IRRIGATION m FLORIDA. 21 



together as experiment has shown to be necessary. In the Sanford 

 district it has been found that irrigation is accomplished to best 

 advantage when the tiles are placed 18 to 20 feet apart, although 

 wider spacing is used in some cases. If the tiling is placed farther 

 apart the irrigation will be uneven or will take too long. If the tiling 

 is closer, the irrigation will be satisfactory, but the cost will be 

 excessive. 



The actual construction of a tile irrigation system requires con- 

 siderable care and should be left to experienced hands. The follow- 

 ing description of construction is taken from a report made to the 

 Office of Public Roads and Rural Engineering by Milo B. Williams, 

 irrigation engineer, who has had considerable experience in the con- 

 struction of tile systems at Sanford : 



The tile system consists of a water-tight main pipe feeding a series of open- 

 jointed parallel laterals placed 16 to 18 inches below the surface. The mains 

 are located on the highest side or on the ridges throughout the field, so that 

 the laterals slope away from the mains at the proper depth. The mains are 

 of 4 to 5 inch vitrified terra-cotta pipe, which is obtained in 2i-foot lengths, 

 with a bell end. The joints are made water-tight with cement. A stop box is 

 placed at the intersection of each lateral with the main. (PI. I, fig. 2.) 

 Holes are cut in the side of the pipe and a short length of 2-inch steel pipe is 

 cemented into place to form a connection between the main and the head stop 

 box, the laterals leading out from the stop box. This metal pipe also forms a 

 neck into which wooden plugs may be inserted to control the flow of water. 

 Where the main feeds two laterals leading in opposite directions from the same 

 point the stop box is placed in the main line, with the laterals leading out from 

 opposite sides of the box. 



The laterals are built of 3-inch clay draintile (PI. II, fig. 1), which is 

 obtained in 12-inch lengths. The pipe is laid with open joints by placing the 

 short lengths end to end. A shovelful of sawdust or cinders is placed over 

 each joint to prevent the fine sand from working into the line and stopping the 

 pipe. The grades for the lateral trenches vary from a 1-inch to a 3-inch fall 

 per 100 feet. These grades generally are obtained by turning the water into 

 the trenches before the tile is laid, so that the digger can remove all irregulari- 

 ties from the bottom of the trench. The ordinary expense of the Sanford 

 system, however, would appear to justify a more careful method of establishing 

 and maintaining the grades. At the time the system is laid out it would be 

 weir to establish the grades of the laterals by means of a level in the hands of 

 a competent surveyor, and they should be maintained throughout construction. 

 Laterals are spaced 18 to 24 feet apart, but the shorter distance has proved the 

 more satisfactory. 



Stop pockets are placed in the lateral lines at intervals of 100 to 400 feet for 

 the purpose of checking the water in the laterals and thus securing a small 

 pressure in the lines above the pockets. When pockets are used for this pur- 

 pose a weir division wall is inserted near the inlet side containing two metal- 

 lined openings (PI. II, fig. 2), one a 3-inch hole on a level with the tiles entering 

 and leaving the box and the other a 1-inch hole about 6 inches higher. When 

 the water is not to be held in the pipe line above a box the lower hole is left 

 open, so that the water can pass down the line freely. When the water is to 

 be held up the lower hole may be plugged, raising the water to the upper hole, 

 or both may be plugged, causing the water to rise until it flows over the top 

 of the weir wall into the next section of the lateral. The weir wall is placed 



