no hot water upstairs

[jimvmax]

Hello, hopefully someone can point me in the right direction with our hot water issue. I have scoured google without any real success.
I have an alpha intec34c boiler with solar and it’s 7 years old. Heating is fine. Hot water at kitchen tap is also fine, boiler kicks in with hot water icon when this is on. However, the kitchen tap has a higher pressure than any of the others.
The downstairs toilet sink and sink upstairs as well as the shower aren’t hot. The boiler doesn’t kick in when they are turned on, unlike the kitchen tap. My taps are mixer as is the shower. Could one these be the issue, or is it just cartridge style mixers that can leak cold water into the hot flow?
The Alpha engineer who I have a warranty and service plan sees no issue with the boiler but has changed the flow switch and pointed me in the direction of the thermostatic mixer valve. Which is not part of their system. Suggesting it may be blocked with sediment etc.
I have isolated the water, removed it and cleaned it but no real improvement. Maybe it has faulted internally? Other sites suggest the diverter valve. But the kitchen works fine and having the heating on doesn’t always improve the water temperature upstairs. Others the diaphragm and others the tmv.
I could change the mixer valve but if the kitchen tap is fine, can it be this? Or is it the case that it is the tmv but the good pressure of the kitchen tap masks the issue and is still asking for enough hot water to trigger the boiler?
Not sure if this would impact things but a new housing estate has been built across from us. If they are using the same water main I assume this would impact our water pressure. Could this be enough to stop our boiler being triggered when it was fine before? Any advice appreciated. Cheers. Jim.

 

[John D v2.0]

Sounds like the tmv is faulty not the boiler. When cold it should allow through pretty much 100% from the hot side with little resistance. Assume it's connected the right way round and wasn't removed previously for some reason.
Try temporarily bridging the incoming hot to the outlet to see if it solves it. If so then replace it.
I doubt the new water main caused it unless you have issues with other taps.
If the problem only occurs with all outlets downstream of a given fitting only, the problem has to be there.

 

[jimvmax]

Thanks for the reply. I will change the tmv and hope it cures it. My issue is, why is the kitchen tap ok, is it not fed via the tmv?
All the other house taps and shower are effected. Only the kitchen tap is hot. Not sure what u mean by bridging the incoming hot to the outlet. I’m a newbie to plumbing.

 

[John D v2.0]

My issue is, why is the kitchen tap ok, is it not fed via the tmv?

Presumably not

Not sure what u mean by bridging the incoming hot to the outlet

The tmv takes hot and cold and outputs warm.
I meant remove the tmv, then connect the incoming hot up the output. And cap off the cold.
Then that will prove the tmv being faulty before you buy a new one.

 

[Deleted member 267285]

Are you able to isolate any of the cold feeds including the shower? If so, then you may be able to do this and run a hot tap and see if it’s any better. Is the stopcock fully open?

 

[jimvmax]

Thanks again. Sorry, I understand how the tmv works. But not how to connect the hot to the output and blank the cold. Well I know what u mean. But not how to do it. I may just have to buy the tmv and hope it sorts it. Appreciate ur replies. Thanks.

 

[jimvmax]

The taps do have isolators. Don’t think the shower does. If i isolate the hot and water still comes out then it’s coming from the cold feed. Think that’s what u mean.

 

[John D v2.0]

Thanks again. Sorry, I understand how the tmv works. But not how to connect the hot to the output and blank the cold. Well I know what u mean. But not how to do it. I may just have to buy the tmv and hope it sorts it. Appreciate ur replies. Thanks.

Can do if it's convenient and the cost isn't the main issue for you.i only suggested that because you'd had the thing out to clean so i thought you might be happy to rejig the pipe work

 

[jimvmax]

I’d rather not spend it John. But it’s something I can do. I don’t have the parts to try ur suggestion. Although it sounds as if it would have worked. Cheers. Jim.

 

[John D v2.0]

If it worked with it bypassed then that would mean the valve was at fault and needed replacing anyway.
You could always buy it somewhere with a good return policy eg screw fix or Wickes and then just take it back if it doesn't fix it.

 

[Deleted member 267285]

The taps do have isolators. Don’t think the shower does. If i isolate the hot and water still comes out then it’s coming from the cold feed. Think that’s what u mean.

Opposite, turn colds off and open a tap on one and see if that fires up your boiler.

 

[jimvmax]

Ha ha. Cheers. I wrote cold. Then confused myself and edited it. I’ll try it now. Thanks.

 

[jimvmax]

Still only fires up with the tap in the kitchen. Not sure if it’s on a different feed as I said. But no other tap will make the hot water kick in on the boiler. However, if I turn a tap on and a shower it kicks in. So may be then there is enough demand for hot water to trigger it?
I’ll change the tmv tomorrow as it’s £40/£50. I’m not 100% that it will fix it, but worth a try. Cheers for the replies. If it doesn’t work, I’ll get a plumber to have a look as the Alpha engineer said the boiler was fine.

 

[Deleted member 267285]

Did you check the stopcock is fully open?

 

[jimvmax]

Yeh, I have had it turned off to remove the tmv to try and repair/clean it. But reopened it once I refitted it. As I said, kitchen tap has really good pressure and is enough to get the boiler to kick in. So no issues at stop cock. Cheers.