Thanks for that - slight pity you didn't give us that the first time as
it gave Drivel an excuse to pollute the air with his political
dribblings.

Having also reread the initial posting, I would agree with what you are
saying; it would seem that the OP's dhw system has a fault in it that
is creating the low pressure - either due to the configuration, or to
furring up or the likes. A pump therefore is not going to solve his
problem as the feed - either out of the hw tank or into it from the cw
tank - just in't great enough. Cavitation will result.

I am expecting that my set-up - 28mm feed to hw tank and seperate 22mm
feeds to bathroom and the rest will be ok with the Grundfos pumpin the
'rest' feed. The requirement is to overcome a 2.5m head to the kitchen
where her-in-doors had me fit a continental style spray mixer tap which
is on a shower head type hose and consequently a high pressure drop.

Rob