A twin-pit is a containment structure that has two cylindrical pits connected to each other through a pipe. When one pit gets filled with human waste from toilets, then the connection to the filled pit is closed, and the toilet pipe is connected to the second pit to collect the human waste. The distance between two pits should be at least 1 meter. By the time the second pit is filled, the partially treated human waste from the first pit is emptied, and made available for collection of human waste.
Figure 8: Twin-pit
Source: (Sulabh International Social Service Organisation, 2015)