Thanks for the responses.
The explanation from GE seems more valid as I think about it.
I have a 4.4-gallon expansion tank installed, with an initial setting of 40psi. I just checked it and it’s at ~86psi now. It makes sense that it would seek a balance with the rest of the system.
It seems to me that in order for the expansion tank to be effective, it must have an initial pressure higher than that of the system as a whole. Is that true? If so, how much higher?
I’m a little nervous about charging that tank up to 100psi to compensate for a system that’s overloaded to begin with. It’s rated for 150psi, and I can almost hear the explosion now!
So I bought a few PRVs and plan to install one of them. They’re both made by Wilkins; one’s a model 70 and the other is a 600. The difference is that the 600 has a separate integral strainer cavity and costs $13 more. The price difference is nominal and I want what makes sense for my system.
If I have a water filter installed before the PRV, I don’t think I need the separate strainer. Does it make more sense to install the PRV before the filter, which case I can definitely see the value in the separate strainer?