Shower mixer cold water feed back? Help and advice required

[rob99]

Hi, I'm hoping someone can offer me some advice.

I think I know what the problem is but I could do with some clarification by someone with a little more knowledge!

I have done a diagram that I'll attach below to try and explain things a little more and I'll try and attach a picture of the shower mixer tap too!

First an explaination.

I have fittted a new shower in the ground floor of my house.

Since fitting it I have noticed the hot water on the first floor is only just warm enough to shower/wash in.

When the shower is run on its coldest setting the water on the first floor is lower pressure but piping hot!

I think that perhaps when the first floor hot tap is run the cold pressure is pushing back up the hot pipe that leads down to the shower and coming into the first floor hot supply... but this is simply a calculated guess!

Here are the pictures to try and explain!

Rough plumbing diagram:


And the shower mixer tap is almost identical to this one:


Thanks in advance for any advice you can offer me!

Rob.

 

[chrishutt]

Turn off hot supply from combi. Does any water continue to flow out of hot taps? If so this is cr5ossing over through the shower valve (or other mixing valve). There should be check valves built into the shower valve to stop this, but the hot inlet one may have failed.

 

[rob99]

Ok, now my lack of knowledge when it comes to boilers will show!!

It's a Vailant combi boiler. I have not idea which is the hot suply valve I should be turning off, and am I likely to do any damage by doing this??

I have attached a picture of the boiler pipework. If someone could point the correct valve out to me perhaps??

Thanks again.
Rob.

 

[chrishutt]

Turn off the cold inlet valve, which is just to right of gas connection in the middle. By the way, which clown installed that boiler? What a mess he made of the pipework.

 

[rob99]

Sorry to be a pain but can you confirm that this is the correct one??



Thanks again for your help.
Rob.

 

[chrishutt]

Yes, there's a label on the underside to confirm it.

 

[rob99]

well I finally got a minute to test and yes, when I turn off the supply to boiler I still have water running though the hot taps.

Is there likely to be any other explaination for this other than the shower mixer that we are assuming it is??

Thanks,
Rob.

 

[rob99]

Thanks for all of the advice.

Faulty shower mixer now replaced and all is good!