THE FLOW OF WATER IX DEAIX TILE. 
13 
INTERNAL SIZE OF DRAIN TILES. 
It is generally known that drain tile are not exactly of tlie dimen- 
sions corresponding to the nominal size. All of the concrete tile used 
in these experiments were under the nominal size, while the clay tile 
generally were larger than the nominal size. However, the concrete 
tile more nearly averaged the nominal size than did the clay tile. 
Although in actual practice the nominal or commercial size of tile 
is invariably used in computing the discharge, yet to determine 
acciu-ately the retardation factors it is essential to know the correct 
average diameter of the drain tile being tested. To determine the 
average diameter of all the tile tested at the experimental plant, two 
measurements were m.ade at right angles to each other at each end of 
every tile. This task required the recording and averaging of 1,160 
measurements when tile in 2-foot lengths were used, and twice this 
number when tile in 1-foot lengths were used. 
Table 1 gives the dimensions and cross-sectional areas of each 
kind of tile tested at the experimental plant. From a study of this 
table several points are revealed. In the first place, considerable 
error would have been introduced into the final results had the 
nominal or commercial diameter — instead of the actual, measured, 
average diameter — been used in the computations. For example, 
the mean velocity for the 6-inch clay tile at a grade of 0.50 foot in 100 
feet, with a depth of flow of 0.498 foot and discharging 0.554 second- 
foot, is, when computed from the measured average diameter, 2.659 
feet per second; with the nominal or commercial diameter the 
velocity is 2.823 feet per second. As a rule the mean of the areas of 
the tile computed from the diameters varying most above and 
below the measmed average diameter, with their companion diame- 
ters, varies little from the area computed from the measured aver- 
age diameter. 
Table 1. — Comparison of dimensions and areas of various Jcinds of tile used^ 
1 
2 3 
^ 1 5 
6 
7 
s 
9 ^ 10 ^ 11 
12 i 13 
i Com- 
Ac- 
^-ari- 
ation 
Diam-L^p^ii 
eter i:^^!! 
Diam- 
eter 
Areai 
Kind 01 tile. 
Com- 
mer- 
cial 
size 
mer- 
cial 
or 
nom- 
tual 
meas- 
ured 
aver- 
Area 
com- 
puted 
Area 
com- 
puted 
in 
area 
be- 
tween 
Small- 
est 
meas- 
ured 
nor- 
mal 
to 
diam- 
diam- 
eters 
in 
cols. 
8 
and 
9. 
Larg- 
est 
meas- 
ured 
nor- 
mal 
to 
diam- 
diam- 
eters 
in 
cols. 
11 
and 
12. 
of 
tUe. 
inal 
diam- 
age 
diam- 
eol. 3.|coL 4. 
cols. 
5 
diam- 
eter. 
eter 
in 
diam- 
eter. 
eter 
in 
eter. 
eter. 
and 
6. 
col. 
8. 
col. 
11. 
In. ! Feet: 
Feet. 
Sq.ft. 
Sq.ft. 
P.ct. 
Feet. 1 Feet. 
So.ft. 
Feet. 
Feet. 
Sq.ft. 
4 n. sa-^.-^in. 32sn!n. osts 
0.0S45 
.0907 
.1338 
.1381 
.1940 
.2111 
.3406 
.3685 
.5377 
.54n9 
,7721 
-1-3.2 
-3.9 
-fl.2 
— 7.4 
-f2.4 
-5.5 
-M.4 
-0.6 
+ 1.7 
0. 3100 0. 3300 
0.0804 0.3.380 
0. 3:320 0. 0881 
Hard-burned clay 
4 
5 
5 
6 
6 
S 
8 
10 
10 
. 3333 
.4167 
.4167 
.5000 
.5000 
.6667 
.6667 
.8333 
. R3a3 
.3398 
.4127 
.4193 
.4970 
.51S4 
.6585 
.6850 
.8274 
.8360 
.9915 
.0873 
. 1364 
. 1364 
.1964 
.1964 
. 3491 
.3491 
.5454 
.5454 
.7851 
.3150 
.3950 
.3780 
.4850 
.4760 
.6400 
.6700 
.8080 
.7950 
.9630 
. 33S0 
.4100 
.4510 
. 4850 
,5260 
.6450 
.6720 
.8110 
.8300 
.97S0 
.0837 
.1272 
. 1349 
.1847 
.1971 
.3242 
, 3536 
.5147 
,5185 
.7398 
.3520 
.4220 
.4350 
.5130 
. 5350 
.6770 
. 7360 
.8420 
.8650 
1.0100 
.3500 
.4180 
.4:^0 
.4950 
.5300 
.6620 
. 7030 
.8410 
.8400 
1.0000 
.0968 
Concrete 
.1385 
Hard-burned clay 
,1473 
Concrete 
.1905 
Soft-burned clay . . 
,2227 
Concrete 
. 3520 
Hard-burned clay 
.4066 
Concrete 
.5562 
Vitrified 2 
,5708 
Concrete 
121.0000 
. 7933 
Vitrified 2 
121.0000 
.9857 
.7854 
.7631 
+ 2.8 
.9700 
.9760 
.7436 
1. 0200 
.9980 
.7996 
Computed as an ellipse. 
These tile were in 2-foot lengths; all others in 1-foot lengths. 
