THE FLOW or WATER IN DRAIN TILE. 
49 
Equation 13 is tentatively offered for use in computing the capacity 
of tile drains, though with full recognition of the fact that further 
experiments are necessary to determine its applicability to tile of 
sizes larger than those used in these experiments. Additional data 
also are desirable to determine whether the variation in length of the 
individual tiles is an important item to consider in the derivation 
of a formula. 
For convenience in quickly determining the number of acres 
drained, for each size of tile and for various rates of run-off, Plate 
XIII has been prepared from formula 13. Several velocity curves 
are also shown for use in determining approximately the velocity 
of flow. 
LOSS OF HEAD IN CATCH-BASINS. 
To actually determine the loss of head resulting from the installa- 
tion of a surface inlet or catch-basin in a tile line, experiments were 
made on 8-inch clay tile at three different grades, 0.2, 0.75, and 1.50 
feet in 100 feet, with differences of 0.1, 0.2, and 0.3 foot between the 
elevations of the inlet and the outlet tiles. 
The catch-basin was made by inserting in the flume two wooden 
bulkheads 4 feet apart. The space between the bulkheads was 
cleared of tile and earth and thus formed a basin 2 feet wide by 4 
feet long. The inlet and outlet tiles extended through the respective 
bulkheads. A piezometer was installed at the outlet of the catch- 
basin, another at a point 2 feet below the outlet, and a third at a 
point 2 feet below the second. Tests were made with and without 
the use of a 12 to 8 inch reducer at the outlet of the catch-basin. 
This reducer actually consisted of two sewer-pipe reducers (12 to 10 
inch and 10 to 8 inch), each 2 feet long. When the reducer was 
used the middle piezometer was omitted. 
Table 10. — Effect of reducers on the loss of head at outlets of catch-basins. 
Elevation of water surface 
without 
Elevation of water surface 
Drop 
in 
catch- 
basin. 
Grade 
oftUe. 
reducers. 
■R-ith reducers. 
Head 
saved by- 
use of" 
reducers. 
In catch- 
basin. 
2 feet 
below 
catch- 
4 feet 
below 
catch- 
Loss of 
head. 
In 
catch- 
basin. 
4 feet 
below 
catch- 
Loss of 
head. 
basin. 
basin. 
basin. 
Foot. 
Fcr cent. 
Foot. 
Foot. 
Foot. 
Foot. 
Foot. 
Foot. 
Foot. 
Foot. 
0.3 
0.20 
0.46 
0.44 
0.41 
0.05 
0.45 
0.41 
0.04 
0.01 
.84 
.79 
.77 
.07 
.74 
.73 
.01 
.06 
. 75 
.58 
.57 
.45 
.13 
.56 
.52 
.04 
.09 
.97 
.83 
.83 
.14 
.81 
.80 
.01 
.13 
1.50 
.65 
.53 
.49 
.16 
.64 
.53 
.11 
.05 
.78 
.66 
.64 
.14 
.76 
.76 
.00 
.14 
.2 
.20 
.46 
.46 
.45 
.01 
.44 
.43 
.01 
.00 
.83 
.79 
.78 
.05 
. 75 
.74 
.01 
.04 
.75 
.53 
.53 
.52 
.01 
.53 
.52 
.01 
.00 
.76 
.74 
.74 
.02 
.74 
.74 
.00 
.02 
1.50 
.67 
.65 
.53 
.14 
.60 
.56 
.04 
.10 
1.15 
1.02 
.80 
.35 
.82 
.77 
.05 
.30 
.1 
.20 
.44 
43 
.43 
.01 
.45 
.43 
.02 
.79 
.73 
.73 
.06 
.76 
.73 
.03 
.'63" 
. 75 
.56 
.48 
.43 
.13 
.54 
.45 
.09 
.04 
.89 
.68 
.66 
.23 
.80 
.70 
.10 
.13 
1.50 
.68 
.60 
.56 
.12 
.65 
.56 
.09 
.03 
1.11 
.80 
.78 
.33 
.88 
.76 
.12 
.21 
16659^ 
-20— Bull. 854- 
