THE FLOW OF 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 

 of tile. 





reducers. 





with 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. 



Per 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 



.03 





.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 



166597°— 20— Bull. 854- 



