An ideal sanitation solution

An ideal sanitation solution | Source: The Hindu-Sept 27 2013 |

In TPPF you revisit a technology developed and fine-tuned in India decades ago and which still continues to be relevant for the sanitation sector, feels  –
S. Vishwanath ideal_sanitation

Of all the countries grappling with a sanitation problem India tops the list. The number of households without access to a toilet and defecating in the open is nearly a staggering 50 per cent of the total households in India, according to the census of 2011. Even where there is a toilet many simply discharge into the open drains and do not ensure safe disposal. Another recent study establishes a distinct link between open defecation and stunting of growth in children, having far reaching implications for a young population.

It is therefore time to revisit a technology more or less developed and fine-tuned in India decades ago and which still continues to be extremely relevant for the sanitation sector. This is the Twin pit pour flush toilet — TPPF.

The whole toilet users world is divided into sitters and squatters. Then there are wipers and washers. The Indian populace is largely squatters and washers. Keeping this factor in mind the TPPF makes use of an Indian squatting pan with a steep slope that uses just 2-3 litres of water to flush and clean. It has a trap with a water seal, usually a minimum of 20 mm. This constant presence of water in the seal ensures that there is no foul smell that comes back into the toilet and that no insects or cockroaches come into the toilet. A 75 mm-90 mm diameter pipe then takes the washed material to an inspection chamber. Here a diversion trap is made wherein at a time one pipe is opened.

These pipes lead to twin pits which are generally honeycombed. A typical pit would be about 1 metre in diameter and about 1.5 metre in depth with a solid cover on top. The washed material from the toilet ends up in one pit at a time.

A pit takes about one year to fill. Once one pit is full at the diversion chamber the pipeline to this pit is blocked and the other pipe is opened to allow the second pit to fill. The distance between the pits is usually at least a minimum of the depth of one pit i.e. about 1.5 m. This of course depends on the space available.

While it takes one year for the second pit to fill, through the process of bacterial action the first pit is sanitised for bacteria, virus and worms. This can then be emptied usually using mechanical evacuation methods such as that of the vacuum trucks called Honeysuckers. The emptied material, especially in rural areas, can be further composted and used as an excellent fertilizer by farmers.

The superstructure of the TPPF can be permanently done with brick or concrete blocks and a roof of sheet or RCC. In other places they can also be temporary with just privacy ensured for use. Typically a TPPF toilet should cost around Rs. 10,000 in most places in India.

Water should be made available only in small buckets of three litres for ablutions as well as for pour flushing. This will ensure that excess water is not poured into the pit.

Pits can be designed in high water table areas with a concrete bed and with a 50 cm sand cushion all around. The pits should also be a minimum distance of eight metres from a water source such as a well or a borewell. Pits can also be lined with charcoal and limestone to further improve performance and remove pollutants.

Experience has shown that a well designed TPPF can provide safe sanitation and containment of excreta and over the life cycle it can also be much safer than toilets connected to underground sewage treatments with no treatment plants which end up contaminating and polluting water bodies such as rivers and lakes.

In urban areas for those without access to sanitation such as construction workers and in rural areas where open defecation is the norm, the TPPF should be pursued and made mandatory for all to use. Skills in its construction can be developed rather easily .

It is time we revisited this sanitation technology seriously and managed it in a safe manner so that all of India becomes open-defecation free, safe sanitation is practiced and the health benefits accrue to all, especially the young generation.

5 responses to “An ideal sanitation solution

  1. Nripendra Kumar Sarma, Guwahati, Assam, India

    Dear All,
    There is no doubt that the Twin Pit Pour Flush Toilet is a one of the best Technological option for Sanitation Solution in Rural Areas. But what about is the ideal distance between such Toilet and the Drinking Water facilities, like Hand Pump, Open Well etc.? In certain locations, 10 – 15 m (depending is followed as the suitable distance, to avoid leaching of waste / pathogenic Bacteria etc. from the pits to the water sources.
    Thanking All and waiting for the Experts Opinion.
    Thanking You
    Nripendra Kumar Sarma
    Guwahati, Assam, India

  2. Dear all
    The article is good and informative. In Indian socio-cultural condition pour flush toilet is the best option for most of the parts- except in hilly and coastal areas.
    Capacity of a pit having 1 m dia and 1.5 depth, used by 5-6 person per day, is normally for 3 years. Filled pit is emptied after 2 years, since second pit is also filled in 3 years. Contents of pit do not require further composting, as it is decomposed completely. It is free from bacterial pathogens , odourless and can be directly used as manure. It can’t be emptied mechanically, as it has very high percentage of solid, due to honey combs in pit and long retention time in pit.
    Pawan Jha

  3. Great to see this post. iDE is using the twin pit design in Cambodia, although to be perfectly honest not all households are choosing two buy two pits. In collaboration with Jeff Chapin (IDEO) we refined this technology to make it more affordable and aspirational for rural farmers. The final product is the Easy Latrine ( . This latrine retails for $35 (only including 1 pit, the second pit is extra), can be purchased as a complete package including transportation, and can be installed by the household itself. All this said, iDE is a huge advocate of the twin pit pour flush latrine and just wanted to let you know the technology is still thriving in some places.

    Nripendra Kumar Sarma – In our experience, there is no standardized distance that a latrine must be from drinking water sources. It depends on the soil, presence of flooding, groundwater depth, and many other things. We have heard anything from 10m – 30m. Unfortunately I think you need to look at the specific flow/seepage rates in your area to determine a safe distance.

  4. I think we are missing a very important aspect. The aspect of cleaning the Toilets as part of maintenance. Are there any guide lines provided on using a particular type of “Toilet Cleaner”.? The ones that are available off the shelf contain harsh chemicals and its reaction when mixed with sewage can change or damage the Quality of the end product(Fertilizer) So, how do we go about from here ?

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