[dbld58]

https://www.amazon.com/RVGUARD-Pressure-...5437404462

You need something with an adjustment knob and an internal diaphragm. The one you used will not work for what you are trying to do.

I can understand why you might think the first one you listed would migrate because it is adjustable. But the adjustment ring locks when you have it where you want it.

I set the first one to 20 psi to start.  It would stay there for the first few flushes, but overnight it went to 55 psi which is where the main system's pressure was at the time.

I'll give the one you listed a try though.