A vertical pipe filled with air isn't going to stay filled with air for long. The air winds up dissolving into the water under pressure. That's why water storage tanks on pumps need either a mechanism to inject air as needed or a plastic bladder to separate the air and water.
He just said that without an expansion tank, the pressure goes up to 100 PSI and the TPR valve starts leaking.
However if that was heater
See above.
When I moved into my house there was an expansion tank. When I had the hot water heater replaced recently the guy removed the expansion tank. When I questioned this he said the new water heater was designed to not need one. He was apparently right since the pressure does remain constant throughout the cycle.
BTW I'm late to the thread so please excuse if already covered.
Took me a while to figure that out. I installed one since my pressure relief valve kept popping. Thats too many pounds. Don't like the projected life of only 6 years.
Greg
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