Mains pressure not quite enough for kitchen mixer?

Postby sanderr2 » Tue Feb 15, 2011 7:31 pm

the cold water in our kitchen mixer tap has been slowly dying - it hasn't been great since we moved in but it had slowed to a trickle. The pressure at other mains fed taps seemed fine so I figured that the kitchen tap was past it's sell buy - washers etc.

I bought a new kitchen mixer tap online and connected it up only to find... no cold water at all!

I've checked the pressure all the way up to the tap and it seems strong. I put the cold feed onto the hot tap and voila - cold water. So I began to think there must be something on the cold side of the tap deliberately restricting the flow to balance the relatively low pressure hot coming from the combi against the high pressure mains fed cold.

I took the taps apart and sure enough, on the hot tap side there are two clearly visible holes into the final part of the tap assembly while on the cold side I can't see anything. Putting my lips to where the cold tap would be and blowing very hard finally yielded some flow (albeit my hot air) through the tap.

So my suspicion is that although the mains cold feed feels pretty decent it
isn't quite man enough to push through whatever valve exists on the cold side.

I thought that one way around this might be to drill a small hole on the cold side and enlarge it until the cold is flowing (but hopefully not too much to prevent any hot from flowing).

Presumably the alternative is a low pressure mixer tap - but with the relatively high cold water pressure won't that prevent successful "mixing"? Any wisdom would be very much appreciated.

Thanks and apologies for the lengthy post,
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Simply Build It

Postby stoneyboy » Fri Feb 18, 2011 5:48 pm

There is something wrong with the tap, return it as faulty.
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Postby jimbob22 » Sun Feb 27, 2011 12:07 am

A thermostatic mixing valve is designed precisely to cater for those differences in pressure and flowrate and are the only safe way to go where children and/or elderly are concerned.
Good shower mixers were sometimes sold in Aldi, or Lidl, for thirty sheets, a decent one should be found for under seventy today.
If your hot and cold taps do work and it's just the holes that have blocked, it will cost you nothing to drill a 6mm hole and give it a try, varying the mix with the taps.
Just remember, without a thermostatic mixer, the water temperature may be susceptible to large variations if other taps and outlets are also in use in the system.

Happy Piping :D
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Postby Perry525 » Thu Mar 03, 2011 6:37 pm

While water companies try to provide reasonable pressure, they do not always succeed.
In some areas water pressure is quite low at times of high demand and things like combi boilers do not always work.
Have you tried the mixer in the middle of the night?
Because of your location a low pressure set will work.
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