10mm pipe length

[Pete]

Been quite a bit of discussion about plumbing layouts and using manifolds recently and on the back of this I need to run four 10mm pipes to two bathrooms to feed the toilet and basins. The distances involved are approx 15m and 21m to each bathroom , one bathroom will be used by our son when home from uni and then hopefully he will be moving out? and the other will be for guests. I am not overly bothered about the toilet pipes but is the distance for the 10mm pipes to the basins overly long or will people just have to be patient? TIA 

[Triassic]

I'm also looking at using 10mm to the sinks (hot and cold) in the bathrooms and 10mm to all toilets. I've used 10mm to toilets in the past and the fill rate has been fine.

[scottishjohn]

as long as your mains pressure is good 

[Oz07]

Not to hijack but i'm planning to use 10mm in a renovation scenario. It's a gravity fed system. It will be swapped over at some point to mains pressure. Is 10mm asking for trouble or will it be fine while on gravity? I assume if it works for 1/2" copper it should work fine for 10mm

[PeterW]

Pressure has nothing to do with it. Flow of 3.5l/m in a 10mm pipe will give you around 16 seconds to get hot at 21m. The same run done in 15mm would be nearer 42 seconds.