SANITATION 395 



Figure 306 is a single-chamber tank that has been used 

 where there is a tile outlet. This tank has been used for 

 several years and is satisfactory. The number of chambers 

 in the tank is dependent on the quantity of liquid flowing 

 through the tank, and also to some extent on the nature of 

 the liquid. From creameries and separator rooms, where 

 there is a large quantity of liquid and a comparatively 

 small quantity of waste matter to be destroyed, better con- 

 trol of the current can be had by use of a tank with several 

 chambers, but for disposal of the sewage from an ordinary 

 dwelling a single-chamber tank, properly constructed, is 

 satisfactory — unless the method of disposal of the effluent 

 requires an additional chamber. 



Size of the septic tank. The size of the tank depends on 

 the quantity of the liquid to be handled in a given length of 

 time. Various authorities differ in regard to the length of 

 time that the sewage should remain in the tank, this period 

 varying from ten to thirty-six hours. For' ordinary house 

 sewage twenty-four hours are sufficient. The first chamber 

 in the tank should ; be large enough to hold all the liquids 

 which will be deposited in it for a period of that length. The 

 quantity of water used per person varies from 20 to 100 

 gallons per day. This includes laundry, washroom, toilet 

 room, etc. In the individual dwelling located in the country 

 or small town 30 gallons per person per twenty-four hours are 

 sufficient. Consequently the number of persons multiplied 

 by 30 will give the size of the receiving chamber in gallons. 

 This divided by y}4 will give the size in cubic feet. 



Location of the tank. Unless it is necessary to use a filter 

 in connection with the tank, it is better to place the tank 

 close to the foundation of the house. The sewage can then 

 be discharged into it direct from the cast-iron soil pipe. If 

 it is placed some distance from the house, it is necessary to 

 carry the sewage through pipes that have water-tight joints, 

 to prevent its leakage into the soil. In cold weather the 

 liquid will lose some of its heat in passing through this pipe, 



