The point that no-one has made.
If you have a hot tank running at mains pressure, what happens
when you heat the water? Correct, it expands, but if it cannot
expand then (Boyle's Law?) the pressure within must increase
until you get to the ultimate - tank failure with all of the
The main idea of the cold header tank is that it feeds both the
hot and cold bath taps (and any gravity fed shower) so both
supplies are at the same pressure when delivered. If you have one
tap from a hot tank and the other from mains then it will be
difficult to balance flow and/or temperature, and there is also
the possibility of back-feed via a mixer tap or similar which is
harrogate three at ntlworld dot com
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