2.2 Friction

The process of flow and pressure would be easy to deal with, if pressure was not lost to friction in pipe flow.

Friction loss is an accumulative reduction in pressure which is a function of the surface roughness of inside pipe walls, the diameter of the pipe, the velocity of the water, and the number of path restrictions along the way.

Friction loss tables are available for different pipe materials and sizes to aid in selecting pipe sizes. Friction loss is expressed in psi; for pipe, friction is expressed in psi per 100 feet of length.