In Australia, we know the struggles and the fears associated with droughts. It is our most challenging and costly ongoing climate affliction. That is why we desperately stress the importance of saving water.
A waterless composting toilet will save an impressive amount of household water just by not needing to flush the toilet. Then complete the cycle with a greywater system and re-use your household water for irrigation and other non-potable uses.
Litres of water saved annually with a waterless toilet
An already conservative family of four can save 30,000 litres of water
Older toilets (11 litres per flush)
| Average water use per person | 11 litres * 5 flushes = 55 litres/day |
| Average water use per household | 55 litres * 4 people = 220 litres/day |
| Annual water use per household | 22 litres/day * 365 days = 80,300 litres/year |
Modern toilets (6 litres per flush)
| Average water use per person | 6 litres * 5 flushes = 30 litres/day |
| Average water use per household | 30 litres * 4 people = 120 litres/day |
| Annual water use per household | 120 litres/day * 365 days = 43,800 litres/year |
Dual-flush toilets (3 litres per half flush and 6 litres per full flush, use the average 4.5 litres per flush)
| Average water use per person | 4.5 litres * 5 flushes = 22.5 litres/day |
| Average water use per household | 22.5 litres * 4 people = 90 litres/day |
| Annual water use per household | 90 litres/day * 365 days = 32,850 litres/year |
Litres of household greywater that can be reused
Shower
The Australian Government’s Department of Agriculture, Water and the Environment provides estimates on water use. According to their data, a standard showerhead uses approximately 9 liters per minute.
If each household member spends 10 minutes showering per day, that’s:
| Average water use per person | 9 litres/minute * 10 minutes = 90 litres/day |
| Average water use per household | 90 litres * 4 people = 360 litres/day |
| Annual water use per household | 360 litres/day * 365 days = 131,400 litres/year |
Sink
The usage of sinks can be estimated based on various household water use studies. An average rate of about 10 liters per minute is reasonable for many modern faucets.
If the household uses the sink for 15 minutes per day, that’s:
| Average water use per household | 10 litres/minute * 15 minutes/day = 150 litres/day |
| Annual water use per household | 150 litres/day * 365 days = 54,750 litres/year |
Washing machine
Information on washing machine water use is available from water conservation resources and appliance guides. About 50 liters per load is a typical figure for many washing machines.
If the household does 5 loads of washing per week, that’s:
| Average water use per household | 50 litres * 5/7 days ≈ 35.7 litres/day |
| Annual water use per household | 35.7 litres/day * 365 days ≈ 13,035 litres/year |