John Rumm wrote in
o.uk:

On 04/07/2020 12:14, R D S wrote:
I learned something this week....

If i'm connecting a screw on tap tail to, for example, an isolator
valve i'll use a both end compression one and do away with the nut
and olive on one end.

But you're supposed to get a specific one with a flatter end.
This was news to me (not enormously surprising) and news to the guys
at the local hardware store (perhaps moreso).

Anyway they didn't have any so i'm using normal ones as usual, is
this an issue?

Not in my experience, I have done similar for many years and never had
a problem.

(the argument against doing it is that the end of the service valve
will not have a suitable flat area for the washer to seal against. IME
this is not the case, and the end area of a service valve is much the
same as that of a "made for the job" tap connector)



People will no doubt use loads of PTFE tape in the assumption that the
threads are the seal.