150│ 3│ 2000│ 8 × 8 │ 6│ 20 175│ 3│ 2330│ 8 × 9 │ 6│ 20 200│ 5│ 1600│ 8 × 12 │ 8│ 20 250│ 5│ 2000│ 10.5 × 12 │ 8│ 20 300│ 5│ 2400│ 12 × 13 │ 8│ 20 350│ 5│ 2800│ 13 × 14 │ 8│ 20 400│ 5│ 3200│ 13 × 17 │ 8│ 20 450│ 5│ 3600│ 13 × 19 │ 8│ 20 500│ 5│ 4000│ 13 × 21 │ 8│ 20 ─────────┴─────────┴─────────┴────────────┴─────────┴───────── The siphons in each instance should be so placed that the lower edge of the bell of the siphon will be at a distance below the roof of the tank equal to twelve inches plus the drawing depth or discharging depth of a siphon of the diameter indicated. There should be three inches of space between the siphon bell and the floor of the chamber. The discharging depths of siphons as used in forming Tables 2, 3, 4, and 5 are as follows: Diameter of Siphon. │ Discharging Depth. │ 3 inches│ 13 inches 5 inches│ 23 inches 6 inches│ 30 inches 8 inches│ 35 inches 10 inches│ 60 inches 12 inches│ 72 inches If the siphons installed are larger or smaller than those shown in these tables, or if the particular make of siphon purchased has the same diameter but a different discharging depth, proper allowance must be made in proportioning the size of the dosing chamber. In order to quickly convey the dose from the siphon chamber to the filter beds at the rate at which the siphon discharges, the sewer from the siphon chamber should be of proper size and should have a sufficient gradient. For instance, with a 3–inch siphon the sewer should be 6 inches in diameter, with a gradient or fall of at least 12 inches per 100 feet; with a 5–inch siphon, the sewer should be 8 inches in diameter, with a gradient of at least 6 inches in 100 feet; with a 6–inch siphon, the diameter of the sewer should be 8 inches, and should have a gradient of at least 12 inches per 100 feet, or 10 inches with a gradient of at least 3 inches per 100 feet; with an 8–inch siphon, 12 inches, with a gradient of at least 12 inches per 100 feet.