THE GARDEN AND THE SEPTIC TANK. 39 



in a gravelly subsoil will dispose of its contents readily, but if it 

 is a neighborhood of shallow wells a cesspool is always a serious 

 menace to health. The only rational way to treat sewage is by means 

 of a septic tank, so that its outflow may become innocuous in every- 

 way. The following* is a simple statement of its construction and 

 operation: 



Sewage should be taken away from the house in a septic system, 

 the most reasonable and sanitary system that there is, and one very 

 inexpensive and easy to make. How this is arranged is shown in the 

 accompanying diagram. 



Construction. The size of these tanks depends upon the number 

 of persons using the system, It is usual to allow four cubic feet of 

 space in each tank for every person using the system. Nine persons 

 therefore will require that each tank contain 36 cubic feet of space, or 

 to be three feet square by four feet deep. The shape of the tanks is 

 of no special importance. 



Both tanks are to be the same size and are placed side by side. 

 The first tank is where the first great activity in sewage change goes 

 on, but in tank No. 2 the final stage of sewage change is accomplished. 

 These tanks are located a little distance from the house and con- 

 nected with the plumbing by glazed terra cotta pipes with well 

 cemented joints. 



A cast iron pipe leads from the terra cotta into the first tank and 

 ends in an ell which projects about 18 inches down into the tank. 

 The outlet of this, las can be seen in the diagram is always closed 

 by the water in the tank. 



On the farther side and near the top of the first tank is another 

 pipe leading to tank No. 2. This also ends in an ell, which sometimes 

 is covered and other times not. The outlet of tank No. 2, however, 

 is at the bottom, although the pipe that removes this water is in the 

 form of an inverted "Y". with the top. where the bend comes, very 

 nearly but not quite as high as the pipe that runs into tank 2. The 

 farther side of the outlet pipe runs down to a lower point than the 

 level of the tanks, and from there has a gradual slope so that it goes 

 off by gravity. 



Operation. By the time the sewage gets through the tanks it is 

 in liquid form entirely so that the work of the final outlet pipe is 

 merely to get rid of liquid. This outlet pipe should run along on a 

 gradual slope until it reaches within about a foot of the surface of 

 the ground. When it reaches this point a "Y" joint of glazed terra 

 cotta is put in and from each arm a line of ordinary porous drain 

 tile laid. These lines of tile must have a very gradual slope, say 

 one-fourth inch in 30 feet. Each line should be about 30 feet long 

 in light soil and 75 or more in heavy soil. 



The tiles must be placed about a quarter of an inch apart so that 

 the liquid will wash out between them, -and rocks, shells, or some 



* From a fuller account of disposal of house wastes in Pacific Rural Press of Dec. 

 21, 1912, and Jan. 25, 1913. 



