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 
winding 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ping length is dipped in a bath of hot asphalt and when withdrawn is 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 w r ood 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 
