Septic Tank is a type of on-site system which is connected to the toilet, into which the fecal matter flows after being flushed. An ideal septic tank should have a minimum width of 750 mm and liquid depth of 1 m. The length should be 2 to 4 times the width. The dimensions of septic tank vary with the number of users. (Suitable sizes of septic tank are given in in the Operative Guidelines for Septage Management for Local Bodies in Tamil Nadu, 2014)