the fittings, I would have it done by someone with the proper tools and experience so as not to ruin the radiator or piping.

  • While your answer to my other post is helpful, this one completely fails to answer the question.
    – Rory Alsop
    Commented Feb 4, 2018 at 13:18

Usually new valves comes with connectors, so I suggest you to change the whole assembly, getting the opportunity to install a thermostatic valve that can help you saving on heating costs.


Replace the tail & Nut. I usually get a small hacksaw and cut the nut off. Makes it easier to remove the tail piece. Goodluck!!

  • 4
    This doesn't add anything that wasn't already posted in the accepted answer 5 years ago. Please feel free to edit this to add more detail if you have something else you'd care to share. Also, take the tour to see how we work around here.
    – FreeMan
    Commented Sep 8, 2023 at 11:23

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