Prevention Tips: To limit the magnitude and frequency of pressure surges
Definition: Few piping systems are operated under “static” conditions for long periods of time. Hydraulic transient conditions or “surges” occur in every irrigation system. A pressure surge or “water hammer” is created any time the flowrate changes in a piping system. This may be caused by valve operation, pumps starting or stopping, linebreaks or rapid escape of entrapped air.
Prevention Tips: To limit the magnitude and frequency of pressure surges, system operators should use the following guidelines:
Operate the system to maintain pump flowrate as uniformly as possible. This will not only reduce hydraulic transient problems but will increase the life of the pumping unit.
Attempt to balance system flows so the sprinkler set changes are systematic within system subunits. Avoid changing from one main area of the system and back again in the operating program. Maintain sub-unit flows uniformly, if possible.
Run fewer sets for longer times. Hydraulically, it is easier on the system to run a given set as long as possible, provided runoff does not occur, or the moisture holding capacity of the soil is not exceeded. This will allow for fewer sets and, thereby, fewer opportunities for surges to occur.
Avoid operating too many sprinklers in one area of the system and elevating the operating velocities. Use the design guidelines to govern the number of sprinklers that may operate simultaneously on a given pipe segment or loop.
Source: “Designing, Operating and Maintaining Piping Systems Using PVC Fittings” Ron Bliesner, February 3, 1987