Roger Mills (aka Set Square) wrote:

Some modern taps have very poor flow rates when fed with tank pressure
rather than mains pressure.

Noted, thanks.

If you're feeding a tap with cold water at mains pressure and hot water at
tank pressure, it's important that the hot and cold have independent paths
all the way to the discharge nozzle - rather than mixing further back in the
tap. Maybe this was what the man behind the counter was saying?

That sounds about right from memory.

If the
mixing takes place further back, the mains pressure cold can push the low
pressure hot *backwards* up the feed pipe. I think you're supposed to fit
double check valves to prevent that sort of thing anyway - but I'm not sure
how many people do!

The counter man mentioned this as well.
Many thanks for your input to my question. It looks like I will have to
as at the plumbing supplier.

Regards

Dave