Septic tank is

Septic Tank The main design features of a septic tank are as follows. (1) Capacity : The capacity of a septic tank will depend upon the number of users. A capacity of 20-30 gallons or 21 / 2 -5 c.ft. per person is recommended for household septic tanks. The minimum capacity of a septic tank should be at least 500 gallons. Septic tanks are not recommended for large communities. (2) Length : The length is usually twice the breadth. (3) Depth : The depth of a septic tank is from LS to 2 m (5-7 ft.). (4) Liquid depth : The recommended liquid depth is only 1.2 m (4 ft.). (5) Air space: There should be a minimum air space of 30 cm (12 in.) between the level of liquid in the tank and the undersurface of .the cover. (6) Bottom : In some septic tanks, the bottom is sloping towards the inlet end. This facilitates retention of solids (7) Inlet and outlet : There is an inlet and outlet pipe, which are submerged. (8) Cover : The septic tank is covered by a concrete slab of suitable thickness and provided with a manhole. (9) Retention Period : Septic tanks are designed in this country to allow a retention period of 24 hours. Too long a retention period will result in undue septicity of the effluent whereas too sho a period gives insufficient treatment. Ref : Park 23rd edition Pgno : 760