Pressure equalising valve

See the makers specs for minimum pressure and flow. They sometimes don't operate too well when the pressure difference is too large.

Yes.

Yes.

Why?

purpose is to put both supplies on the lowest common denominator. If one supply is poor, it makes the other equally so. You first need to get two good supplies.

The correct solution is to put a single impellor pump on the hot side, to boost the hot water system to mains like pressure and flow. Then you can worry about pressure equalising, although this will only really be advantageous on a shower mixer, which a good model will have built in (along with thermostatic operation).

An alternative to the pump is to fit a "venturi" type shower, which uses energy from the cold mains to boost the hot water through the mixer. This won't help other outlets, like the bath taps, that might also have poor flow.

It is required for hosed shower mixers unless you put one of those intensely annoying clips on the shower hose that prevents you using the shower to clean the bath/cubicle with.

Christian.

Does anyone know where you can get single impeller pumps? I've not found any on-line and wouldn't mind getting one for our HW system in general.

I believe someone recently recommended the Grundfos UPA 15-90 "Home Booster".

The other manufacturer normally recommended is the Stuart Turner. They do quite a number of single impellor pumps, from their entry level Showermate

Christian.

The Grundfoss is quite cheap. When having booster on hot and cold on the mains, it is best to check the pressure of both. Ideally they should be near each other. If they are then a pressure equalizing valve will trim off.

Cheers for those. I'll go and see what I can find, but can anyone recommend somewhere that sells 'em?

Plumb Center for the Grudndfos.

How about using a dual impellor with both sides in parallel?

cheers, Pete.

You can't pump main water.

I think he meant to use both impellers on the hot side. However, this is unnecessary. Single impeller pumps are widely available and cost less than the equivalent twin impellers.

Christian.

Having Google'd by brand name I turned up half a dozen places selling 'em. Never realised they were that common as, although I kept hearing about them, I'd never found any before just looking for "single impeller", etc. And the sheds never stock such things.

Ta very much. I've got one of those local, too.