Cold water from hot water tap

[Clarky100]

Hi, ive had an issue a few weeks where my combi boiler cant heat the hot water to the max temp. I noticed now that i also get cold water from my hot water tap in the bathroom sink when i run my bath at the same time. When i do this, the water from the bath tap is scorching. When run individually the hot water isnt hot from any taps or shower in the house. The taps in the kitchen, bath and downstairs toilet are mixers as well as the shower unit. Running the hot tap in the sink, which gives cold water, is the only way i can get hot water in the bath. Not sure if this was a coincidence but I had my stopcock changed as it was leaking just before this happened. Ive also isolated all mixer taps except the shower from the system but this hasn't cured it. Boiler is a Combi Main 30 HE. Any ideas at all would be greatly appreciated. Thinking its either the shower passing cold to hot, a boiler issue or a flow issue on the system???? Thanks.

 

[glenno1]

Turn down your stopcock a bit and see if this helps any

 

[Clarky100]

Hi, Yeah I tried that too, but that didnt make any difference either.

 

[glenno1]

does the combi fire up when a single tap is opened

 

[Clarky100]

Hi, do you mean the single tap in the bathroom? Ill have to check. I think it must do as the water does warm up but ill check tonight.

 

[Shower Engineer]

Possibly debris in hot water NRV (non return valve) of shower mixer? This could allow cold water to mix with the hot water.

 

[Clarky100]

Possibly debris in hot water NRV (non return valve) of shower mixer? This could allow cold water to mix with the hot water.

Thanks, i guess thats possible. The shower is quite old. How would i check that, by taking apart the mixer unit in the actual shower?

If this is the case, how is that making the hot water tap in the bathroom sink give out cold water when the bath hot water tap is running scolding hot?

Cheers

 

[Shower Engineer]

Water will take the easiest route so if you have shower then basin then bath then boiler the water getting past the NRV can flow to the basin tap while the water flowing through the boiler can go to the bath tap.

If you post a picture of the shower or let me know what make and model it is I amy be able to say if this is a possible cause.

Hope that helps.

 

[Clarky100]

Water will take the easiest route so if you have shower then basin then bath then boiler the water getting past the NRV can flow to the basin tap while the water flowing through the boiler can go to the bath tap.

If you post a picture of the shower or let me know what make and model it is I amy be able to say if this is a possible cause.

Hope that helps.

*** Thanks. Ill get a pic of the shower taken later today and post it up. Will also try to see what make and model it is.
Cheers.

 

[Clarky100]

Hi Please see the above photos of the shower. Cant seem to see a model number listed anywhere.
Hope this is enough info.
Thanks

 

[Shower Engineer]

That is not a shower I know and being a concealed valve makes it a bit more tricky. Does the shower work ok? Is the temperature of the shower ok? If yes then we could be on the right track. If no then the showewr is probably not the culprit.

If you have access to the shower pipes, within an adjacent cupboard or roof space then you can test by doing the following. Run the shower until it gets hot, feel the hot pipe to the shower, it will be hot! Now run another hot tap, does the hot pipe to the shower become cold? If it does then cold water is passing through the mixer. You may also find that turning the mixer fully cold or fully hot stops the problem although this is not a permenant solution.

Hope that helps.

 

[Clarky100]

Hi, no the shower has the same problem. I doesn't get hot either and is luke warm like the other taps, even when the shower unit is set to full hot.

Just tried the following.
1) Ran shower and its warm. Then sink tap (non mixer) which is scolding and shower goes cold.
2) Ran shower again this time with bath mixer set to hot. Bath is scolding and shower is cold.
3) Then I just tried the shower now with it set to fully cold and its still warm!!!! So the mixer unit doesnt seem to have any affect to the temp. That doesnt seem right does it??

Im not sure I can get access to the pipes as they are all concealed.

The other thing I noticed is that boiler doesnt get up to 80 degrees on the gauge anymore when it used to easily before this started. It can only get up to 70.
The central heating is fine though and heats normally.

Thanks

 

[glenno1]

Sound like a pressure to shower head problem

 

[Clarky100]

Hi sorry, how do you mean a pressure to shower head problem? Thanks

 

[Shower Engineer]

Ok back to basics. Are you able to identify the hot water pipe at the boiler? Can you let us know if this runs hot when you get cool water from a tap?

 

[Clarky100]

Hi yes i can confirm the hot water pipe from the boiler is hot. Ive also discoved the following.

I Traced hot water pipe from boiler to kitchen sink and see where it diverts upstairs. When i run the hot water tap in kitchen, the hot pipe going upstairs is cold, the pipe from the boiler is hot and the pipe to the kitchen sink (where the above 2 meet) is luke warm....so confirming hot and cold is mixed.

I then traced the pipes going upstairs to under the bath and its the same thing. Now here where the pipes divert again is where they go onto the shower. When i run the bath tap on hot, the hot water pipe is hot, but then i can feel cold water comng back to the bath on what would be the hot water pipe to the shower, giving luke warm water on the mixed pipe to the bath tap.

The fact that the shower temp dial also makes no difference to the temp on the shower and the above says to me its the shower causing this.

What you think?

Cheers.

 

[BLOD]

Fit isolation valves to any mixer taps & shower valves. Then isolate everything and test one by one.
Hopefully you'll find the culprit

 

[Guest123]

Fit non return valves to the hot and cold supply pipes to your Thermostatic mixer shower.

 

[Clarky100]

Fit non return valves to the hot and cold supply pipes to your Thermostatic mixer shower.

Hi thanks. Al the taps have isolation valves which i tried and pointed in the direction of the shower, so yes the next step Is to check the shower. Problem is the pipes are hidden in the wall so unsure if they have no non return valves, or they do have non return but are stuck open.

Cheers

 

[Gmaservices]

I've just had this issue on a job all hot outlets running cold except if you ran them all, then they would get warm. It all pointed at the shower!
I just happened to look be hind a washing machine which was a cold feed only. The bloke had put a y on the back of the machine and connected hot and cold to it.
Quick replumb of it and it all worked fine!

 

[Guest123]

It's the hot and cold mixing incorrectly in your shower, isolate both supplies and fit non return valves on each.