On 20/02/2021 19:28, Fredxx wrote:
I would normally use thick PTFE tape, but I'm not happy with the feel.

I used 150-200mm of tape and I can keep turning the tail onto the
radiator and if anything gets looser as I keep turning. Yes I have
wrapped in the right direction!

Is there any advantage to using thin tape, or is there a preferred or
recommended sealant which hardens to form a seal. Where some modest
torque needs to be applied to remove the tail (in the unlikely event it
need to be removed).

It needs to seal on the threads before bottoming out. Screw the tail in
without any tape and see how far it goes in. Then take it out and wrap
it with tape. It needs to go tight before it goes in as far as it does
without tape. I always use tape designed for use for gas pipes. It's
thicker and stronger than the standard stuff.
--
Cheers,
Roger