On 11/09/16 15:14, Peter Clarke wrote:
But I would add that my concern is people downstairs at breakfast
time flushing loos and using mains cold at the kitchen sink; this
will reduce pressure and flow to the showers if everything depends on
incoming mains.


Shouldn't do.

Not if you spilt 24mm cold from right after the stopcock to geed
everything but the hot water tank.
Roof mounted tanks are always less pressure than mains is. So as long as
you have adequately sized pipework you will always do better with mains
pressure than a header tank.



--
Karl Marx said religion is the opium of the people.
But Marxism is the crack cocaine.