Every person in the world who lives in a house has their own, private, water supply: rainfall on their roof. I can’t explain why people in other countries don’t use rainwater tanks – it’s probably because water from other sources is cheap and plentiful – but in Australia, the world’s driest inhabited continent (Antarctica is the driest), only 7% of capital city households have rainwater tanks and only 13% of all households use them for the main source of drinking water, according to the Australian Bureau of Statistics.
Throughout the 20th century, mains water supply in Australia’s cities and towns had to be installed and paid for, and so it became compulsory for all. Rainwater tanks were prone to backflow into the mains water supply. People who retained them preferred to use this water for free rather than purchase mains water. Although rainwater tanks were never banned, governments made it nigh impossible to install them where mains water was provided. Only in the last several years have some state governments (New South Wales and Victoria) relaxed town planning laws allowing small rainwater tanks to be installed in urban areas without planning approval.