THE FLOW OF WATER IN DRAIN TILE. 



13 



INTERNAL SIZE OF DRAIN TILES. 



It is generally known that drain tile are not exactly of the 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 

 accurately 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 made 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 measured 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 



ireas of various kinds of tile used. 





l 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 







Com- 



Ac- 







Vari- 

 ation 





Diam- 

 eter 



Area 1 





Diam- 

 eter 



Areai 



Kind of tile. 



Com- 

 mer- 

 cial 

 size 



mer- 

 cial 

 or 

 nom- 



tual 

 meas- 

 ured 

 aver- 



Area 

 com- 

 puted 



Area 

 com- 

 puted 



m 



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 



inal 



age 



col. 3. 



col. 4. 



cols. 



diam- 



eter 



diam- 



eter 





tile. 



diam- 



diam- 



5 



eter. 



in 



eter. 



m 







eter. 



eter. 







and 

 6. 





col. 



8. 





col. 

 11. 





In. 



Feet. 



Feet. 



Sq.ft. 



Sq.ft. 



P.ct. 



Feet. 



Feet. 



So. ft. 



Feet. 



Feet. 



Sq.ft. 



Concrete 



4 

 4 

 5 

 5 

 6 

 6 

 8 

 8 



0. 3333 

 .3333 

 .4167 

 .4167 

 .5000 

 .5000 

 .6667 

 .6667 



0. 3280 

 .3398 

 .4127 

 .4193 

 .4970 

 .5184 

 .6585 

 .6850 



0. 0873 

 .0873 

 .1364 

 .1364 

 .1964 

 .1964 

 .3491 

 .3491 



0.0845 

 .0907 

 .1338 

 .1381 

 .1940 

 .2111 

 .3406 

 .3685 



+3.2 

 -3.9 

 .+1.9 

 —1.2 

 + 1.2 

 -7.4 

 + 2.4 

 -5.5 



0. 3100 

 .3150 

 .3950 

 .3780 

 .4850 

 .4760 

 .6400 

 .6700 



0. 3300 

 .33S0 

 .4100 

 .4510 

 .4850 

 .5260 

 .6450 

 .6720 



0.0804 

 .0837 

 .1272 

 .1349 

 . 1847 

 .1971 

 .3242 

 .3536 



0. 3380 

 .3520 

 .4220 

 .4350 

 . 5130 

 .5350 

 .6770 

 .7360 



0. 3320 

 .3500 

 .4180 

 .4310 

 .4950 

 .5300 

 .6620 

 .7030 



0. 0881 



Hard-burned clay 



.0968 



Concrete 



.1385 



Hard-burned clay 



.1473 



Concrete 



.1995 



Soft-burned clay 



.2227 



Concrete 



.3520 





.4066 





10 

 10 

 12 

 12 



.8333 

 .8333 

 1.0000 

 1.0000 



.8274 

 .8360 

 .9915 

 .9857 



.5454 

 .5454 



.7854 

 .7854 



.5377 

 .5489 

 .7721 

 .7631 



+ 1-4 

 -0.6 

 + 1.7 

 +2.8 



.8080 

 .7950 

 .9630 

 .9700 



.8110 

 .8300 

 . 9780 

 .9760 



.5147 

 .5185 

 .7398 

 .7436 



.8420 

 .8650 

 1.0100 

 1. 0200 



.8410 

 .8400 

 1. 0000 

 .9980 



.5562 



Vitrified2 



.5708 



Concrete 



.7933 



Vitrifiedz 



.7996 







1 Computed as an ellipse. 



2 Tbese tile were in 2-foot lengths; all others in 1-foot lengths. 



