4 BULLETIN 906, TJ. S. DEPARTMENT OE AGRICULTURE. 
of the failures arising from the use of this kind of piping in the 
West have been clue to the practice of laying discarded sewer pipe as" 
distributaries in irrigation systems. Some of these are imperfectly 
burned and glazed, possess little strength and are apt to disintegrate. 
Others are cracked, permitting roots to enter the pipe and obstruct 
the passageway as well as break up the pipe. The cost of a good 
quality of clay pipe is higher than a corresponding quality of plain 
concrete pipe. The latter will also safely withstand higher internal 
pressures. For these and other reasons clay pipe has not been ex- 
tensively used for irrigation purposes throughout the Western States. 
INCASING OLD PIPE OF METAL AND WOOD WITH CONCRETE. 
Old pipe of metal and wood may be converted into concrete pipe 
by placing a layer of concrete around their exteriors. This can often 
be done with the pipe in place, under pressure and in use, providing 
the leaks are not too troublesome. 
In the case of steel pipe, the pipe is uncovered and scraped clean 
of dirt and rust with steel brushes. The excavation is made large 
enough to permit forms to be placed around the sides and part of the 
bottom of the pipe. Before placing the forms triangular mesh rein- 
forcing wire of the right width is wound spirally around the pipe 
and is kept away from the pipe by small concrete briquettes. 
Wooden forms 12 feet in length are then put in place, allowing suffi- 
cient space between the forms and the exterior of the pipe for the 
proper thickness of concrete shell. Concrete is then poured within 
the form, which is allowed to remain in place 24 hours before remov- 
ing. Eecently the Sweetwater Water Co. of San Diego County. 
Calif., incased 3,125 feet of 8-inch steel-riveted pipe for a total 
cost of $1.13 per foot, which included trenching, backfilling, forms, 
etc. The same company also encased 600 feet of 12-inch pipe 
for $1.39 per foot. Several years ago the Temescal Water Co., of 
Corona, Calif., incased with concrete 10,000 feet of riveted steel 
pipe, under a maximum head of 80 feet, which had been in service 
for 30 years, 1 also shorter lengths of pipes 30 and 18 inches in di- 
ameter. The cost inclusive of trenching, forms, backfilling, etc.. was 
§2.50 per foot for the 30-inch pipe, $1.70 for the 24-inch, and $1.40 
per foot for the 18-inch pipe. The price of labor at that time was 
S2.25 to $2.50 per day. while cement was worth $2.30 per barrel. 
The form used is shown in figure 1. 
CONCRETE PIPE. 
During the past 10 or 15 years the greater part of the pipe used 
for irrigation pipe systems has been made of concrete. The prin- 
1 See article in Engineering News-Record by H. R. Case, Sept. 20, 1917. 
