No hot water to one tap only

[Jillbills]

We have a Worcester Bosch R35HEPlus combi boiler. We have been experiencing for quite some time now no hot water from the tap in our downstairs cloakroom sink. We recently changed the sink for a larger one and replaced the tap for another but this did not cure the problem.
Several months ago we could not get hot water anywhere in the house and ordered a new 3 way diverter valve but ended up returning it as the hot water mysteriously came through again. The problem still remains with the one tap in the cloakroom only. I have researched this on-line looking for people with similar trouble and have seen suggestions that it could be a stretched or split diaphragm causing it.
I have consulted the installation and servicing instructions that came with our boiler but the only diaphragm mentioned is in the mixer unit assembly. I am unsure as to whether this is the same type of diaphragm, or can you only replace the diverter valve on this particular boiler? Would replacing the diverter valve be the answer to this problem?

 

[MrGassafe2011]

Since the New CHB Install have you EVER got hot water from this tap ?

Does anywater flow from it ?

 

[Jillbills]

Thanks for your swift reply. Yes, the cloakroom was part of a garage conversion after the boiler was installed and the hot water was working at the start. It is a mono-block tap and we get a low water flow when turned to hot, it appears that the flow is not enough to ignite the boiler. If we turn on another hot tap in the house then it will come through. It also seems to work when the central heating is on. We have tested the flexi-hose from the copper pipe to the tap and there are no kinks or twists.

 

[MrGassafe2011]

When the taps were replaced was water flow checked ? Could be a potential blockage in pipework !

 

[Jillbills]

I am not sure if the water flow was checked, all I can say is the hot flow is about half as strong as the cold flow from the same tap. We wondered if the pipe-work could have a partial blockage. This we assume can be a big job to correct as it entails taking up the floor and replacing all the copper pipe going back to the boiler. Fortunately it is the closest tap to the boiler.

 

[MrGassafe2011]

Worst case scenario yep - Or tee into another DHW Pipe ane pipe to the tap ( Providing the Flow is good of course )

Sorry i cannot help anymore

 

[Jillbills]

Thank you very much for your help.