Water supply to outbuilding - Pipe size?

[mwerner]

Hi
I'm going to be running a blue mdpe water pipe to the outbuilding in my garden and am wondering about pipe sizes. It's only going to be used for a small hand basin and an outside tap.
Its a distance of approx 18m and recommendation seems to be to use 25mm blue mdpe pipe. However, I'm going to be connecting the supply into 15mm copper pipe under our kitchen sink in the main house so is there any point in going for 25mm pipe or will 20mm do? Am I still likely to get better flow rate in the outbuilding if I use 25mm pipe, despite being limited by the 15mm copper pipe at the supply point? Also, is 25mm pipe likely to give better frost protection over 20mm pipe?

Regards
Martyn

 

[Wayners]

I remember watching this..

One of the guys I follow..
Yeah better flow rate.
Some in our road have 25mm pipe fitted to replace 15mm copper in ground. Massive difference in the house dispite 15mm