Thanks, Bob. The pressure is after the PRV (I tested it on the faucet outside the wall), so I believe it's "delivered" pressure (I don't quite know what the definition is). After we run the water, it drops down to about 60s. And as soon we turn it off, it comes back slowly back to 140 or so. So it sounds like a bad PRV as you said. We did have an extension tank installed in Nov last year after we saw leaking. So I assume the extension tank should be good.
Not sure what our model is, I only wrote down the PSI specs and went to lowes to find out they do have one with similar looking. Is that not enough and I should get the same model?
We have shutoff valve on both sides of the PRV, so I think there will be no problem for us to shut them off.
So here goes my question (again): is the PRV from lowes (they only carry one of the same size that we have) good enough, or should I try to find one that we have now? Other than two big wrench, anything else I should be expecting to have before doing it? Also, there is a big (about 1/4 inch) metal wire that bypasses side by side with the current PRV, what's that for? Will there be any problem removing it and puting it back on after we change PRV? (I think it's for grounding, but I am not sure)
BTW, we are in Atlanta, GA.
Thanks again. I will try to take some pictures and post here when/if I do it.