Non Return Valves.

[d4n]

I am planning the fitting of a new bathroom in our home. It isn't a straight replacement so I will need to renew the piping to the fittings.

When I remove the bathroom I will strip the pipes back to the 22mm hot and cold stop valves and start fresh. From there I will be using JG Fast fit plastic piping and fittings.

The cold will be mains fed, The Hot is pumped gravity fed. In a few months we will be moving to a mains combi boiler for the hot which should balance the pressure.

When re-plumbing the bathroom I was going to use non return valves on the hot supply to prevent the cold water surging down the hotpipe

My questions are:

1) Would I need non return valves on the cold supply as well?
2) Would I need to fit non return valves before each mixer (Bath / Shower / Basin) or could I fix one to the supply before it branches?
3) When we move both supplies to mains pressure should I remove the valves?

Thanks
Dan.

 

[denso13]

The cold won't go into the hot water pipework even though it's at a higher pressure. What taps will you be using?

 

[Michael01474]

not to disagree but I've recently had the mother of all nightmares with what appeared to be a boiler problem - we had no hot water even though the boiler appeared to be working fine. It turned out to be the shower valve. One of the non return valves wasn't working and we were getting mains cold water into the hot circuit. I won't pretend to advise you on the plumbing specifics as I have no expertise in that area - just thought I'd share an experience.

 

[denso13]

Things sometimes go wrong but there is no requirement to fit non return valves, most if not all manufacturers don't specify them.

As for taps the water doesn't acually "mix" in the taps, well modern ones anyway, so it isn't a problem there either.

I realise it doesn't cover every eventuality, but that is the way it's done (usually).

 

[d4n]

The fittings have all been purchased from the bathstore.com

Bensham Mono basin mixer.
http://www.bathstore.com/_application/bathstore/products/taps/bensham-basin-taps/index.html

Edwardian Thermostatic Shower Valve.
http://www.bathstore.com/_application/bathstore/products/showers/shower-valves/index.html

Extrafill bathfiller.
http://www.bathstore.com/_application/bathstore/products/baths/bath-filling-wastes/index.html

for the sake of £6 per pipe £36 all in. I'm inclined to fit valves regardless.

 

[denso13]

Go for it if you want but it is pointless.
Remember too, the hot water flow will be restricted by fitting them, so a noticable reduction in flow rate could occur.

 

[d4n]

Thanks Denso for the advice.

 

[breezer]

i took some of them back once, wrong size, bloke would not take them, why i asked, becasue they are "non return" valves

 

[denso13]

Yep thats another problem if you get the wrong.... wait.. I see what you did there

 

[ChrisR]

ALL mixers and mixer taps require backflow prevention unless they're the sort where the flows are kept separate right to the end of the spout, which you see on some kitchen taps.

Really small non return valves as fitted to some mixers can restrict the flow, but the pipe-sized ones won't affect pumped or mains flows significantly.

 

[denso13]

The backflow problem is not so much hot/cold mixing in taps but the danger of contaminated water flowing back through taps/pipework.

A propely designed system has no need for check valves everywhere as described here http://www.defra.gov.uk/environment/water/industry/wsregs99/guide/section6.htm and http://www.wras.co.uk/Directory/IRNs.asp section IRN 109

There will be some situations, eg shower hose lying in bath water, where additional measures may be necessary but it is down to design, and proper air gaps.

 

[bster]

If the water mixes within the tap body then you must put a check valve on the cold and its wise to put one on the hot to prevent back filling of the hot water system. If (as mentioned) you are using a bi-flow mixer then there is no need for backflow prevention (if the tap gap is maintained and any shower attachement is unable to fall below the spill level of a bath\bidet\WC etc)

 

[denso13]

Not according to the water regulations or manufacturers instructions. But hey, whadda they know

 

[bster]

Denso - whats not according to Water Regs?

 

[denso13]

Check valves on mixers, if they are properly installed. Nothing to stop you if you want, but there is no requirement.