Unvented cylinder not providing hot water to sinks,only showers

[rado16v]

Hi John, no idea. What should I be looking for?

We have a water softener too that feeds the cylinder.

 

[Johntheo5]

Can you post a photo of this softner with all attached pipework, it might include a PRV something like the one below.
Also, in your LH photo, post #1 you will see the cold water inlet right at the bottom of the cylinder, it has a drain cock on it, follow this back and see if it also has a PRV.

 

[rado16v]

Indeed it does have a prv when I follow the cold water inlet, pic attached.

There's nothing at the water softener end.

Thanks

 

[Johntheo5]

You have a balanced cold off that combination valve set.
Where I have marked "cold mains cold feed", see if there is a isolating lever valve a bit further back between it and the water softener, if so, close it and then check for no cold water from any of the mixer valves.

 

[rado16v]

Ok I found and closed it. It's by the water softener and stops all the cold water in all the taps. This time the kitchen tap was hot and did not dip. I guess that would make sense as there's no cold water at all in any of the taps now, in the kitchen we have a filter type tap for just drinking water from the mains.

Where you have balanced cold, that pipe goes to an isolating valve

 

[Johntheo5]

The valve you closed supplies the water to the cylinder so once shut then you shouldn't have hot or cold (balanced) water, you might get a few litres of hot water for a few minutes. Any way reopen this valve and shut the balanced cold isol valve and turn each mixer to fully cold and check that no water flows from them.

 

[rado16v]

I closed the mains cold water feed and ran all taps until hot and cold water stopped, about 5mins.

I then shut all the taps, opened the mains cold water feed and closed the balanced cold feed and ran cold water only on all the taps and they all are running cold water and no signs of stopping.

Does this mean bad prv?

 

[Johntheo5]

No, nothing to do with the PRV.
IF the isol valve is on the balanced cold after the PRV and (the isol valve ) not passing then it can only mean that none of those taps is fed from that balanced main.

 

[rado16v]

Some more pics, yes the isolating valve is on the balanced cold pipe with red handle.

 

[Johntheo5]

Maybe this balanced cold just supplies the shower?, shut the isol valve again and select the shower to fully cold and then fully hot and see what happens.
There is, what looks like a ABV, automatic bypass valve just to the left of that isol valve handle, this should have nothing to do with the hot or cold water and is probably on the primary boiler HW, just identify it.

 

[rado16v]

Turned off that isolator and let the showers run, hot and cold and didn't see any difference. The hot runs hot and cold runs cold, no difference in pressure or flow

 

[Johntheo5]

So, the balanced cold doesn't seem to supply either the shower or the taps but the supply to them is taken off after the softener, I can only suggest you try and find this take off and also trace the balanced cold back to see what its serving, if anything. Or else the balanced cold isolating valve isn't isolating.