Non return / Double check valves and Monobloc Mixer taps

Gnasher_06 · 8 May 2006

Hi,

On my search for a replacement monobloc tap, I have a question to ask please.

When should non return valves be used and are they the same as a double check valve ?

As some of the taps seem to come with them already fitted to the hot side.

A lot of the mixers on the market seem to mix the water in the tap body.

As I have found to my cost, the 'posh' ceramic quarter turn taps are no good for our kitchen as our Hot water pressure is way too low. (Comes from having the water tank on the first floor)

SparkyMarky · 8 May 2006

Gnasher_06 said:
Hi,
As I have found to my cost, the 'posh' ceramic quarter turn taps are no good for our kitchen as our Hot water pressure is way too low. (Comes from having the water tank on the first floor)

Hmmm, me too! Currently I've got a lovely shiny new monobloc mixer in my kitchen, which takes about five minutes to fill the washing up bowl with hot water! I do however have a Grundfos UPA 15-90 booster pump ready to fit, which hopefully will solve the problem.

I think non-return valves have to be used to prevent hot water being syphoned back into the cold water main. I think it's a water by-law. IIRC you're also supposed to fit them to outside taps to prevent water from hoses being syphoned back into the mains...

Paul Barker · 8 May 2006

domestic hot water is a low risk only a single check valve is required, should be included in mixer taps.

Proper outdoor bib taps have the necessary valve built in, don't use a run of the mill bib tap. You can buy full outdoor tap kits for £12 or so in many places.

Put service valve on so it's easy to isolate during periods where freezing is likely.

Paul Barker · 8 May 2006

If your hose is full of water and has it's end in your fish pond, and the water board do some work on the mains so turn it off, and if you suddenly decide to turn on your outdoor tap, the negative pressure may facilitate the syphoning of your pond into your cold water supply, it might by a very slim chance even reach your neighbours water supply. When supply pressure is restored, if you are stupid enough not to run off a small amount of water before you use it (though the mud which comes from the water boards pipes should give you a hint, the first water to come from your tap will be from your pond.

This unlikely combination of events has given the folk with big foreheads something to justify their existence behind a desk.

ChrisR · 8 May 2006

Exactly that happened in the US, I woz told on my Water course. Whether there's any truth is a different matter of course!

You need a check valve on the cold to stop HW going back down the main, and one on the hot to stop CW going up the pipe. The ones built in to taps are ridiculously small, so I have hoiked them out and put bigger ones in the supply pipes.
If the waters are kept separate all the way to the end of the spout there's no chance of backflow so you don't need the valves, but the design is usually then such that the low pressure hot has to go up the middle of the spout in an even tinier tube. I reversed my kitchen tap so the hot goes up the larger annulus and the cold the wee tube in the middle. It means Hot is on the right but , er, so what?

Paul Barker · 8 May 2006

Hot is on the right more often than not where summer time chefs do the plumbing out of tourist season.

Agile · 8 May 2006

Paul, the Water Regs have changed!

With an outdoor tap you need a double non return and an isolation valve on the INSIDE of the property now.

The bib taps with a built in valve are only suitable for indoor use now.

Tony

Gnasher_06 · 9 May 2006

So just to confirm,

A single check valve will do, but is needed on both Hot and cold....

Thanks for the replies, If I ever want an outside tap then I'll know what to do too.

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Non return / Double check valves and Monobloc Mixer taps

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