Table 1 shows the maximum flow rate for various size pipelines when the water velocity is 5 feet per second. Maximum flow rate based on pipe diameter. The velocity and the roughness of the pipe determine the amount of head loss due to friction in a pipeline. Head loss or pressure loss due to pipe friction translates directly to energy loss. The more head loss, the more you pay for pumping energy.
Smooth pipe has less friction than rough pipe.
Plastic pipe, such as PVC and polyethylene, is the smoothest followed by aluminum, steel and concrete, in that order. Table 2 shows the friction head loss of aluminum and PVC pipe for several pipe diameters. The head loss is given in feet per 100 feet of pipeline. Flow rates below the horizontal line for each pipe size exceeds the recommended 5-feet per second velocity. As an example of how to use this formula, lets say you pump 1000 gallons per minute through a 1500 foot pipeline to a center pivot for about 800 hours per year.