Of pressure reducing valves, combis & showers...

[Scott M]

Hi all,

As part of a house renovation I'm putting in a combi and a thermostatic shower in the bathroom. Now the shower I've bought (ToolStation £69 job, forget the make) gives the pressure range as 0.3 to 3bar and I suspect the water main pressure is higher. Short of getting a different shower (why people won't list the max pressure of these things) can I just fit a pressure reducing valve (eg

on the incoming main and feed everything including the combi from that?

Also, do reducing valves affect the flow badly? I'm vaguely considering fitting one at home as I'm about the 2nd house off the main feed and get a viscious flow rate and ~10bar which makes me eternally wonder that the plumbing isn't blown apart.

Ta, Scott

[Ed Sirett]

If your incoming main is truly 10bar then a PRV is called for. Almost everything will be having a hard time (including the boiler which may well be rated for as little as 8 bar max). Taps will jam and spit and wear out quickly, cisterns will be whistling as they fill, they will probably need new washers frequently. If you truly have 10 bar then I don't think you'll need to worry too much about the resistance put up by the valve.

[Scott M]

It's certainly well over 7bar - the gauge I had only went up that far - but there was still plenty of scope for going higher (I'd only cracked the tap open slightly to let it rise slowly.) I replaced the main toilet cistern with a Fluidmaster valve as it did whistle awfully and it was lovely and quiet afterwards. Trouble was it filled the cistern in 12sec flat and, finding the overflow couldn't cope (surprise), I turned down the ball valve which made a whole new range of noises. A bit of tweaking made it play an acceptable note but it's not ideal.

The boiler is for a different property but again there's good pressure and flow so unless there's a good reason otherwise I'll shove one on there too.

Scott

[Christian McArdle]

Always fit a PRV for any system with more than 6 bar pressure. Consider one for between 3 and 6 bar, depending on how the system performs. Don't fit one below 3 bar.

Also, if you have an unvented cylinder, you must have one to protect that and there is usually a cold outlet that can provide a pressure balanced cold supply.

Christian.

[Scott M]

Thanks for that - that sounds like a good rule of thumb.

Not got one of those - might go for a heat bank and exchanger at some point though.

Scott