Have a look at the drawing below describing a sample situation:
- a water tank
- a 1'' diameter pipe bringing the water down, inside the ground, arriving near the house
- in the house, 2 x 0.5'' diameter pipes distribute the water from a connection T to various faucets
I'd like to understand the differences between two possibilities: connecting the incoming pipe to the distribution T using a 1'' diameter pipe (possibility 1) and connecting the distribution the T using a 0.5'' diameter pipe (possibility 2). (As you see on the drawing, the water has to go against gravity about 2m to reach the T.)
My "gut feelings" tell me that the first solution is better to maintain pressure if faucets are used on both ends of the T at the same time whereas the second one is better to fight gravity.