Quote Originally Posted by rspears View Post
A water heater tank is a pressure tank, designed for around 150psig working pressure, and something like 300psig design pressure...
Oops!
Mea culpa!
We're talking at cross purposes here...here in New Zealand water heater tanks are thin-walled copper tanks with a pressure reducing valve between them and the mains system, designed for quite low pressures.
What you call a water heater tank is what we refer to as a water pressure cylinder, a different beast entirely.
I wasn't meaning to denigrate Mike P; the different names for different style things had me fooled.