On Wed, 08 Nov 2017 10:40:06 +0000 (GMT)
"Dave Plowman (News)" wrote:

In article ,
Dave m wrote:
replying to Spamlet, Dave wrote: I'm having the same problem as the
original poster. Got some Aluminium Designer Vertical Radiators, no
matter what I do, I cannot stop the tails from leaking. I have tried
regular PTFE Tape, Gas PTFE Tape, Joint Compound and Fernox Sealer.
I have even tried types of tails, including extendable ones that
have a short thread but a rubber seal on the end, thinking this
will surely nail it but to no avail. A frustrating and costly
mistake buying these rads.

Are you certain they've not split open on a thread? Aluminium is
nothing like as strong as steel.

Or perhaps galled from over-tightening the tapered thread, so the
sealing face is rough and the thread is stretched and no longer tapered.