Odd problem with a combi system

[Timmyturtle]

I went to look at a job last week.
When i got there i found it had a Baxi combi boiler that didnt look that modern,which had (an optional extra) like a small expansion vessel on the water circuit like you have with an unvented cylinder.

The problem the client is getting is.

The downstairs cloakroom (about 3m from boiler) water from the COLD tap flows very slowly as does the toilet filling.The hot is fine

The weird thing is ,that if you open the kitchen tap(adjacent) or the cloakroom hot tap,the water then flows fully from the cold tap and the toilet fills quickly!

Anyone have any idea of what causes this,Ive never had this before

Cold to rest of house is fine .Thanks

 

[ctp]

its an exspansion vessel usually 10ltrs for hot water .re water check there isnt a pev valve across hot and cold.

 

[BOB D.O.L.E]

i think the tap is the problem.