David Lang wrote:

Quick one really - When fitting a 1/2" into a wall plate, do I need to put
anything on the thread first (like PTFE), or is this not necessary.


Why not use it?

I'd always use PTFE tape personally, costs a few pennies and ensures a leak
free joint.


It's far better to understand the purpose of PTFE in a joint and use it
accordingly than to just use it on every joint.

In this case, it's a parallel thread joint, which will require some kind
of sealant to make it water tight. PTFE (or alternative) is therefore
required.

However, there are many other types of joint where the seal is created
in a different way (metal/metal, metal/rubber etc.), and using PTFE in
those situations is neither desirable nor recommended.


--
Grunff