SPRAY IRRIGATION. 25 



It is easy to lay, but its comparative 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. 



