>Fig. 25.—Typical two-chamber concrete septic tank. (See table for dimensions and quantities for different sizes.)
Three types of sewage siphon are shown in [figure 26]. In all, the essential principle is the same: A column of air is entrapped between two columns of water; when the water in the chamber rises to a predetermined height, called the discharge line, the pressure forces out the confined air, destroying the balance and causing a rush of water through the siphon to the sewer. The entire operation is automatic and very simple. The siphons shown are commercial products made of cast iron; they have few parts and none that move, and the whole construction is simple and durable. The table ([fig. 26]) lists stock sizes adapted to farm use. Manufacturers furnish full information for setting their siphons and putting them in operation. For example, take type 2, [figure 26]: (1) Set siphon trap (U-shaped pipe) plumb, making E (height from floor to top of long leg) as specified; (2) fill siphon trap with water till it begins to run out at B; (3) place bell in position on top of long leg, and the siphon is ready for service. Do not fill vent pipe on side of bell.
| Type 2 INCHES | |||||
| Diameter of siphon | A | 3 | 3 | 4 | 4 |
| Diameter of outlet | B | 4 | 4 | 4 | 4 |
| Drawing depth | C | 13 | 15 | 14 | 17 |
| Depth to floor | D | 16¼ | 18¼ | 17¼ | 20¼ |
| Height above floor | E | 7¼ | 9¼ | 8¾ | 11¾ |
| Clearance under bell | F | 2 | 2 | 2 | 2 |
| Inside bottom of outlet, to discharge line | G | 20½ | 22½ | 22¾ | 25¾ |
| Discharge line, to top of wall | H | ||||
| Depth of outlet sump | I | ||||
| Length and width of outlet sump | J | ||||
| Diameter of carrier (R), and minimum fall (S) in feet per 100 feet
| R | 4 | 4 | 4 | 4 |
| S | 2 ft. | 2 ft. | 7 ft. | 8 ft. | |
| R | 5 | 5 | 5 | 5 | |
| S | 1½ ft. | 1½ ft. | 2 ft. | 2½ ft. | |
| R | 6 | 6 | 6 | 6 | |
| S | 1 ft. | 1 ft. | 1 ft. | 1 ft. | |
| Type 3 INCHES | Type 1 INCHES | ||||||
| Diameter of siphon | A | 3 | 3 | 4 | 4 | 4 | |
| Diameter of outlet | B | ||||||
| Drawing depth | C | 13 | 15 | 14 | 17 | 5 | |
| Depth to floor | D | 17 | 17 | 19 | 22 | 15 | |
| Height above floor | E | 13 | 13 | 15 | 18 | 19 | |
| Clearance under bell | F | ||||||
| Inside bottom of outlet, to discharge line | G | 19 | 21 | 20 | 25 | ||
| Discharge line, to top of wall | H | 6 | 6 | 8 | 8 | ||
| Depth of outlet sump | I | 13 | 13 | 11 | 12 | ||
| Length and width of outlet sump | J | 18 | 19 | 19 | 18 | ||
[Transcriber Note: The data for Type 1 Siphon has been added to the table.]
Fig. 26.—Three types of sewage siphon. The table gives dimensions for setting standard 3 and 4 inch siphons; also the appropriate size and grade of the sewer to carry the siphon discharge.