Pipe size example
How much water through a 32 mm pipe?
A 32 mm pipe can move much more water at the same velocity because the cross-section is larger.
Quick estimate
Using a typical 1.5 m/s velocity
Example build-up
Internal diameter: 32 mm. Velocity: 1.5 m/s.
Estimated flow is about 72.4 L/min, or 4.34 m3/h.