Two-pit composting latrines are best for tropics

The two pit latrine has been proven to be an ideal system for mass sanitation and is widely being promoted in India. But sitting in urban India, try getting some information on how to go about putting one togther and you will hit a wall. Where can you buy the special pans that are central to it? Not easy at all. Maybe my experience will be of some use to others considering building one.

Such a latrine is worth building. Let’s see why. The two pit privy gained acceptance on the basis of two findings. One, if the toilet is flushed with minimal water, there would be no water in excess that would leach out of the pit and enter ground water. And two, the pits must not be located closer than 15′ of a water source such as a well, hand-pump or sump and that the ground water table is atleast 10′ below the pit floor. Of course, rain water should not get into the pits.

Given the above conditions, the two pit system works forever, without any maintenance, producing valuable compost. One pit is first connected and when that is full, discharges are sent to pit-2 while the contents of pit-1 begins to compost. Pits should take six months to fill, and are sized depending on the number of people using. That is enough time in the tropics for organic waste to compost naturally.

The key to the success of this privy is therefore the ability to flush excreta effectively and with little water – perhaps no more than a litre for ablution of the anus and flushing the pan. It is clear the ceramic pans we are all used to in the city will fail in a two pit privy. These pans were introduced in the colonial era as part of water closets imported from England. The floor of these pans have little slope, -they are in fact, almost horizontal- and need a torrent of water. A city’s sewage is carried away in a river of precious water and taken to a central clarifying unit. It is big capital and high technolgy at work here and may be inevitable in dense urban habitats. [But do read this.]

For the two pit privy a special pan was developed. It’s floor has a smooth, deep slope on which little remains to be flushed. The pan also has an s-water trap that keeps the toilet odour free and isolated from organisms in the pit. That enables it to be located close to dwellings.

Polypropylene, a plastic was chosen as the material to manufacture pans in. It is relatively inexpensive, takes good finish, suited for mass manufacture and most of all, far lighter than ceramic pans and therefore easily transported to villages on buses or bicycles. It has been a roaring success with over a million pieces in use. And so why is it hard to find, as i discovered?

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