Parallel or tapered threads on new rads?

[nicam49]

Hi All, I'm learning loads of new stuff by reading threads on this excellent forum (old dog too!)... but last night I was reading on here about rads and extension tails, and followed a link to a Screwfix product that was a tapered tail,.. but reading the Q&As there, the 1st Q asked if it was NOW a tapered thread... suggesting that previously the product had a parallel thread (probably by mistake?) Which has got me wondering which type of thread to expect on a new rad. Here's the link:

https://www.NoLinkingToThis/p/tesla...d-trv-extension-piece-60mm/2456r#BVQAWidgetID

I'm particularly interested as I'm replacing a rad in the near future....
Thanks for any advice!

 

[Last Plumber]

The female thread in the rad is normally parallel. The male thread entering it is supposed to be tapered so that it tightens into the female. With the use of jointing compound or PTFE etc. That tightening creates the joint. If done correctly, it won't leak.

Some rad valve manufacturers use what appear to be parallel threads on their rad tails. This means that the male thread will screw all the way into the female until it reaches the end. The joint relies on an abundance of PTFE (or whatever else) to prevent it from leaking. It may work for a time but I personally wouldn't leave it like that. The joint is useless.

Buy good quality rad valves with properly made tails is my advice.

 

[nicam49]

Thanks! That's really useful knowledge that I wouldn't have got for anywhere else. Many thanks, Esteemed Plumber! 👍