Connecting a pressure gauge - male parallel thread.

[thinkingsquirl]

Hello,

I'd like to connect a pressure gauge to a 22mm copper water pipe. I've been thinking that I'd use a reducing tee to 15mm and then an adaptor 15mm to 1/4" female thread to keep the component count down. The problem I see is that the gauge has a 1/4" male parallel thread and the adaptor has a 1/4" female parallel thread. Should I add an 'o' ring onto the base of the male thread (the gauge) for a seal and/or use Loctite? Is it possible to get a good seal on parallel to parallel threads? Is there a better way of fitting a male threaded pressure gauge onto a water pipe?

I also have a pressure switch to fit that has a female 1/4" parallel thread. Should I use a male 1/4" tapered thread adaptor to achieve a good seal, or use a parallel male and an 'o' ring and/or Loctite.

Sorry for such a basic question. Any help would be appreciated. I'm not in the trade but would like to give this a go to see if I'm thinking along the right lines.

The pressure gauge:

 

[Chalked]

Loctite, or ptfe will do the jobb

 

[Ray Stafford]

Don't over-think it. A few turns of PTFE tape will deal with it.

 

[snowhead]

You can buy an adapter from gauge fitting to taper.
But as others, PTFE and wrap it like string under the nut to act as a washer in case it screws all the way in.

Trim all the spare PTFE off after, it always looks cack to see pfte dangling off threads.