MEANLIN MEASURE 0~160Psi Stainless Steel 1/4" NPT 2.5" FACE DIAL with Reset Pointer Liquid Filled Pressure Gauge WOG Water Oil Air, Lower Mount, with 1/8" x 1/4" NPT and 1/8" x 3/8" NPT Hex Bushing

Should dry fit and ask before soldering. It is forward thinking idea to put a bypass and also installing a pressure gage. Like a previous comment said, PRV should be on the main straight line not on the loop. Also I will use 3 way valves on the both ends of bypass loop so that you have straight line for water flow during normal operation and avoid stagnant water trapped in those loop. BTW, I had hard time finding a water pressure gage that is oil filled ( avoid false fluttering pressure from shut off) with a max indicator needle. Here is one I got and very and happy with it. pressure gage