While we're exploring sustainable heating and electricity retrofitting solutions, I also want to know more about water reuse solutions. I heard about the Toronto Healthy House and decided to find out more about how it works.

It was built in the early 1990s designed by eco-architect Martin Lieffhebber, it provides all the comforts of home - without using municipal services. It was designed to rely on sun and precipitation as the basis of its heating, electrical, water and waste management systems. The materials and the way they were used in construction mean more comfort, less maintenance and lower operating costs.

The CMHC web site offers practical tips on making your home a healthy house, including using a cystern (water storage tank) to collect and save rainwater for outdoor use, which also reduces use of the community's sewer system.

The question is: what can be done to existing houses to recycle waste water?