THE FLOW OF WATER IN CONCRETE PIPE. 49 
Class 1. — From a study of the older San Antonio Water Co. and 
Pomona pipes of class 1, a coefficient of 14 was found for K 1} making 
the formulas for this class read : 
H = ^ (18) 
from which 
7= 0.267 H - 5 d™ 25 = 1.26 H - 5 P - 625 = 89 # - 625 & - 5 (18a) 
and 
Q = 0.00146 H - 5 d 2 - 625 = 0.99 H 05 £> 2 - 625 (186) 
Class 2. — Probably more than half the concrete pipes being laid at 
present in the United States are made locally, in 2-foot sections, by 
the u dry-mix ,J hand-tamped, cement-washed process in the west coast 
States. This type of pipe constitutes most of class 2. Throughout 
the irrigated portions of California nearly every town has one "pipe 
For this class of pipes, a study of the newer Pomona and San 
Antonio Water Co. lines, supplemented by an examination of lines 
and pipe units in other parts of California, lead to the derivation of 
10.4 for the coefficient K 2 making the formula for this class read 
„ 10.4 V 2 
H = ^i.25 (19). 
from which 
7-0.310 H 05 d°- 625 = lA7 i? - 5 Z>°- 625 = 103.5 R°-« 25 S - 5 (19a) 
and 
Q = 0.00169 H°* d™ 25 = 1.15 # - 5 P 2 - 625 (196) 
Class 4- — The experiments upon the Victoria Aqueduct, siphon 
No. 1 (pipe No. 30) were chosen as characteristic, because they are 
well supported on the conservative side by those on other exceed- 
ingly smooth finished pipes and the conditions for experimentation 
were so unusually favorable. The coefficient K 4 was found to be 
6.7, making the formula for this class read 
* = 6 -^ (20) 
from which 
7=0.370 H - 5 d°- 625 = 1.75 H - 5 L>°- 625 = 123.5 # - 625 S - 5 (20a) 
and 
Q = 0.00202 i? - 5 d™ 25 =1.37 i? - 5 £> 2 - 625 (206) 
EFFECT OF AGE UPON CARRYING CAPACITY. 
In designing a pipe line of a given material and workmanship the 
engineer must not consider so much the capacity of the pipe when 
new but after a period of subjection to the local conditions that 
finally determine the interior of any pipe line. Deposits of mud, 
gravel, etc., will of course choke any pipe and will not be con- 
sidered in the following discussion, though it may be well to state in 
164725°— 20— Bull. 852 4 
