USE OF CONCRETE PIPE IN IRRIGATION. 6 



favorable conditions unless protected by an asphaltic or other similar 

 coating or galvanized. The dipping of sections of riveted pipe in a 

 bath of hot asphalt has long been practiced, but if the coating becomes 

 brittle when cooled, it is liable to chip off and expose the metal. To 

 guard against abrasions in the coating, roofing paper cemented to the 

 pipe with hot tar has been successfully used on several large systems, 

 notably those of the Terra Bella irrigation district in Tulare County 

 and the Sweetwater Water Co. of San Diego County, Calif. In 

 wrapping pipe, a roll of roofing paper is cut in a number of strips by 

 means of a homemade machine. This machine winds a roll of roofing 

 paper from one spindle to another, meanwhile drawing the paper 

 over a series of knives ; the knives can be regulated so as to cut any 

 width of strip desired. The pipe to be wrapped is placed on a 

 spindle which is suspended over a trough. It is then revolved by a 

 crank by one man, while another guides the strip of roofing paper. 

 The paper is thus wound spirally the length of the pipe. A third 

 man pours hot tar between the roofing paper and the pipe while the 

 Avinding process is going on. 



For medium water pressures created by heads of 20 to 100 feet and 

 over, wood pipe may be used. The kind of wood pipe known as con- 

 tinuous stave pipe may be built in sizes ranging from 1 to 15 feet in 

 diameter. The materials of which this pipe is composed consist of 

 wood staves, steel bands, and cast-iron clips, which are shipped to 

 the site usually direct from the manufacturer, and the pipe is laid 

 continuously either in a trench or on the surface of the ground along 

 the line of the location. 



So-called machine-banded wood pipe is made in the factory in 

 shipping lengths and in sizes ranging from 2 to 52 inches. In making 

 this pipe the staves are held together by galvanized steel wire, wound 

 spirally and spaced according to the pressure to be sustained. After 

 the pipe is banded and the ends are milled for couplings, each ship- 

 ping length is dipped in a bath of hot asphalt and when withdrawn is 

 rolled in sawdust or shavings. The light weight and cheapness of 

 wood pipe and the ease with which it can be shipped and transported 

 over mountainous and out-of-the-way places are marketable ad- 

 vantages. The chief objection to the use of wood pipe is the tendency 

 of the wood to decay when in contact with the earth, exposed to the 

 air, and alternately wet and dry. When wood pipe is kept continu- 

 ously under water pressure, or covered to a depth of 2 feet or more in 

 tight soil, it has been known to give excellent service for 30 years. 



Vitrified clay pipe when well made is a suitable pipe for irrigation 

 purposes, providing the head does not exceed 15 feet. It is easy to 

 lay, has a smooth interior surface, and in consequence a fairly low 

 friction factor. It is not as a rule injuriously affected by alkali. Most 



