Northern Rivers Rainwater Tanks – Water Usage & Tank Size Calculator

Postcode or suburb (AU)

Roof catchment area (m²)

Total roof area feeding the tank.
Tip: You can measure your roof area using Google Earth’s Path and Polygon tools .

Runoff coefficient

Target autonomy (days without rain)

How many days you want the tank to cover if it doesn’t rain.

Inside water use

Showers — minutes/day

People showering

Dishwasher — washes/day

Washing machine — washes/day

Toilet — single flush/day

Toilet — half flush/day

Hand basin — uses/day

People (drink/cook)

Outside water use

Garden — minutes/day

Car wash — washes/week

Hose hard surfaces — min/week

Drip system — hours/week

Tip: choose from the dropdown if it appears; otherwise just type and click Calculate.

Avg rainfall (mm/yr)

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Harvestable roof (L/yr)

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Daily usage (L/day)

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Net daily balance

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Recommended min tank (L)

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Tanks that meet or exceed your requirement