100 BULLETIN 852, U. S. DEPARTMENT OF AGRICULTURE. 
very careful work, but demonstrating to my mind that it was possible 
to build a cement pipe that roots would not enter. This was a 
jointed cement pipe built by Mr. Stowell, of Los Angeles. The 
examination was being made for purposes of reorganization. 
DISCUSSION BY MR. NEWELL. 
With respect to the liability of concrete pipe to show decreased 
carrying capacity with age, my experience may be of some value. 
February 26, 1918, I inspected the interior of three concrete pipe 
lines, the R 1? D 1} and M pipes. 
R x pipe (No. 32 and 88a). — Interior diameter 46 inches; thickness 
of shell 3 inches; laid in winter of 1909-10; in use 8 years. The 
interior for several hundred feet from the intake appeared as good 
as when first laid. The impressions of rivet heads in the steel forms 
were clearly visible in the concrete. For the first few pipe lengths 
from the intake there had been a very slight abrasion on the bottom 
of the pipe. It is over this stretch that the water flows freely when 
first entering the pipe and down which some gravel rolls. 
D t pipe (No. 23 and 24a). — Interior diameter 30 inches; thickness 
of shell 3 inches; laid in February-March, 1910; in use 8 years. On 
account of the relatively small diameter of this pipe, the inspection 
did not cover any great distance from the intake end. A little 
abrasion near the bottom of the pipe was observed for the first few 
feet; thereafter the pipe appeared as good as new, slight irregularities 
in the forms being clearly indicated on the concrete. 
M pipe. — Interior diameter 47 inches; thickness of shell 2}^ 
inches; laid in winter of 1907-8; in use i0 years. On account of 
some seepage flow into the pipe, inspection had to be made at the 
outlet end. As in the other two cases, the interior seemed to be in 
as good a condition as when the pipe was first laid. 
Considering the length of service of the three pipe lines, the fact 
that they are in use about 7 months each year and dry 5 months, I 
know of no other type of construction which seems to promise such 
length of service, coupled with little or no decrease in carrying 
capacity. 
Some have felt doubt as to the permanence of the concrete pressure 
pipes with thin shells on account of the possible destruction of the 
steel due to the slow j^assage of water through the shell. A few days 
ago we had occasion to cut into the D x pipe for the purpose of insert- 
ing a valve, and found the steel as bright as when first laid. I am 
sending you a small section herewith. 1 The sample of steel was 
taken where the pipe is subjected to a head of slightly more than 40 
feet. Samples taken from other pipe lines have uniformly given the 
same result, indicating that there is little likelihood of deterioration 
in steel in this type of pipe. I may add that in no case has our 
reinforced-concrete pipe,. built by the wet process, shown any material 
defects of construction or any sign of deterioration. 
1 To all appearances the steel is new. 
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