Archive for September, 2013


On the Twin Leach Pit pour flush toilet -TPPF

September 28, 2013

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 % 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. An economic loss of 6.4 % of the GDP amounting to a staggering 53.8 billion US dollars annually was one estimate by the World Bank in 2006 for India. 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- to professionals in the sector.


The whole toilet users world is divided into sitters and squatters.

Then therImagee are wipers and washers. The Indian populace is largely squatters and washers. Keeping this factor in mind the TPPF has been designed. It 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 diameter to 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 mt. This of course depends on the space available.

While it takes one year for the second pit to fill in the meantime through process of bacterial action the first pit is sanitized for most 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 3 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 8 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 also 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.

In safe sanitation lies water wisdom. 


When the rain gods favour- stock up.

September 21, 2013

Monsoon Blessings


Summary:           It is in years of plenty that we should stock up for times of shortage

Many people are moving into a problem solving mode but it needs institutional reinforcement to help achieve maximum benefits.


The major Public Sector undertaking has a very large campus and has a huge water demand. It draws water from the Bangalore Water Supply and Sewerage Board and pays a hefty Rs 60 per kilo-litre for the water. Being water smart, it has set-up a waste-water recycling unit and ensures that all waste-water is treated and reused for non-potable purpose particularly gardening .Lawns are extensive in the campus and is needed for dust suppression. The unit has also set up a huge lake to harvest run-off from its vast land. More than 170 million litres of storm-runoff is stored in this vast lake.

Their attention has turned to the large rooftop areas they have on campus. From 11,500 square metre of roof area, they simply connected the rainwater downpipes and brought it into a small 20,000 litre sump tank. From here they have put a pump to send the water directly into a much larger sump tank which takes water through a Reverse Osmosis unit. This R.O. water is needed for their manufacturing purpose. The investment they had to make was Rs 10 lakhs.  Was the investment worth it?

The benefits translate as follows. They are likely to harvest 10 million litres of water annually. This will result in a savings of Rs 6 lakhs annually. The payback period for the investment is thus less than 2 years. There are other benefits. The embodied energy in alternate water, either from the BWSSB or bore-wells, is roughly 2 units of power per kilo-litre of water. The industry will therefore save nearly 20,000 units of power annually. This also translates as a savings in carbon emissions.

There are other benefits. The harvested rainwater is very soft with a Total Dissolved Solids of less than 50 ppm. This is likely to reduce further as the initial leaching of cement from the sump tank and the pipes become less.  As against this the water they used from bore-wells had a TDS level of nearly 1000 ppm. The life of the membrane used for R.O. now increases. The reject water from the R.O. has fewer salts and can be recycled more easily than before.

The advantage is clear and it is likely that the industry will move quickly ahead to cover all roof-tops with rainwater harvesting systems. This means that over 100,000 square metres can be covered and over 100 million litres of rainwater harvested. No small feat for an industry located in a water scarce city.

A University: The University of Agriculture with a sprawling 1200 acres campus was once outside the city. Now it has become integral and falls within the Corporation Limits. Its water demand for agricultural crops is high. Most of the water comes from bore-wells. These are over exploited and many have gone dry. It has designed for itself a watershed based rainwater harvesting system. Thanks to a bountiful September rain a great amount of water has been collected and allowed to percolate into the ground. Many bore-wells have revived and are humming with water. The University is able to meet its water demands and students and Professors can continue to develop knowledge with experiments on the ground.

Groundwater banks are being created in the city by institutions that occupy large tracts of lands and have large rooftops. These efforts supplement the water delivery to the city and make the city water smart. Things have to be scaled up and more such institutions brought into the rainwater harvesting community. Further deeper understanding of how much water is actually recharged into the ground, what is a reasonable water demand to keep the groundwater banks humming for 2 to 3 years will ensure that the water shortfall in the city is overcome. Creative solutions using knowledge is the hall mark of the city and in this lies water wisdom.


Building bye-laws and sanitation in urban india

September 16, 2013


1. Building bye-laws should recognize and insist on the provision of a rainwater harvesting recharge well within the site.

2. Building bye-laws should also recognize that non-sewered areas will have to make provision for two concrete ring lined pits for sanitation waste. One pit for black water and one pit for grey water. These can be mechanically emptied using vacuum trucks. The pits too should be located within the site of the building and not be allowed to discharge into storm water drains for public safety, health and hygiene.


Building bye-laws help regulate and maintain a certain discipline regarding the management of water and waste-water in urban areas apart from their role as a major urban planning tool.

Some of the good things they do are for example the insistence on identifying a toilet of a minimum dimension in any house construction before approval .In the Bangalore context rainwater harvesting is made mandatory and the building approval plan to be submitted has to show the recharge structure that is to be implemented.

It is surprising therefore that they miss out on some basics and do not refine the old. Take the rainwater harvesting detail that the Bruhat Bangalore Mahanagara Palike insists on. This is how the design looks like, a recharge pit filled with crushed stone and sand with a splash pad on top.



 In the days were sand dredging or mining has caused devastation to rivers and soil why insist on an archaic design that uses sand and gravel inside it? The design by the Bangalore Water Supply and Sewerage Board (BWSSB) is much better, a recharge well with no sand inside it. It works perfectly well and in fact, if the hydro-geology favours, a recharge well can easily become a withdrawal well. This building bye-law for a recharge well instead of a sand filled pit can easily be made mandatory for all the towns in Karnataka.


Sanitation: While building plans sent for approval have to show toilets, unfortunately there is no insistence on clearly indicating how the waste is to be disposed. While larger buildings and apartments have Sewage Treatment Plants made mandatory, the smaller ones do not have to show any system of appropriate waste disposal. Since septic tanks are costly precast concrete ring pits are used commonly as they cheap and easy to install. Unfortunately most buildings make only a single large pit located outside the house on the pavement or even sometimes the roads. This makes it very difficult for future road works or for water supply and sewage lines to be placed when infrastructure finally arrives in that area.

To remedy this situation the building bye-laws should insist that each building have two pits for sanitary waste disposal. One of the pits should be for the toilets and one for the grey water. The pits can have a small PVC pipe fit to the covering lid to enable emptying using the vacuum trucks called Honey-suckers. The pits should accessible and located appropriately to the front or to the side of the building.

 This one insistence in the bye-law can eliminate the scourge of manual scavenging, clean up the storm water drains and improve the hygiene of our small towns dramatically reducing the disease burden.

It is time for building bye-laws to recognize reality and become water wise.