dennis@home wrote:

On 17/05/2019 13:55, Roger Mills wrote:
On 16/05/2019 17:24, Adam Funk wrote:
Just to be clear, I'm talking about combining these two parts:

Compression Wallplate Elbow 15mm x 1/2"
https://www.toolstation.com/compression-wallplate-elbow/p74070

Hose Union Bib Tap with Double Check Valve 1/2" DZR
https://www.toolstation.com/hose-uni...le-check-valve
/p54792


I was under the impression that if you install the elbow so that
supply pipe is coming straight down to it, the tap should screw all
the way into it& end up pointing down. (I'm pretty sure that's what
I did with the old ones, which were removed as part of a kitchen
renovation, so I've installed new ones in a different place outside.)

In practice, however, I installed two of these the same way but they
ended up pointing in slightly different directions, neither straight
down. I ended up packing a couple of fibre washers in each elbow
until I got the right direction. What am I missing?

Thanks.

If it worked in the past, it was pure coincidence. You can have the
supply pipe coming in at any angle, so to have something which only
worked at one angle would be silly. The threads are tapered, and thus
seal on the threads rather than bottoming against a flange - so fibre
washers are no good. You just need sufficient packing round the thread
to make it go tight at the desired orientation. As others have said,
hemp plus Boss White or whatever is far better than PTFE tape for this.

All the bib taps I have used have parallel threads.

Me too. But 1/2' is small enough to be able to seal parallel threads
pretty well, and, in the absence of a suitable washer, a wodge of PTFE
tape squeezed out at the end plus enough on the threads to make it stff
has always worked for me. If it leaks at first try it will be a slow
leak, and you can re do it until it gets tight at the right point and
doesn't leak. Most things can go wrong in my hands, but I've usually
found it quite easy, reassured by the fact tha a slight leak is not
usually a disaster for most bib tap applications. Sealing the threads
with PTFE or one of the other suggestions at least ensures that anly
leak will be very small, and makes accidentally unscrewing it less
likely.



--

Roger Hayter