Check valve for shower mixer gravity hot water mi

[RayPlumb]

I have a shower mixer that was on mains cold (3.5 bar) and gravity hot +/- 0.15 Bar ( a Bungalow). I fitted a Pressure reducing valve to the cold to equal the pressure. Also to comply to water regs a check valve on the cold and hot. But with little gravity pressure on the hot the check valve just stopped the flow and no hot??
How do I get round this and still comply with regs. If I run hot and cold off gravity then I will have equal pressure but still need to put check valves which will stop the flow...In the loft all the pipework is in steel so just tapping in up there will be a big job...
Any ideas ??? What are my options to tell my client as the mixer shower used to work for about 6 years??? Presume the water board has upped the mains pressure reciently

[Bernie2]

Hi! Ray!

I know bungalows are tricky over head loss. But one or two points I would check out would be.

The Water Regs are a bit hazy about some aspects of fitting a shower, but the DHW is usually classed as a Cat 2 risk and so only a single check valve not a double would be required on the hot side.

I would also check to see if the shower already has an internal single check valve and by putting another one on the supply its been made into a double check, which has increased the resistance enough to stop the hot flow.

The cold main is protected by the double check you have already fitted.

If you put a shower hose capture hook on the shower hose so it doesn't drop in the bath, basin or toilet that maybe enough to comply with the regs.

Back flow down the hot should not be a problem, as you have put a pressure reducing valve on the main, so in the shower, both pressures should be balanced and the hot has got a single check valve on anyway inside the shower, so even if the main backed up the hot, which it shouldn't, the storage cistern should have a type A air gap to prevent it going down the main in the cistern.

Anyway, Please don't take my word for it have a look at WRAS 2005, Water Fittings and Materials Directory, Amendment 18 June 2009. Its interesting, scroll down to the bottom area. At least it gives you some kind of official reference to work from.

Hope this helps.

[RayPlumb]

Thanks Bernie
Tried the shower hook to keep the rose out of the bath. But the client was having non of that as it was to wash her hair with..
The Mixer taps do not have any check valves built in on the hot or cold.
The mixer part of the shower has a negative pressure diverter valve to the hose( the type you open the taps for the bath, push down the valve and it diverts to the shower rose. Switch off the tap and the diverter pops back up). Would this be considered as check valve...? As any loss or reverse in pressure and the diverter valve divers to the bath spout.
Any one think otherwise please let me know.
Thanks...

[Bernie2]

I assume its got a shower hose, air break union stopping and backflow down the hose?

Its all a bit of a problem really isn't it?

If the hose can fall in the WC it comes under Cat 5, which involves a whole lot more backflow prevention.

I doubt if you followed the regs you would install that type of shower now where it is in relation to the distances from other fittings.

But if putting any kind of restriction on the hot supply causes it to stop, then what options are left open to you?

You could replace the mixer, but they don't seem to want that. You could put on a retaining hook but they don't seem to want that.

All you can really do is protect the mains water to standards and inform them about the rest.

Good Luck