Jadnashua
Retired Defense Industry Engineer xxx
A short section of smaller pipe acts like a venturi, and doesn't significantly affect the overall flow rate, but 30' of a smaller pipe definately will. Once in the house, branching off to smaller, single use connections is fairly normal. It's just that your supply is marginal, in my opinion, if you are looking for high flow without loss of pressure. When you try to get high flow out of a pipe, the higher you go, the more friction. Plus, you don't want the fps to be too high, either. a figure in the range of 5-6 fps is the range you want for the maximum.
On copper tube sized cpvc, the id of a 3/4" pipe is nominally around 0.690", so at 6fps, that comes out to 7 gallons/minute. Now, your supply pressure will affect that flow as will any other restrictions (such as branching off to smaller pipes). While 3/4" copper is about 3/4" id, at the same velocity flows about 8.25gpm, or about 18% more. Bump that up to a 1" pipe and you have 14.7gpm, or 78% more. So, as you can see, changing the ID of the pipe just a little means (at the same pressure and flow rate) you can supply a lot more water. And, because the friction losses are smaller with larger pipe, you'll see closer to that theoretical maximum with less pressure loss.
On copper tube sized cpvc, the id of a 3/4" pipe is nominally around 0.690", so at 6fps, that comes out to 7 gallons/minute. Now, your supply pressure will affect that flow as will any other restrictions (such as branching off to smaller pipes). While 3/4" copper is about 3/4" id, at the same velocity flows about 8.25gpm, or about 18% more. Bump that up to a 1" pipe and you have 14.7gpm, or 78% more. So, as you can see, changing the ID of the pipe just a little means (at the same pressure and flow rate) you can supply a lot more water. And, because the friction losses are smaller with larger pipe, you'll see closer to that theoretical maximum with less pressure loss.