Check valves?

jcp

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I'm replacing a bath, basin and WC, with associated taps. Hot water originally came via an immersion heater (cold via a roof tank), but this was changed a few years ago to come via a Combi boiler (cold via direct feed).

Neither bath nor basin has any service valves, but the bath/shower mixer has a check valve on just the cold. The new bath tap is a simple replacement (two hole mixer plus shower), but the basin tap is a one hole joy stick (combined hot&cold).

I was planning on putting service taps on all taps feeds, but do I need to add check valves too (as one guide suggests)? And what about the WC?

I believe there are check valves immediately after the main stop tap and associated with the combi boiler (but could check).

Any advice would be very welcome.
 
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You need to add backflow prevention wherever there is a risk of stored/processed water entering the mains. Therefore a check valve at the basin is a must.

A check valve is not required on the toilet, as the air gap in the cistern should prevent any backflow.

The check valve on your boiler entry prevents the treated water flowing back into the cold mains from the boiler, but it will not prevent the same from happening at the mixer outlets, hence they are needed there too.
 
You need to add backflow prevention wherever there is a risk of stored/processed water entering the mains. Therefore a check valve at the basin is a must.

You already have an airgap at the basin, and any other taps which complies with the regs for stored hot water.
 
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I've never seen a basin tap with an outlet below the spill over level.
Some of the old bath taps yes, but they don't sell them anymore I think.
edit...Sorry just thought about it and see what you mean.
 
Thanks, but it seems the answer is unclear.

With separate taps, I see that the basin/overflow provides the airgap. With mixer taps (I'm not sure if the ones I have are dual or single flow), there is I suppose a slight chance of backflow. However, the hot and cold feeds are essentially at the same pressure.

My problem is I've got service taps to fit directly to the flexible tap hoses, and I'd need to change them if I need to put check valves in too (ideally between the service taps and the hoses - with short lengths of intermediate pipes too).
 
Also, maybe I do need check valves on the cold (mains), but should I put them on the hot too? I have seen that sometimes at mixer taps the cold can force back up the hot pipe giving tepid water at other sinks, but in my case the hot and cold should be at virtually the same pressure.
 
If it's an internal mixer you need a check valve on the cold, if external you don't. I think that's right now. :oops: :LOL:
You don't need one on the hot if it's off a combi.
 
Unfortunately it doesn't matter whether they're at the same pressure or not, where there is mixing of mains and another source then a check valve is required.

If it's getting difficult then consider putting one further back.

Yes, the air gaps are usually sufficient where separate taps are used. That includes both the gap between the taps, and the top of the basin.
 
Thanks again Sooey,

I'll check the basin mixer, but I don't think they give much information on the product sheet. I didn't see anything about check valves when I first read it, but I'll check again.

Actually, from memory, looking up the spout, I could see two holes in the ball valve, with more or less exposed of each as you move the joy stick. I think there was a short division between the two sides of the spout - and any mixing would have to happen in the very short open section.

But nevermind, I should probably change those service taps anyway.
 
And thanks mfarrow too.

The nice thing about putting the check valves after the service valve is they could be easily changed if necessary. They can all go behing the pedestal anyway.
 

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