THE FLOW OF WATEE 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 pipe 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. 



