- 500 L A compact tank for garden watering or a small rainwater buffer where space is tight. It is not normally enough for whole-house supply.
- 1,000 L A small urban tank for limited outdoor use or a carefully defined non-potable use.
- 2,000 L A compact urban capacity for garden use, stormwater management or a limited household connection.
- 3,000 L A useful supplementary urban tank where a smaller footprint matters more than long dry-period autonomy.
- 4,000 L A mid-sized supplementary tank for larger gardens or selected non-potable household uses.
- 5,000 L A substantial supplementary tank that can cover garden and selected household uses when roof catchment supports it.
- 9,000 L A larger storage step for high supplementary demand or a low-use property with constrained tank space.
- 10,000 L A common large storage class for substantial supplementary use or as one unit in a linked system.
- 13,500 L A middle step between urban storage and full-size rural tanks, useful where site access or footprint limits apply.
- 15,000 L A large single-tank capacity for substantial demand, or one component of a multi-tank rural system.
- 20,000 L A large storage class for low-demand whole-property scenarios or as part of a linked system.
- 25,000 L A full-size rural tank class often considered for household supply, subject to roof, rainfall and actual demand.
- 30,000 L The largest single-tank class in this calculator, for high storage needs or fewer units in a linked system.
Capacity guide
Rainwater tank sizes
Compare common tank capacities, then use your roof, rainfall and household demand to calculate what will actually work.