DRAINAGE METHODS FOR COUNTY ROADS. 
33 
water to be drained off, the diameter of the tile never should be less 
than 4 inches, because experience has shown that tile having a smaller 
diameter is very liable to become obstructed by sediment. The larger 
diameters given in the table generally are used only where it is neces- 
sary to admit more or less surface water directly into the tile, or to 
provide for some unusual flow from springs. 
CLAY TILE. 
Clay tile of the diameters shown in Table 4 is manufactured in 
almost every section of the United States. The ordinary farm tile, 
without the bell joints, is the kind most generally used f or subdraining 
roads, and is generally satisfactory when laid at the side of a road 
where it will not be subjected to heavy loads. The tile may be either 
round or hexagonal in cross section and should be straight longi- 
tudinally, well burned, and free from cracks. The nominal section 
lengths are 12 inches for the smaller sizes and 2 feet or 2 feet 6 inches 
for the larger sizes. In practice, the lengths generally are made 
slightly in excess of the nominal to allow for a small amount of break- 
age. The ends always should be cut square in manufacturing so that 
successive sections may fit together snugly, but seldom does this con- 
dition exist. To make a good fit it is necessary at the time of laying 
to turn the tile over until the ends make the snuggest joint. If the 
cost of bell tile is not prohibitive they may be used to advantage in 
place of butt-joint tile. 
Table 8 gives the average weight and the average number of feet 
in a carload for the various diameters of field tile. The costs at the 
factory are subject to more or less variation, and freight charges on 
tile have been relatively high, so that the costs of pipe delivered at 
railroad points some distance from the factory are so constantly 
variable that tabular figures are of little value. Where more than one 
size of tile is shipped at the same time, the amount in a carload may 
be increased and the freight per ton decreased by nesting the differ- 
ent sizes. 
Table 8. — Cost and weight of drain tile. 
Inside diameter. 
Average 
cost per 
1,000 feet 
f. o. b. 
factory. 
Average 
weight 
per foot. 
Average 
number 
of feet 
in a 
carload. 
Inches. 
4 
$15. 00 
22.50 
27.50 
47.00 
67.00 
Pounds. 
8 
10 
12 
18 
28 
6,500 
5,000 
4,000 
2.500 
1,600 
5 
6 
8... 
10 
Inside diameter. 
Average 
cost per 
1,000 feet 
f. o. b. 
factory. 
Average 
weight 
per foot 
Inches. 
12 
$95. 00 
140. 00 
245. 00 
370. 00 
Pounds. 
36 
50 
72 
115 
15 
18 
24... 
Average 
number 
of feet 
in a 
carload. 
1,000 
700 
400 
300 
66998°— 18— Bull. 724- 
