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Noritz tankless gas water heater
I sold a contractor a Noritz 199,000 BTU input TGWH and he installed it in his showroom as a live fired unit. What happens when the unit is done running and it stops making hot water the relief valve pops off and a little amount of water runs out of the relief valve. They have high incoming water pressure and I told them to install a PRV unit to reduce pressure. He said no he likes high pressure. Then I suggested to install a small thermal expansion tank. Putting the expansion tank on the cold water inlet pipe to the TGWH would that keep the relief valve from popping?