2 BULLETIN 852, TJ. S. DEPARTMENT OF AGRICULTURE. 
are the only items requiring an extended haul. Its cost, compared 
with that of cast iron and steel, its permanence and comparatively 
fireproof qualities, are in its favor. When reinforced it is usually 
more costly than wood-stave pipe, and has not the required elas- 
ticity of wood or metal when subjected to a wide range of tempera- 
tures or to water hammer. Proper expansion joints will care for 
temperature changes. 
Concrete pipe has usually been considered inferior to wood pipe 
in carrying capacity and the tests described in this paper confirm 
this belief as regards average wood pipes and average concrete pipes. 
These tests also show that the highest grade concrete pipe will convey 
slightly more water than can safely be assumed for the same size of 
wood-stave pipe. The results of a study of the capacity of wood-stave 
pipes were embodied in a previous paper. 1 
While most of the experiments described in this bulletin were 
made on pipes under pressure, there are some tests on record which 
were made on flow-line pipes and conduits running to partial 
capacity ; that is, with the surface exposed to the air The experiments 
made under these two conditions will be taken up separately, in parts 
1 and 2 of this paper. 
NOMENCLATURE. 
Unless otherwise noted, the various symbols used throughout this 
publication will have the following significance: 
d — The mean inside diameter of the pipe in inches. 
D — The mean inside diameter of the pipe in feet. 
r — The mean inside radius of the pipe, or JD, in feet. 
Q — The mean discharge of the pipe, during the test, in second-feet. 
A — The mean area of the pipe bore, in square feet, =?rr 2 . 
V — The mean velocity of the water, during the test, in feet per second. 
L — The length of reach tested, in feet. 
hf — The head of elevation lost in overcoming internal resistance within a fairly straight 
TTT 
pipe of uniform size, in feet, = . 
H— The above loss (termed friction loss) per 1,000 linear feet of pipe = -i-= — A 
Li 
h v — The head of elevation lost in creating the mean velocity, V, in feet. Called 
velocity head. 
hf v — The velocity head recovered as the velocity is reduced at the pipe outlet, in feet. 
h e — The head of elevation lost at a pipe intake due to impact and entrance resistances, 
in feet, here called entry head. 
P — The wetted perimeter; in a pipe underpressure, the inside circumference, =tD 
or 2irr, in feet. 
R — The hydraulic radius =^; in a circular pipe, underpressure, =— . 
s — The hydraulic grade or slope, in feet per foot of length of a pipe of uniform size, — • 
Li 
C — The coefficient of retardation in Chezy's formula. 
n — The coefficient of retardation in Kutter's formula. 
n 1 — The coefficient of retardation in Manning's formula, 
m — The coefficient of retardation in Bazin's (1897) formula. 
1 "The Flow of Water in Wood-stave Pipe," by Fred C. Scobey, Bulletin 376, U. S. Department of 
Agriculture, 
