

SPRAY IRRIGATION. 35 
general estimating purposes. Small plants under 100 gallons per 
minute, especially in the case of centrifugal pumps, are apt to re- 
quire a greater horsepower than given, while the larger plants should 
require somewhat less, due to the greater efficiencies. In every case, 
however, the actual OTERO to use should be determined by the 
manufacturers furnishing the pump. | 
OUTLINE OF PROCEDURE FOR INSTALLING SPRAY IRRIGATION 
SYSTEMS. 
This outline is for the installation of an overhead spray plant, but 
by substituting underground laterals and nozzle risers for nozzle 
lines and posts it will apply to the stationary, circular nozzle type of 
system. 
First, excavate a trench for the main feed pipe. Second, lay the 
main feed pipe. Third, screw nozzle line risers into main feed pipe. 
_ Fourth, install posts for nozzle lines. Fifth, assemble and tap nozzle 
lines for nozzles. Sixth, install pumping equipment and_ house. 
Seventh, pump water thorugh distribution system to flush out dirt. 
Eighth, install nozzles in nozzle lines. 
INSTALLING THE MAIN FEED PIPE. 
The main feed pipes are expensive items and therefore should be 
carefully designed and located. Usually the main pipes should be 
made as short as possible and yet intersect the nozzle lines at inter- 
vals so that their length will not exceed 600 feet; otherwise the sizes 
of the nozzle lines become large enough to offset any saving in cost 
from the use of fewer mains. The field to be irrigated should be 
divided into irrigation units, each unit having an area to correspond 
to the capacity of the main and pumping plant. The main feed pipe 
|. should be given sufficient size to carry the water for one unit at a time 

without excessive friction loss. (See Table 2, p. 30.) When the most 
distant unit is reached the main can be decreased in size gradually to 
correspond to the amount of water taken out by each nozzle line, 
unless the full capacity is needed for extension or another type of 
_ irrigation in an adjoining field. All pipe over 2 inches in diameter 




should be cut in the shop to fit the spacing of nozzle lines. Straight 
mains of the larger sizes should be equipped with expansion joints 
near the pumps to absorb the contraction and expansion of the pipe 
due to changes of temperature. Easy bends should be used where it | 
is necessary to change the course of the main. All angles retard the 
flow of water by friction. 
The main feed pipe should be laid underground below the depth of 
cultivation and on a grade so it can be drained at convenient places, 
especially in regions where freezing occurs. The main should be 




