


SPRAY IRRIGATION. 25 
It is easy to lay, but its ccmparative shortness of life is its chief 
disadvantage. 
CAST-IRON PIPE. 
Cast-iron pipe, such as is commonly used in city water systems, is 
adaptable for the larger installations of spray systems. Standard 
cast-iron pipe, 4 inches and larger in diameter, is made in 12-foot 
lengths. It is also made in two weights for 100 and 200-foot pressure 
heads. Usually the lighter weight is sufficient for spray irrigation 
systems, especially after the field is reached. Joints are made by 
pouring hot lead into the bell end of each section, or a bolted joint 
may be used. In some instances a rich mixture of cement mortar may 
be driven into the joint instead of lead. Connections for the laterals or 
nozzle lines are made with special fittings, or the shell of the pipe 
may be tapped and a saddle of metal or concrete placed around the 
connection. 
The advantages of cast-iron pipe are its long life, comparative 
cheapness in the larger sizes where freight hauls are short, and ease 
of laying. The disadvantages are tendency to rust and scale after 
lying idle, heavy weight for long freight hauls, and need of special 
equipment for laying and tapping. 
WOOD-STAVE PIPE. 
Wood-stave pipe made of durable fir or redwood is used extensively 
for pressure conduits in the Western States. The pipe is built of 
carefully machined staves, which are held in place by metal bands. 
This pipe can be secured in sizes 2 inches in diameter and larger. 
The smaller sizes usually are made in sections and joined together by 
means of a-collar or sleeve. Large sizes may be built continuously in 
the field. Connections for laterals are made easily by metal saddles. 
The metal bands should be heavily galvanized and the wood treated 
with a preservative. The advantages of wood pipe are its compara-. 
tive cheapness in first cost and smoothness of bore. Provision should 
be made to keep the pipe full of water, otherwise the staves will dry 
and decay. 
TYPES OF PUMPS FOR SPRAY IRRIGATION. 
| All spray irrigation plants require power pumping equipment un- 
| less pressure can be supplied from an elevated source or municipal 
water works. To generate a spray requires a high-pressure pump 
producing 25 to 40 pounds pressure on the nozzles in addition to ele- 
vating the water to the field. The two types of pumps used for this 
purpose may be classified under “ displacement” and “ centrifugal ” 
pumps. 


