"Colin Wilson" o.uk wrote
in message g...
I've had very good customer service from Plumbworld, so here's a prod
in their direction :-)
Alternatively, you can get "dial up pressure reducing valves" like
this:
He needs the equalising valve.

Daft question perhaps, but why would the pressure reducing valve not
work ? - ISTM that it's only the massively unequal pressure of the
cold that's overpowering / restricting the flow of the hot out of the
shower.

FWIW ours does the same if I open the valve too much on the shower*
(although you still get very good flow rates)

* a thermostatic Hansgrohe

An equalising valve drops the highest pressure to the lowest and makes the
hot and cold equal. If a tap is turned on, or a toilet flushed, there is
slight glitch and then the pressures equal out and scalding or cold shocks.