10mm feeds to sinks

[wannocks]

Hi Chaps, I mostly work on gas but have a plumbing question. I have an unvented cylinder in my loft feeding the bathroom below it and the kitchen below that. I have a 22mm supply up to the cylinder and back down to the bath. This is then split to 15mm feeds to the kitchen sink and bathroom basin.
It takes some time (and a lot of water!) before any hot appears at the kitchen sink, not so bad at the basin. I'm toying with the idea of running a 10mm pipe to the kitchen sink from the loft to reduce the volume of water before hot appears. Pressure is good, around 3bar running and fills the sink quickly. Are there any pooh traps to be avoided? Bad idea?
Any advice would be appreciated.

 

[compheat]

Its all down to flow rates, so I cant see a problem other than it'l take longer to fill sink,

You could put a pumped return on cylinder that way its instant hot water.

 

[wannocks]

Thought as much, would probably work out the same as ditching 2 sinkfulls of cold water before the hot arrives. Didn't want to go for secondary circ. Bronze pumps are bloody expensive!
Existing runs are in Hep so just need to decide whether to split in loft or under bath. All the pipes are in one box that runs from loft to kitchen. The kitchen and bathroom are to be replaced as funds allow!

 

[mysteryman]

Go for it - it makes good sense. It is how they do it elsewhere.

 

[ChrisR]

"ordinary" mains through several washing machine hoses still gives enough flow for a sink. Have used about 10m of them for flushing through rads. They'd barely be 10mm bore