On World Water Day, the $80 shower that saves you 250 baths

Hong Kongers have been urged to 'wake up' to their wasteful ways today - UN World Water Day - starting with their shower.

Environmental group Friends of the Earth has calculated that a household of four could save 36,500 litres of fresh water each year - enough to fill 250 bathtubs or grow rice to feed 230 people - simply by installing an $80 water-saving showerhead.

'It's a simple calculation,' said spokeswoman Mei Ng Fong Siu-mei. 'An average showerhead uses about 8 litres per minute, while an aerated showerhead only uses 5.5 litres per minute.

'If you multiply this across Hong Kong's 2.2 million households, it would amount to a saving of 5.5 million litres per minute.'

Taking into account a charge of $3.08 per cubic metre for buying water from Guangdong, $2 per cubic metre for disinfection, and $1.50 for sewage charges, Ms Ng estimates this would amount to a saving of $36,200 per minute.

According to Friends of the Earth, each person in Hong Kong uses about 450 litres of fresh and sea water per day, while the Water Supplies Department estimates that the per capita consumption of fresh water is about 130 litres daily.

Friends of the Earth argues that Hong Kong's low consumption rate - compared with a world average of 1,780 litres per day - is deceiving because the agricultural and industrial sectors, which together account for about 92 per cent of water demand, are mostly located outside Hong Kong.