Pressure drop increases proportionally to the frictional shear forces within the piping network.
A piping network containing a high relative roughness rating as well as many pipe fittings and joints, tube convergence, divergence, turns, surface roughness, and other physical properties will affect the pressure drop.
For example, a larger pump could be required to move a set amount of water through smaller-diameter pipes (with higher velocity and thus higher pressure drop) as compared to a system with larger-diameter pipes (with lower velocity and thus lower pressure drop).
[6] Pressure drop is related inversely to pipe diameter to the fifth power.
[7] For example, halving a pipe's diameter would increase the pressure drop by a factor of