Hi,
I'm planning on fitting a mixer shower and the instructions suggest that when used with a combi system, it may be a good idea to also install a pressure equalising valve (PEV). Does anyone have any experience of this? Is it worth the extra expense to install a PEV?
Thanks,
Murdo
The valve does help in the mixing of the hot and cold water at the mixer unit itself if the water is being fed from cold storage tank and the mains hot water through the boiler. It might also help if there is a big difference between a cold mains supply and the lower pressure coming through the boiler supply. But if both are at the same pressure then the valve isn't really needed. Check it out first and if you need a valve then retro fit into the system, but don't go to the cost of buying one when you don't know if it isn't needed.
They are worth it. B&Q Warehouses sell them for about £20.
The hot and cold must come from the same pressure source. If a combi both from the mains. Where it is needed is when taps are turned on, or a toilet flushed. It instantly balances the hot and cold supplies, well a little glitch is felt, when say a toilet is flushed taking pressure from the shower. Some mixers have them built-in. You don't need a thermostatic mixer with them.
When fitting a combi, it is best to take the mains from the stop c*ck directly to the combi, uisng 22mm pipe, with no tee-offs on this run. At the stop c*ck install a tee and take a pipe to all the cold outlets. It may be worth installing a pressure reducing valve here to reduce the cold supplies. Just before the combi on the cold feed to it, tee-off and use this for the cold to the mixer. This reduces the effect of other outlets on the shower when turned on.
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