posted by Sudesh CANDEN .
Hi Just want to know if water from a 20mm Polyethylene pipe under pressure of 3 bars passes to a 25mm polyethylene will cause a slight increase in volume output with a little drop in pressure? If yes then to obtain this benefit , up to whay size can we go for the second pipe size ? Does this depend on the compression of the water? How much can water be compressed inside a pipe under 3 bars..... thank you for an answer.
I think you are missing something. If this is a flow problem ("passes to"), then what you need to worry about is the change in velocity in the second pipe. Water does not expand, the volume flow rate changes with pipe size and pressure.
Have your seen Bernoulli's equation in your text? I invite you to inspect it.