Chitra Vishwanath and her husband, S Vishwanath, are architects based in Bangalore who use their home on a 30x50 sq ft as their laboratory. The toilet in Vishwanaths' home is dry, it does not use water. Both the solid and liquid waste from the toilets are collected separately and used as fertiliser in the garden. "The squatting pan has two holes for collecting urine and faeces separately. The urine goes in one section of the pot, which is then used directly on larger trees like banana and mango. But for small plants, it is diluted in the ratio of 1:5 or 1:10 depending on the plants,' explains S Vishwanath. At present we are using Indian squat pots, but soon the Ahmedabad-based Sheetal Ceramics is coming up with western style dry toilets, he adds.

Faeces are collected in tin cans lined with thick paper and once a tin is full, its top is also covered with thick paper and left out in the sun for about two weeks to get rid of extra moisture. It is then emptied into a compost bin.The decomposition takes about 6-8 months, after which the compost is ready to be used on plants in the garden. Greywater from the bath and washing machine of guests' toilet is collected in a tank and used for flushing in other toilets. Excess grey water is treated by running it through a reed system grown in large plastic bins on the terrace of the house. Treated water from reed system is then aerated in small ponds that have guppies (fish) that do not allow mosquito breeding.

"Rainwater is harvested and it suffices for drinking for 220 days. We directly drink rainwater, unless it is running off dusty surface. In that case we put it in plastic bottles for 5 hours to get rid of pathogens such as Ecoli. In cloudy weather the bottles are left out for 2 days,' say the Vishwanaths.