THE FLOW OF WATER IE" CONCRETE PIPE. 11 



The board of consulting engineers * who reviewed the plans of the 

 Los Angeles aqueduct suggested a coefficient for cement-lined 

 tunnels of 0.014 for n in the Kutter formula. This value was used 

 in the accepted designs- 

 After conducting a series of experiments upon both open and 

 covered channels in southern California (see p. 88 in Appendix) 

 J. B. Lippincott concluded: 3 



It would appear from these experiments that a coefficient of 0.012 for n in the 

 Kutter formula would be safe in tunnels or covered concrete conduits with plastered 

 surfaces. 



In correspondence with the writer, under date of June 15, 1915, 

 Mr. Lippincott writes : 



An interesting feature relative to coefficients is the fact that in concrete-lined 

 conduits in the Southwest, the effect of sunlight is very material in determining 

 what the coefficient will be in the conduit. In the covered conduits that are dark 

 there is no growth of vegetable or animal life in this section and our values of n are 

 in the neighborhood of 0.010 to 0.012. If, however, the same class of lining is uncov- 

 ered and exposed to the light of the sun, the coefficients are very much more unfavor- 

 able and may run up to 0.018. 



RECAPITULATION. 



As a broad statement, it would appear that the concrete pipes and 

 conduits of the country have been designed by the use of the Kutter 

 formula, and that concrete has been considered as concrete, little or 

 no differentiation being made due to various degrees of smoothness, 

 regardless of forms, mixtures, or surfacing, although the acquired 

 surface, due to slimes, has been considered. 



Values of n have been chosen from 0.012 up to 0.017, the reasons 

 for this wide divergence not being quite clear in several cases. In 

 no case has the designing engineer accepted literally the Kutter 

 classification of 0.010 for "neat cement plaster" or 0.011 for "cement 

 mortar one-third sand." It may be well to state here that these 

 values of n are the only ones given in many standard lists that appear 

 to apply to concrete and were based on very few data obtained under 

 conditions that were probably more nearly ideal than commonly 

 could be obtained commercially. 



The Kutter formula has been particularly popular in the West, 

 while in the Eastern States the Williams-Hazen formula is exten- 

 sively used alongside that of Kutter. 



A study of Tables 3 and 11 and of Plate VI will develop what 

 coefficients may be expected from various methods of construction 

 for varying sizes of pipe and varying velocities. While it is still 

 evident that the Kutter formula should not be used with a given 

 value of n for a given interior surface throughout the range of sizes 



x This board consisted of Jno. R. Freeman, J. D. Schuyler, and F. P. Stearns. 

 2 Construction of the Los Angeles Aqueduct, Los Angeles, Calif., 1916, p. 81. 

 s Engin. News, June 6, 1907^ vol. 57, p. 612. 



