Thermostatic Radiator Valve Question

[nashville]

I need to replace some TRVs on my central heating system.

After removing one of the old ones, I can see that the joint between the TRV and the radiator tail is the union type (ie. not compression). After looking on the Screwfix site (yes, I know, but they are good value!), its really hard to tell which of their TRVs are union joint and which are compression.

If I buy the wrong type, I suppose I will have to swap the tails as well. If I do this will the TRVs with compression joints actually fit without having to alter the pipework as well? Are all rad. valves the same dimensions? Are certain makes of TRV compression, and other makes union?

 

[John506]

When you buy a TRV a new tail will come with it for you to fit into the rad.

 

[bengasman]

After looking on the Screwfix site (yes, I know, but they are good value!),

if you are talking about their lowest price trv, you are wrong.
they are not good value, just cheap