About the Water Demand Calculator
Non-potable water demand for toilets, laundry and the garden — the rainwater-suitable uses.
Also known as: non potable demand, rainwater demand calculator, garden water requirement, toilet flushing water.
How to use this calculator
- Enter people, toilet flushes per person per day, litres per flush, washing machine loads per week and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
demand = Σ (non-potable uses per day)
Worked example
Using the values pre-filled in the calculator above:
- People = 4
- Toilet flushes per person per day = 5
- Litres per flush = 6
- Washing machine loads per week = 5
- Garden watering per week = 100 litres
- Car washing per month = 80 litres
the calculator returns:
- Daily non-potable demand: 172.6 litres
- Annual demand: 63.01 m³
- Toilets: 120 L/day
- Laundry: 35.7 L/day