THE FLOW OF WATER IN CONCRETE PIPE. 65 
Using the classification as listed on page 7 and presupposing the 
use of factors of safety about as given on page 54, the coefficients 
in the Moritz formula are about as follows: 
Class 1. C m =0.90 for velocities up to 3 feet per second. 
Class 2. C TO =1.15 for velocities up to 3 feet per second. 
1.10 for velocities from 3 to 6 feet per second. 
Class 3. C TO =1.25 for velocities less than 2 feet per second. 
1.20 for velocities between 2 and 4 feet per second. 
1.15 for velocities between 4 and 6 feet per second. 
1.10 for velocities between 6 and 8 feet per second. 
Class 4. C TO =1.35 for velocities less than 2 feet per second. 
1.30 for velocities between 2 and 4 feet per second. 
1.20 for velocities between 4 and 6 feet per second. 
CAPACITY OF CONCRETE PIPE COMPARED WITH THAT OF WOOD-STAVE, 
CAST-IRON, AND RIVETED STEEL PIPE. 
Since there are so many classes of concrete pipe, a table showing 
percentage comparisons between the capacity of each class of pipe 
with the capacity of pipes of each of the other materials at various 
ages would be extensive and confusing, so Table 10 may be used. 
This table gives velocities; capacity for a given size pipe is propor- 
tional to velocity. 
In a study of this table, the concrete pipe under consideration 
will classify under columns 3, 4, 5, or 6, according to the class descrip- 
tions given on page 7. Average wood-stave pipe comes under 
column 20. Cast iron and riveted steel come under columns 8, 9, 
or 11, according to age of the pipe. The coefficients in their formula 
recommended by Hazen and Williams for new cast iron, new riveted 
steel, 10-year-old cast iron, 20-year-old cast iron, and 10-year-old 
riveted steel are, respectively, 130, 110, 110, 100, and 100. 
164725°— 20— Bull. 852 5 
