"Nodge" wrote in
:

Just been doing a bit of plumbing in the bathroom. I've fitted a 15mm
isolator valve in the feed to the wc. I suspect the copper pipe is the
old imperial 1/2" dia but I understood that the 15mm fitting would be
ok. I've tightened the nut on the isolator valve as much as I dare but
I've still got a small leak. It seems to be coming from between the
pipe and the nut rather than from the threads of the nut. (I put PTFE
tape around the thread). What's the best way to get a watertight seal?

Compression joints don't require anything at all; I use a bit of grease on
the moving parts, and they shouldn't need a terrible lot of tightening.

Worst case - you may have a deformed pipe, (and you may have just deformed
it) in which case a new bit will have to be inserted, or replace the run if
reasonable.

It may have been a faulty olive; the olive certainly will be faulty by now!
Try again with a new olive. (You can buy them separately, in case you
weren't aware)

mike