In article ,
a wrote:
we bought some new taps for the bathroom and the sink ones went
in fine (apart from struggling to get some ptfe tape on the
joints up underneath the sink!). However when I came to put the
bath taps in the nut on the water pipes only goes a couple of
turns up the taps thread before stopping (so the pipe is loose).
I dont want to force it and damage the threads, but what is wrong
here? The old taps are 8 years old, and look like the same 3/4"
thread when held next to the new one (pitch looks the same and
thread profile appears the same), but on both hot and cold the
nut only goes up a couple of turns. Any ideas before I trot off
to the store tomorrow with tap in hand to find something that
will fit?

When the nut apparently bottoms does it feel as if
is stops hard (as if against a stop) or does it feel
as if the nut slowly grinds to a stop.

The hard stop, but still loose, could be that you do
not have the (fibre?) sealing washer in there.

The soft stop could suggest a crossed thread, or a
different thread on the tap.

--
Tony Williams.