Harold Kestenholz
Absolutely right about that, Sylvan. I am still puzzled about this post. I was not aware of non-diaphragm expansion tanks being used on such installations. I have never used or sold one for this purpose.
Certainly ASME high-pressure vessels are used commercially, but I am still curious about this use on a residential system. Piped so the expansion tank is above the heater, air bubbles separating from the water as it is heated would collect any air and hydrogen produced in the process, so purging would not be necessary until hydrogen collects. The tank would have more than enough air; so the tank in this post must be too small. Then I would not encourage a smoker to purge the tank. If this is an old boiler expansion tank in use on a water heater, I expect to hear the report from a long distance at any time.
