Tricky Dicky wrote:

You need some of these;

https://www.screwfix.com/p/flomasta-...er-union-22mm-
x-1/27982

Or

https://www.screwfix.com/p/compressi...er-22mm-x-1/50
777

If you do not want to solder. In either case the male thread on the
cylinder needs wrapping with PTFE tape

Richard

The first link you mention is a union fitting - the seal is made by a
metal to metal seal of the male conical brass part in the fitting and
the female conical part of the fitting on the tank. PTFE on the
threads won't help make a watertight seal as water can simply pass
between the nut and the pipe if the conical union does not seal.

If the surfaces of the union fitting are good enough this is a very
reliable seal. If the fitting is distorted or too pitted or worn to
seal then the second option you link to can be used, the seal being made
to the threads, though preferably with either hemp and sealant or the
Loctite thread sealand which comes as a "string" of ptfe and stuff. 1"
is very much on the big side for sealing with PTFE tape. More
especially since AFAICS neither thread is a taper one. The !" female
to compression adapter should be available in a 1" taper BSP female
thread which I would prefer if I was doing it. But the proper union is
better if it works as there is a risk of damaging the fittings on the
tank if over tightened.

--

Roger Hayter