Water Supply and Sewage Disposal. 



223 



second compartment by a partition that does not reach 

 the top of the tank. When the first compartment is 

 filled, the sewage runs over the top of the partition and 

 gradually fills the second compartment. In order to 

 prevent the scum from passing into the second compart- 

 ment a baffle board is bolted to the partition in such a 

 manner that its top is above the level of the scum while 

 its bottom dips into the liquid. Some space is left be- 

 tween the baffle board and the partition. 



FIG. 22. A SEPTIC TANK. 



A. drain from the house; B. baffle board to keep the 

 scum (C) from passing into the second compart- 

 ment; D. plug closing the entrance to the drain. 



At any desired time the second compartment is emp- 

 tied by pulling the plug which closes the opening of the 

 drain. The entire contents of the chamber is discharged 

 into the drain at once. The plug should fit tightly so as 

 to prevent constant leaking of sewage into the drains. 

 The second compartment should be of about the same 

 capacity as the first. An overflow pipe is provided so 

 that if the second compartment becomes full, the tank 



