Pipes bang once, when I flush toilets, turn on washing machine, or turn on some faucets. My pressure from city is 45lbs. First I checked my expansion tank (located just before hot water tank) pressure valve squirted water, replaced that tank. Problem still there , opened wall up and braced some pipes- no change. Changed one of the toilets inards, thought maby faulty valve, no change. I've adjusted the pressure valve several times and it seems to help for a while then pipe knock again. The house is 7plus years old with radient heat however this heat system seems to have no conection to problem. The hot water tank is 50gal and ballanced the expansion tank to the system as instructions stated. Where does one go from here ? I think the pressure adjusting valve may be faulty however dont want to keep replacing parts for not. Any ideas ? Thanks for reading.