THE FLOW OF WATER IN CONCRETE PIPE. 93 
of the material and workmanship entering into the structure. 
Thorough inspection is quite as important as careful design and 
well-drawn specifications to avoid the possibility of failure. 
DISCUSSION BY MR. BENT. 
The author has reached a conclusion that in an empirical and 
ignorant way I reached many years ago. Our own struggle in laying 
concrete pipe lines has been, as the result of these conclusions, to 
secure the greatest possible smoothness of joints. I think we began 
to realize the importance of this shortly before we built the 12-mile 
line in Boulder Canyon, which the author has mentioned, and it was 
very interesting to learn that after these years of service he found 
the line carrying the quantity of water for which it was figured. 
At the time we were laying it, the Central Colorado Power Co.'s 
engineers were in a very anxious state of mind because some one had 
accidentally used a lower value for n than the chiefs later on approved, 
but it was then too late to change the diameter of the pipe. It was 
freely predicted that there would be bitter disappointment in the 
amount of water delivered. We tried to have the disappointment 
on the right side and succeeded by care in the work. 
The entire line was laid by us under contract and the joints inside 
and outside were made of 1 : 2 mortar put on solely with a trowel. 
I used to talk about 0.012 being perfectly safe for n and 0.011 as 
being perfectly attainable. I still believe this was right, but it is so 
difficult to control field conditions that for some time we have pushed 
these values up one figure, and that seems to be about the conclusion 
the author has reached. 
DISCUSSION BY MR. FINKLE. 
From experience with the manufacture of concrete nipe and its 
use, the writer has come to the conclusion that the carrying capacity 
of such a pipe is almost entirely in the hands of the engineer having 
charge of its design and construction. This statement relates more 
to the ordinary gravity-flow concrete pipes made in 2-foot sections 
and joined in the trench, but it will also apply in a considerable 
degree to other classes of concrete and cement pipes. 
Three points are important in attaining a high carrying capacity of 
concrete pipes. These may be briefly stated as follows: 
First, use as wet a mixture as possible and thoroughly settle the 
concrete in the forms, making every effort to have gravel and crushed 
rock in the mixture covered by a film of the fine sand and cement mix- 
ture on the inside of the pipe. This object can be attained by using 
more forms, so the sections can remain longer in the forms and a 
wetter mixture can be employed. The increased cost of this will be 
slight, as it will only be the interest on investment and wear and tear 
of the additional forms. 
Second, in laying the pipes the joints must be carefully made so 
that there will be no projections or rough places where the sections 
are united. This can be accomplished by using the revolving brass 
band described in connection with the author's No. 50, experiment 
FF1. 
Third, careful attention must be paid to the alignment and grade 
on which the pipe is laid. This is important, as it eliminates irregu- 
larities in flow due to uneven bottoms and angles or irregularities. 
