In article ,
Rick wrote:

I have a thermal store .. so no cold storage tank at all ... cold and
hot are both at mains pressure ... massive flow rates, at great pressure.

I have great pressure from the mains (8bar), but a piddly low flow
rate. There is a blockage/kink/crush in the buried pipe coming into the
house which I don't currently have the resources to look for (ie. dig
down through the tarmac/concrete/rubble to find) That's the only reason
I keep the big tank in the loft...

Gordon