USE OF CONCRETE PIPE IN IRRIGATION. 
43 
the water in the lateral is divided in proportion to the separate 
acreages to be served. The Covina Water Co. has installed diver- 
sion boxes that are fitted with galvanized sheet-iron gates. The 
gates are all set at the same elevation in the box and water may 
spill over into the orchard pipe lines on every side of the box. The 
gates are usually made with rectangular orifices that have several 
sizes of openings. As the head is the same on each gate, the correct 
proportion of water will be delivered to each unit, independently 
of the head over the 
orifice. 
Pipe can be used 
to advantage for 
constructing diver- 
sion boxes as shown 
in figures 21 and 22. 
Where there is con- 
siderable pressure to 
contend with at the 
point of diversion, 
pipe structures can 
be built up in a sin- 
gle length to the re- 
quired height and 
gates operated from 
the top of the 
stands. Overflow 
stands (fig. 23) can 
be made by building 
spillways and thus 
keeping a constant 
head on the mains 
or laterals. Overflow stands may operate automatically, requiring 
no gates, or gates may be made from ordinary orchard valves that 
can be manipulated from the outside of the stand. 
Where pressure is excessive or there is an objection to high stands, 
diversion boxes are sometimes built that extend only a few feet 
above the ground surface, and a top is provided over the stand that 
will withstand the pressure as shown in figure 24. Alfalfa valves are 
commonly used to close the top of the stand. Lateral gates may 
either be of the common, sliding type, or may be orchard valves that 
are loosened by turning on a threaded bolt. 
A diversion box has been designed that will relieve high pres- 
sures without the use of high relief or overflow stands. This box 
makes use of an automatically controlled valve that will open the 
gate in the main when pressures tend to become high at the point of 
Fig. 22.- 
A diversion box formed wholly of concrete pipe 
having small air vents. 
