Water supply and pressure questions

[CPdiyer]

Hello,
I am well into a project to renovate a bathroom,
Question 1; I am wanting to install a water supply to the property to replace the lead pipe, a contractor tells me that the supply would not have to exit inside the property but could actually exit inside the attached garage - true or a tall tale?

Question 2; the hot water supply pipe from the combi boiler is 15mm some point through the house it is stepped to 22mm - I know the pressure is the same but surely this would slow the flow rate?

Thanks

 

[Newboy]

1. True

2. Static pressure would be the same. Dynamic pressure may be lower as may flow rate. Both dependant on pressure and flowrate from service pipe.

 

[CPdiyer]

Back again, water supply is taken care of with plastic 25mm, but have a further question regarding flow.
Would it be better to run a 22mm pipe off the mains as a sort of feed for the all the taps/outlets and then just before the outlets drop down to a more conventional 15mm for ease?

Or would doing this be pointless and be the same as running 15mm from the plastic mains inlet.?

Trying to ensure maximum flow rate at all points going forward, as already gone to great effort.

 

[Tipper]

Yes.

The smaller the pipe, the more the pressure drop. More pressure drop = less flow. See Bernoulli's Theorem.
If you use smaller pipe size throughout then flow will drop due to the above when more than one tap is opened. Use larger pipe for all main distribution pipe runs.