This is a followup "Lesson Learned" to my leaking 1972 Overlander conundrum.
Never trust a single water pressure reading! I really tore into the plumbing and finally uncovered my "problem." The water kept leaking and I finally plugged the overflow tube form the overpressure relief valve. This was fine until the water heater pressure relief started blowing-off!
I checked the incoming water pressure again and found over 120 psi! Opps. My pressure relief valve was doing its job and I defeated it! I also realized a P.O. had removed the stock water pressure regulator.
$5.00 later I installed a plastic but effective pressure regulator on the incoming hose - SOLVED.