Kitchen Mixer Tap not able to mix very well

[sotal]

Hi,

I've just put a new sink and mixer tap in the kitchen (replaced a mixer) The new tap said it was only suitable for use with mains cold and tank hot which is what I have got.

The mixer has two seperate handles, when I open the cold on it's own it's fine loads of preasure, if I open the hot on it's own it's OK, but if I open them together then I only get cold and it's less presure than cold on it's own. If I then put the hot on, on it's own I get cold water for a good while.

So I believe it's forcing the cold water up the hot water pipe which I'm sure can't be good for the system, I can just about get it to mix by only opening the cold water a tiny amount.

How would I go about fixing this? My immeadiate guess is to put some kind of non return valve on the hot water pipe. I would have thought that would fix the water going up the pipe issue but I pressume mixing wouldn't be any easier?

Any suggestions? It's not the most important thing ever as the dishwasher is used most of the time, it's mostly just used for cold drinking water and rinsing things

 

[sotal]

Any ideas?

 

[Softus]

if I open them together then I only get cold and it's less presure than cold on it's own. If I then put the hot on, on it's own I get cold water for a good while.

So I believe it's forcing the cold water up the hot water pipe

That's rather strange, because it implies that the resistance of the spout is greater than the pressure of water from the hot service.

Can you remove the spout filter/aerator and repeat the exercise?

 

[sotal]

It has a bit of fine mesh on the spout but it doesn't look removable, but yes it does seem that the resistance of the mesh is greater than that of the hot water flow.

I've found some water regs which state I should have a check valve on both anyway - so I'll pick a couple of check valves up and see if that cures it.

Just seems strange that the old mixer worked perfectly, the only difference was that the old one were full turn taps and the new ones are quarter turn taps.

Also when I removed the old sink I installed isolation valves on both the hot and the cold pipes so that I can turn it off easier for any maintenance. Whilst looking yesterday I noticed that the isolation valves have an arrow on the side of them. I've put the cold on the right way but the hot is the wrong way round - would this cause any problem? From looking at a spare one I can't see that it would cause a problem

 

[sotal]

Any suggestions/comments

 

[Softus]

Whilst looking yesterday I noticed that the isolation valves have an arrow on the side of them. I've put the cold on the right way but the hot is the wrong way round - would this cause any problem?

Please describe the valve in more detail, or post a photo of it, so that I can understand the impact of fitting it the wrong way round.

 

[JPC]

either way. its sounds as if the cold is pushing the hot back up the pipework .

buy a diff tap with seperate tubes (dont mix in the tap body)..

or a pressure reducer on the cold might work ??...to try and match the hot pressure.

or a pump on the hot supply

 

[Softus]

either way. its sounds as if the cold is pushing the hot back up the pipework .

Yes, but have you ever known that to happen with a kitchen tap?

buy a diff tap with seperate tubes (dont mix in the tap body).

I'm curious - have you ever seen a kitchen tap that mixes water in the body?

 

[sotal]

Thanks for the replies.

I've just had another play with it and I'll try to give as much info as possible.

It's the kitchen sink, it's quite a fancy tap which is mounted on the worktop rather than the sink. It came with two flexible tails which screw on to the tap with 10mm nuts, and the other end is the same thread as a standard 15mm pipe connector.

The old sink was connected with the thin copper pipe and was connected to the 15mm pipes with a soldered flair which then connected with a 15mm straight connector.

I switched the water off, removed the old sink, removed the two straight connectors and replaced them with cheap ball type isolation valves. I think they were these ones:

http://www.screwfix.co.uk/prods/52623/Plumbing/Brassware/Isolating-Valve-15mm-2Pk#

If you zoom in on that picture you can see an arrow on the side which I presume is supposed to go with the flow of water. On the cold I have that going with the flow, but on the hot I accidentally installed it the wrong way round so the arrow points back against the flow - but looking at them I can't see that this would cause a problem.

I then attached the flexible tails to the isolation valves and turned it all back on.

There is enough pressure from the hot water tap - just like before and there is a lot of pressure from the cold tap (seems like more from the cold but it's probably just the way it comes out) I have found that if I don't open the cold more than half way then it mixes fine, but any more than half way and it goes just cold and appears to push cold up the hot pipe. I guess the mixing is actually OK when you get used to it and I guess you notice more because the old taps went all the way round (maybe even more than once) so it was more gradual, wheras the new ones are only quarter of a turn.

I looked more at the airator to see if it could be removed but I can't see how without damaging it.

So I think a check valve on the hot will cure my problems and I will have to presume that the airator restricts the flow a bit more than it should??

So do you think I need to turn the isolation valve round or should it be OK?

 

[Softus]

...on the hot I accidentally installed it the wrong way round so the arrow points back against the flow - but looking at them I can't see that this would cause a problem.

It's likely that it could result in a problem only when the valve is shut, but I'd be tempted to correct it now rather than regret it later, since you merely have to shut off the hot service and change the valve around (i.e. it's quick and easy).

...I guess you notice more because the old taps went all the way round (maybe even more than once) so it was more gradual, wheras the new ones are only quarter of a turn.

That would certainly highlight the problem.

So I think a check valve on the hot will cure my problems...

A check valve will [probably] stop the cold backfilling the hot service, but it won't do anything to promote mixing, and you'll be left with balancing the pressures using the hot tap.

...I will have to presume that the airator restricts the flow a bit more than it should?

Well, maybe. I think there are only two recommended ways out of this:

1. Replace the tap (as someone already suggested) with one that doesn't mix the water until the end of the spout.

2. Fit a pressure limiting device on the cold supply to the tap.

So do you think I need to turn the isolation valve round or should it be OK?

Partially closing the ball-o-fix valve on cold supply to the tap is not a supported thing to do with a cheap spherical valve, and will shorten its life.