On 09 Apr 2012, you wrote in uk.d-i-y:
view.co.uk:

As there is a washer supplied with the FI adaptor then that would
be sufficient for the job.
If you don't trust the washer alone then you could put a few wraps
of tape on the male thread but don'nt over do it.About eight turns
would be enough. You should rough up the thread first with a file
or hacksaw blade.

Whatever you do I would not rough up anything.


Smooth, clean and lightly lubricated is the best principal. If the face
is intended to be the seal then don't put anything on the thread.
Usually only tapered thereads perform a sealing role. Washing machine
and compression fittings do not use the tread for sealing purposes - the
thread serves to pull things together.