Bad taste in cold water - unvented system

[robinbetts]

Hi all,

We have a very similar problem to that described in this post:

//www.diynot.com/diy/threads/rubber-taste-in-cold-water-unvented-cylinder-system.355821/

Our cold water supply runs in our loft space. It goes into a valve of some sort. I was under the impression that it was some kind of pressure reducing value, but it looks a lot like this... http://www.advancedwater.co.uk/products/640-388-0002(350W).jpg but without the 15mm outlet on the left. The outlet on the bottom is connected via a flexi hose to an expansion vessel. On the other side of this valve the pipe splits and goes to the cold inlet of the unvented cylinder, and our kitchen tap (plus washing machine, dishwasher, utility sink tap and toilet).

Here's a diagram of the setup:

The other aspect is that whenever water is drawn off from the far side of this valve, it makes a loud sound like something is spinning up, and it rattles and kicks the pipes about, which can be heard throughout the whole house. Is this to be expected with this kind of valve?

From reading the above referenced thread, I'm assuming that either this setup is incorrect, and potable water shouldn't have been taken off after the valve, or that the valve and/or expansion vessel is faulty. Can anyone enlighten me before I speak to the plumber who installed it, so that I can try and know what I'm talking about

Many thanks,

Robin

 

[flameport]

The other aspect is that whenever water is drawn off from the far side of this valve, it makes a loud sound like something is spinning up, and it rattles and kicks the pipes about, which can be heard throughout the whole house. Is this to be expected with this kind of valve?

No, that should not be happening.

What colour is the expansion vessel?

 

[robinbetts]

The expansion vessel is white.

 

[Agile]

It seems generally correct based on the limitations of your basic sketch.

My first test would be to measure the air charge on the expansion vessel. But any work on unvented cylinders should only be done by those holding the appropriate G3 qualification.

Then I would want to measure the static supply pressure and the pressure at the cylinder inlet.

You complain about a rubber taste in the cold water. But you should only be drinking the direct cold mains at the kitchen tap.

Tony

 

[robinbetts]

Thanks Tony,

Is that to say then that the kitchen tap should have been teed off before the valve, and not after it with the hot water cylinder?

Thanks

 

[Agile]

The kitchen tap should be direct from mains water before the PRV.

The cold output is for things like showers and basin taps where the same pressure for hot and cold is beneficial for mixing taps etc.

Tony

 

[muggles]

The kitchen tap should be direct from mains water before the PRV.

The cold output is for things like showers and basin taps where the same pressure for hot and cold is beneficial for mixing taps etc.

Tony

Piffle, there's absolutely no reason why the cold to the kitchen tap shouldn't be run from the PRV.

OP, not sure about the bad taste but the gate valve you've drawn on the supply to the cylinder should not be there. Do not ever turn this off, as doing so will severely compromise the safety of your cylinder. Also, gate valves are designed for low pressure systems only. In other words, you'd be better off getting rid of it.