Sustainability & Green Build
Bushfire Static Water Calculator
Calculates the static water supply volume in litres for bushfire firefighting
Updated 26 June 2026 · Live
What this tool does
Calculates the static water supply volume (in litres) available from a tank or dam for firefighting, from its dimensions and a shape factor.
Bushfire Static Water Calculator — from a tank or dam of length {length_m} m, width {width_m} m and depth {depth_m} m with a shape factor of {shape_factor}, this estimates a static water supply of {result} litres for fire-brigade use.
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Formula Used
How the bushfire static water calculator works
This calculator multiplies length × width × depth to get the volume in cubic metres, applies a shape factor for tapered or irregular tanks, and converts the result to litres. It tells you how much dedicated static water a tank or dam holds for firefighting.
Why a static water supply matters
In bushfire-prone areas many councils and the relevant fire authority require a dedicated static water supply — water reserved for firefighting that is not drawn down by household use. The required volume and the fittings (such as a 65 mm Storz coupling) vary by state, BAL and lot size.
Tanks and dams
For a round tank, enter the diameter as both length and width and use a shape factor of about 0.79 to approximate the circular area. For a farm dam, use the average length, width and depth with a lower shape factor to account for sloping sides.
What this tool does not do
It estimates volume only. It does not set the statutory minimum for your property, specify outlets and fittings, or guarantee access for a fire appliance. Confirm requirements with your local council and fire authority.
Adjusting the defaults
Every input is editable. Enter your own tank or dam dimensions and shape factor and the available litres recalculate instantly.
On-site considerations
A static supply only counts if a fire appliance can reach and draft from it. Position the outlet at a hardstand a truck can park on, fit the coupling your brigade specifies, and keep the reserve isolated from household draw-off with a dedicated tapping or a float that protects the bottom portion. Above-ground tanks in high-BAL zones may need non-combustible construction.
Using this alongside other BuildMetricLab tools
Pair this with the rainwater tank and rainwater harvesting calculators to size the tank for everyday use as well as firefighting, and with the ember guard mesh calculator for the rest of the bushfire package. Every BuildMetricLab tool runs entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Calculates static water volume as length × width × depth × shape factor, then converts cubic metres to litres (×1000). The shape factor de-rates the volume for tapered or irregular tanks. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Is this calculator's result accurate enough to satisfy my council's bushfire water requirement?
Use this as a planning estimate only. Councils and fire authorities set specific static water requirements (litres, fittings, access) under AS 3959 and local planning conditions — always confirm the exact requirement with your local council or fire authority before relying on this figure.
What is a shape factor and why isn't it 1.0?
The shape factor de-rates the simple length × width × depth volume to account for tanks or dams that are not perfectly rectangular (sloped sides, tapered bases, or irregular dam profiles). A prismatic tank with vertical sides uses 1.0; sloped-side dams typically use a lower factor such as 0.85.
Does this replace advice from my local fire authority or council?
No. This tool is a planning estimator only. For bushfire-prone area requirements under the National Construction Code (NCC) and AS 3959, and for fire-brigade access and fittings, consult your local council or fire authority.
Can I use this for a tank instead of a dam?
Yes. Enter the effective length, width and depth of your tank or dam. For a cylindrical or irregular tank, use an equivalent rectangular footprint and adjust the shape factor to approximate the true usable volume.
Spotted something off?
Calculations or display — let us know.
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