38 



BULLETIX 57, U. S. DEPARTMEXT OF AGEICULTUKE. 



This tank is suited to flat ground where outlet fall is difficult to obtain, 

 as \rill be noted by the difference in elevation between the floors of the 

 two chambers. For satisfactory operation a small septic tank should 

 not be built of smaller size than for six persons. 



LOCATIOX AND COXSTRUCTION. 



The septic tank, although air-tight and supposedly water-tight, 

 should be located as far from the house and the well or spring as con- 

 venience and local surroundmgs will permit, thus reducing the danger 

 of pollution or nuisance in case of leakage or improper operation of 

 the system. 





C<7p<?o/^ 320^<:7/. 



{6\ 



^y^<fcj^yi:Kxu 



=D 



I _ ^ _ 



Fig. 30. — Double chamber septic taak for family of si;c people, suitable to conditions where outlet fall is 



difficult to obtain. 



The sewer from the house should be of vitrified sewer pipe, usually 

 of 4 inches size, ^vith tightly cemented joints, and should be laid to 

 a grade not less than 9 inches per 100 feet. Where the fall from 

 the house to the tank is excessive, it is a good idea to lay the last 100 

 feet of tile to the minimum grade to break up entrance velocity. 



It is assumed that the farmer has a working knowledge of small con- 

 crete structures.^ The septic tank should be constructed as nearly 

 water-tight as possible, preferably of concrete. The walls should be 

 6 or 8 inches thick, the floor 4 to 6 inches thick, and the roof about 

 6 inches thick and reenforced. Some means should be provided at 

 the bottom to facilitate the cleaning out of settled sludge. Either 

 the floor may be sloped toward the inlet end for this purpose or a pipe 



1 



1 U. S. Dept. Agr., Farmers' Bui. 461. 



