Hope you can help, I fitted. Combi boiler last week, when I done the quote I used a flow cup on the downstairs tap and from what I can remember it was fine.
I have converted the system from a system to combi boiler, the new boiler needs 14.5 litres a minute it's getting about 13, now although it's under it's just under, and having fitted 100 s of combi's I fully appreciate the flow rate problems with comb is but when one tap is open downstairs the other tap downstairs, is maybe at 30% flow rate and the bath tap has absolutely no flow rate.
The main complaint is the bath and the shower that they plan on installing this month won't work properly.
All header tanks have been cut out.
The hot water pipe is completely in 22mm except for about 5 metres which We have reduced to 15mm, would you advise increasing the 15mm in to 22mm or do you think the result will be minimum, the 15 mm is all upstairs, however when I say it's all 22 the downstairs is 15mm.
Do you think the house may be fitted with a pressure reducing valve ( built in 70s) and if so Ny ideas where it may be located?
Any advise will be greatly appreciated, as I don't want the customers to fork out a fortune to the water board.

How exactly did i fit the wrong thing??, They were getting a combi regardless as they ewanted the tank cupboard for a shower and they wanted the header tanks out also. Im not getting the blame just want to give them all the options i can.

Thats just the thing i done the quote about a month before the job and i tested the flow and i thought it was fine otherwise i would have mentioned it i have before.

But regardless of that, the fact is that its maybe 3 litres per min under, so whatever method i use it only has to boost it by a few litres per min.

The combi is a 30kw ideal logic +.