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Hi everyone, I am looking for advice as under my kitchen sink their are two pipes, the cold water feed and hot water feed, the hot water feed has a check valve/NRV fitted on the copper pipe (I am not sure which kind of valve it is but it has an arrow on it) but the cold water feed pipe doesn't have a check valve (NRV) but just a stopcock.

Do I need a check valve on the cold water feed as well and if so is it better to have check valves or non return valves installed?
Any info would be great thanks

(I have a combi boiler and the water which comes into my top floor flat is all via the mains)


Yes fit one.

A check valve is a non-return valve and vice versa. Just two names for the same thing.
Thank you much appreciated, also is it enough to have a NRV on the main cold water feed pipe which is under the kitchen sink or do I need them in the bathroom as well?
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I have a cold water feed pipe in a utility cupboard, a plumber has said that I don't need to fit a NRV under the sink pipe but NRV needs to be installed on the CWF pipe which is in the cupboard, is this right? Also the CWF is a red gate valve on a pipe.
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Check valves should be fitted at the source of the possible contamination i.e. near the mixer tap, not somewhere up the pipework. I'm assuming you have mixer taps that allow in-body mixing to take place and that that is the backflow risk you are concerned about? If both pipes are at roughly same pressure, then no check valve is required. If pressures are unequal then both sides should have a check valve. People will tell you the hot side doesn't need it, but my understanding of the legal situation has been confirmed both by WRAS and by a Water Regulations Officer in the course of his work (i.e. officially) of Dwr Cymru (Welsh Water).

In practice, if pressures are very low (gravity systems), you may find a certified check valve is reluctant to open. Then I leave it to your conscience of whether to fit the certified device and have it jam shut on a regular basis, fit a swing check valve or other low-pressure check valve that doesn't meet the regulations, rip the spring out of the check valve, or omit the check valve altogether. If you find a certified device that works really well at low pressures, please do let me know.


Check valve or NRV on incoming cold water mains.

You are permitted to poison your own household but not the neighbour's with whom you are connected to with the mains.
That's my understanding of the rule!


Not in the UK. UK requires backflow protection at point of potential contamination.

Lack of backflow protection on hot side can allow cold water into the cylinder feed cistern which can then (a bit tenuous here, but it's what Dwr Cymru tells me) potentially undermine the air gap at the float valve and thus risk contaminating the mains, or lead to overflow and thus wastage of water (another way to fall foul of the Water Regs).

But now it's my word against Oz's and why should you believe me? Who's to say I'm not wrong? If in doubt, phone water board and ask to speak to water regulation officer. Or contact WRAS which has a duty to provide free information to allow people to understand how to comply with the law. My experience is the water industry is unable to police every installation in the land and is always very happy to assist if you are trying to be compliant and want some advice.


That the hot and cold are at roughly the same pressure. I.e. both mains pressure (mains cold, combi boiler or unvented cylinder hot) or both gravity fed (cistern in loft).

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