THE FLOW OF WATER IN CONCRETE PIPE. 



OPINIONS OF ENGINEERS REGARDING THE CARRYING CAPACITY OF 



CONCRETE PIPE. 



Experiments upon the flow of water in concrete pipes have been 

 so few in number that there has been developed no clearly defined 

 trend in thought, as was the case with the capacity of wood-stave pipes. 



In his discussion of tunnels, Finkle 1 advocates applying a one- 

 fourth inch coat of cement and sand in a 1 to 2 mixture to give a 

 smooth surface and prevent percolation through the main concrete 

 walls. "By means of this construction," he adds, "the coefficient 

 of roughness in the Kutter formula has been reduced as low as 0.010 

 and in other cases it has been as high as 0.012. If the work is very 

 poorly done it might run to 0.013." 



Schuyler states 2 that the conduit supplying Mexico City was 

 designed with a value of n equal to 0.017, but upon examination after 

 construction he remarks, "The interior of the conduit is very smooth, 

 and answers to Kutter's rating of 0.011." 



In his conclusions concerning the use of small cement-lined iron 

 pipe, Metcalf has this to say of the carrying capacity: 3 



Satisfactory "data are lacking upon the carrying capacity of cement-lined pipes. It 

 is believed that under favorable conditions the coefficient of discharge to be used in 

 the Hazen and Williams formula is about C w =120, but under actual conditions this 

 coefficient has been found, in several carefully observed cases, to lie between 95 and 

 110. Unless the conditions are definitely known, therefore, the use of a coefficient 

 not exceeding C w =lQ0 'to C w =110 in the Hazen and Williams formula is to be 

 recommended. 



Jorgensen used a value of n of 0.012 in the design of a 6-foot rein- 

 forced concrete flow line. 4 



Conway 5 says that n was taken as 0.013 in the design of some 

 lines in Mexico. The pipe units were 61 cm. (practically 2 feet) long, 

 made with a "dry mix" and afterwards coated "with a Portland 

 cement grout to which a little freshly slaked lime was added." 



Table 1. — Friction factors used in designing concrete pipes of United States Reclamation 



Service. 



Project. 



Line. 



Type. 



Size. 



Kutter's 

 used. 



Length. 



Salt River 





Continuous 



do 



Inches. 

 63 

 63 



6 to 30 

 54 

 30J 

 12 to 47" 

 70 

 64 



m 



30* 

 36 



0.012 

 0.012 

 0.013 



Feet. 

 2,130 



Do 





500 



Tieton 







255, 689 







do 



3,100 



Do 







0.013 



3,088 







....do 



61, 728 



Belle Fourche 



Belle Fourche 



Continuous 



do 



0.012 

 0.014 

 "0. 013 

 0.013 

 0.013 



3,565 



Milk River 





1,479 



B oise 







4,770 



Do 





do 



3,546 



Do 





do 



8,575 











1 The Most Economic Type of Hydraulic Power Conduits. F. C Finkle, Eng. Rec, vol. 52, Sept. 2, 

 1905, p. 263. 



2 The New Water- Works and Reinforced Concrete Conduit for Mexico City. J. D. Schuyler, Eng. News. 

 vol. 55, Apr. 19, 1906, p. 435. 



' Wrought-Iron Cement Lined Water Pipe. Leonard Metcalf, Eng. News, vol. 61, p. 2, Jan. 7, 1909. 

 4 Eng. News, vol. 62, Aug. 5, 1909, p. 146. 



6 The Water Works and Sewerage of Monterev, Mexico, by G. R. G. Conway: Trans. Amer. Soc. Civil 

 Engin., vol. 72, 1911, p. 497. 



