Engineering reference · AU domestic water
The Australian guide to smarter home water systems
Understand how rainwater moves through your property, how tanks fill, and how climate shapes water availability — explained as engineering concepts, not products or services.
Sheet00 / INDEX
ScopeDOMESTIC
RegionAUSTRALIA
TypeEDUCATIONAL
FIG 01
How the reference is organised
Each module isolates one part of the domestic water system and explains the underlying logic. Read them in any order — or run the estimator first to see how the variables interact.
MOD 02
Rainwater tanks
How catchment, downpipes, first-flush and overflow combine into a working storage system.
MOD 03Tank sizing logic
Why roof area, rainfall variability and household demand together set a sensible storage range.
MOD 04Greywater concepts
What greywater is, where it comes from, and the principles behind safe, lawful reuse.
MOD 05Water quality
How roofs, debris and storage hygiene shape rainwater purity and when treatment matters.
MOD 06Regional rainfall
Rainfall patterns across seven Australian cities and what they mean for storage.
MOD 08Maintenance
Inspection, cleaning and filter-care cycles that keep a system performing.
FIG 02
The home-scale water cycle
At the scale of a single home, the water cycle is short and legible. Rain falls on a roof, runs to gutters, drops through downpipes, and either enters a tank or leaves as stormwater. What you capture depends on three things working together: how much rain arrives, how much of it your roof can collect, and how much you can store before the tank overflows.
The reference treats each of those as an adjustable variable rather than a fixed answer. A large roof in a dry climate can out-collect a small roof in a wet one; a generous tank is wasted if inflow never fills it. Understanding the relationships is more useful than any single number — which is exactly what the estimator is built to show.
Reading note
Every figure on this site is conceptual. Real systems depend on local rainfall records, roof condition, plumbing and regulations that vary by council and state.
FIG 02.1 — capture relationship
Illustrative chain from rainfall to usable capture for a typical roof + system.
FIG 03
Why region changes everything
Average annual rainfall varies almost threefold across Australian capitals — and the timing varies even more. The same tank behaves very differently in monsoonal Darwin than in winter-rainfall Adelaide.
FIG 03.1 — mean annual rainfall by capital (mm)
1730Darwin
1150Sydney
1010Brisbane
730Perth
615Hobart
600Melbourne
545Adelaide
Long-term averages, rounded. Explore seasonal patterns on the regional rainfall module.