Silly question but hours of research failed to answer it. The PRV that is installed is working fine and matches the pressure flow rate charts that Zurn-Wilkins has. Meaning that the fall in pressure between locked and open is within the charts they provide online. With no faucets on the pressure is say 60 PSI. With a heavy flow it will fall to just under 50 PSI. With a light flow 55 PSI. Question 1: when setting the PRV to a recommended pressure, say 50 PSI, is that the bottom, top or no flow? 50 PSI locked up with no flow would be around 40 PSI with a heavy flow. Question 2: When setting the expansion tank PSI, is it done to the locked up pressure, light flow or heavy flow? Question 3: Is the expansion tank air pressure set with zero pressure in the lines or is it set with the system pressurized. These questions do not appear in any articles or literature I can find. The articles and literature always says set the PRV to the desired pressure but that is a range according to load.