SEWAGE DISPOSAL 



189 



both the creamery and the dwelling is to run it into a septic 

 tank (see Fig. 44, designed by the author) and from 

 this into a net-work of tile laid underground where it 

 will irrigate and fertilize the soil. 



Object of Septic Tank. The main purpose of the 

 tank, as its name indicates, is to thoroughly decompose 

 all organic matter entering it. This is accomplished by 

 numerous species of bacteria, and the tank may be 

 properly designated as a germ incubator. Where the 



Fig. 44. Septic Tank. 



sewage is emptied into underground tile, the tank also 

 serves as a storage, discharging its contents intermittently. 

 This is necessary to force the liquid to all points of the 

 system and to allow time for each discharge to soak away 

 before the appearance of the next. 



Construction of Tank. The general plan of construc- 

 tion is illustrated in Figs. 44 and 45. The tank is located 

 in the ground with the top within a foot or two of the 

 surface. For durability it is preferably constructed of 

 brick, stone or concrete. The tank is so constructed as to 

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