Hi all,

Can anyone enlighten me as to what a "check valve" is and do I need one per feed for the h/c supply pipes to a bathroom sink monobloc tap?
The Screwfix catalogue says I need to use check valves for the flexible tap tails I plan to fit to replace the existing corroded rigid copper ones. Is that right? Both supply pipes come up from under the floor, BTW, and they already have isolators.

Thanks!

In article ,
writes:
Hi all,

Can anyone enlighten me as to what a "check valve" is and do I need one per feed for the h/c supply pipes to a bathroom sink monobloc tap?
The Screwfix catalogue says I need to use check valves for the flexible tap tails I plan to fit to replace the existing corroded rigid copper ones. Is that right? Both supply pipes come up from under the floor, BTW, and they already have isolators.

Thanks!

I think you would only need them on a basin mixer if one supply
is mains pressure and the other is from a storage tank, to prevent
cross contamination.

They don't work very well on low pressure supplies though - you
may only get a dribble through.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Dec 10, 12:19*pm, wrote:
Hi all,

Can anyone enlighten me as to what a "check valve" is and do I need one per feed for the h/c supply pipes to a bathroom sink monobloc tap?
The Screwfix catalogue says I need to use check valves for the flexible tap tails I plan to fit to replace the existing corroded rigid copper ones. Is that right? Both supply pipes come up from under the floor, BTW, and they already have isolators.

Thanks!

A check valve is a one way valve.
You might need one or even two on a mixer tap if the water pressures
were unequal (often happens.) and the hot and cold water are actually
mixed as opposed to having two separate spouts (as most have but not
all)
This stops cold water going into the hot water system and
so causing the loft tank to overflow with hot water.

On 10/12/2012 13:33, harry wrote:
On Dec 10, 12:19 pm, wrote:
Hi all,

Can anyone enlighten me as to what a "check valve" is and do I need one per feed for the h/c supply pipes to a bathroom sink monobloc tap?
The Screwfix catalogue says I need to use check valves for the flexible tap tails I plan to fit to replace the existing corroded rigid copper ones. Is that right? Both supply pipes come up from under the floor, BTW, and they already have isolators.

Thanks!

A check valve is a one way valve.
You might need one or even two on a mixer tap if the water pressures
were unequal (often happens.) and the hot and cold water are actually
mixed as opposed to having two separate spouts (as most have but not
all)
This stops cold water going into the hot water system and
so causing the loft tank to overflow with hot water.

The far greater danger is the possibility of 'contaminated' water which
has been in the loft tank getting into the cold supply in the event of a
mains failure.
--
Cheers,
Roger
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Thanks both,
the pressures may well be a bit unequal, but there's no loft tank. The tap is a single stem mixer. Do I still need these valves?

On 10/12/2012 14:25, wrote:
Thanks both,
the pressures may well be a bit unequal, but there's no loft tank. The tap is a single stem mixer. Do I still need these valves?


Where does it get its hot water from?
--
Cheers,
Roger
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On Monday, 10 December 2012 15:57:39 UTC+1, Roger Mills wrote:
On 10/12/2012 14:25, wrote:

Thanks both,

the pressures may well be a bit unequal, but there's no loft tank. The tap is a single stem mixer. Do I still need these valves?





Where does it get its hot water from?

--

Cheers,

Roger

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Condensing boiler in the kitchen.

On 10/12/2012 21:33, wrote:
On Monday, 10 December 2012 15:57:39 UTC+1, Roger Mills wrote:


Where does it get its hot water from?


Condensing boiler in the kitchen.

In that case, if hot and cold are essentially at mains pressure - with
cold coming direct,and hot via a combi boiler - I can't see how check
valves would serve any useful purpose.
--
Cheers,
Roger
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On Thursday, December 13, 2012 at 11:13:55 AM UTC, Roger Mills wrote:
On 10/12/2012 21:33, wrote:
On Monday, 10 December 2012 15:57:39 UTC+1, Roger Mills wrote:


Where does it get its hot water from?


Condensing boiler in the kitchen.

In that case, if hot and cold are essentially at mains pressure - with
cold coming direct,and hot via a combi boiler - I can't see how check
valves would serve any useful purpose.
--
Cheers,
Roger
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checked.

I think this may be useful if the combi boiler has a flow reducer which enables it to heat the cold water up. This would essentially mean that the hot water coming from the boiler will be at a lower pressure than the cold mains inlet.
Cheers.