<prompt> Septic tank isAlways double chamberedMinimum capacity is 200galonsDepth is 2-7feetRetention period is 24hours  <response>: 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 