dp wrote:
I'm fitting a mira excel shower but I'm confused. The instructions say
a drop tight pressure reducing valve (PRV) to be fit if the supply
exceeds 5bar maintained. I suspect that my pressure is quite high (it
comes out of the cold tap a lot faster than the hot tap) the hot tap is
fed by a worcester 25si which I understand provides hot at 2.5 bar.

The shower instructions also say the shower works best if the two
supply pressures are equal.

Does a PRV allow you to set the output pressure to a certain setting?

Alternatively I've seen some pressure equaling valves he

http://cgi.ebay.co.uk/Pressure-reduc...QQcmdZViewItem

Should I try one of these instead?

Any advice / Experience of Miras appreciated.

Thanks.

A pressure reducing valve is a good thing to have in any installation
where there are high static pressures. It should increase the life of
valves in washing machines, water softeners, combis, etc. The term
"pressure _reducing_ valve" is a bit misleading, as they are really
static pressure _limiting_ valves. They are usually adjustable, but in
any case are normally set to around 3.5 bar. You install it just after
the stop cock on the incoming mains supply.
e.g. http://www.bes.ltd.uk/products/110.asp

The item you linked to is a pressure equalising valve. It contains a
diaphragm that automatically maintains equal pressures in the hot/cold
feeds (within reason - it's not really intended to be used where you
have mains cold and gravity hot, for example).

The hot water is bound to have a lower pressure than the cold, as it
has been through the narrow pipes of the heat exchanger in the combi.
You may find that part closing the cold service valve for your shower
improves things a bit, without the expense of an equlising valve.

-Antony