4 BULLETIN 906, U. S. DEPARTMENT OF AGRICULTURE. 



of the failures arising from the use of this kind of piping in the 

 West have been due 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 AVestern 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. Recently 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 

 $2.25 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. 



