The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Sprinkler Irrigation
systems arc classified as permanent or portable according to the type of installation. The permanent installations have permanent mains and laterals whose size is graduated down from the main to the last sprinkler. They may have either permanent sprinklers installed at each sprinkler location and control valves on each lateral at the main ; or they may have quick coupling valves at each sprinkler location with sprinkler attached to valve keys for one complete set. In the latter variety the keys and sprinklers are moved after each operation.
The portable installations may have permanent mains and portable lateral lines, portable mains and portable laterals with permanent water source, or portable mains, laterals and pumping units where the source of water is an open ditch or low pressure- pipe.
No matter what the system, its design must be based upon the water and pressure that is available.
There arc sprinklers that will operate efficiently on pressures from 5 pounds to 120 pounds. When using the term "pressure" in discussing a sprinkler system it must be remembered that the term refers to available operating pressure at the sprinkler nozzle. With any given nozzle size or combination of nozzle sizes, the quantity of water delivered, called discharge, will increase with the pressure. The diameter of the coverage also increases. With a constant pressure an increase of nozzle size will increase both the discharge and the diameter of coverage. It follows, then, that the lower the available pressure and the smaller the nozzle, the closer together the sprinklers must be set, and the more operations will be required to cover a given area. Each system, whether permanent or portable, must be designed according to the available water and pressure. The amount of water available cannot be changed, of course, but available pressure may be increased either by installing a new pumping plant or a small booster pump.
It has been proven by numerous tests that the maximum spacing of sprinklers for efficient operation is 65 percent of the diameter of coverage. This applies for wind conditions up to 4:0 miles per hour. Where sprinklers are to operate in higher winds special planning is required.
Low pressure systems arc used to take advantage of available pressure in low pressure pipes. However, each setting or lateral line covers only a small area which requires short moves and consequent higher labor costs. A high pressure system covers a larger area, allowing .1 greater distance per move thus lowering the cost of labor for a given area.
