THE FLOW OF WATER IN CONCRETE PIPE. 11 
The board of consulting engineers 1 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 design. 2 
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 
iThis 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. 
3 Engin. News, June 6, 1907, vol. 57, p. 612. 
