Plan a rainwater system
Estimate capture, protect the catchment, separate dirty first runoff and maintain covered storage.
Critical caution: Rainwater can contain pathogens, ash, lead, chemicals and animal waste. Collection does not make it potable; assess and treat it for the intended use.
- Time
- 1 day planning
- Difficulty
- High
- Outcome
- Create a protected supplementary water source
Survival lens: Gehring’s homestead lens is combined with modern source protection. Collection, storage and treatment are separate controls; failure in one should not contaminate the others.
Before you begin
- Check local law and building requirements
- Assess roof and tank materials
- Plan overflow away from foundations
What you need
- Roof-area measurements
- Gutter screens
- First-flush device
- Covered tank
- Separate labelled pipework
- Treatment equipment appropriate to use
Step-by-step procedure
- Estimate yield. For each millimetre of rain, one square metre of roof yields roughly one litre before losses. Apply a conservative loss factor and seasonal rainfall, not annual average alone.
- Protect the catchment. Remove lead, asbestos, treated timber, toxic coatings, overhanging contamination and unsafe access. Keep gutters clean.
- Exclude the first runoff. Use a maintainable first-flush system sized to local debris and roof area. Divert contaminated water away safely.
- Screen and cover. Exclude leaves, mosquitoes, rodents, light and surface runoff. Fit a calming inlet and accessible inspection point where appropriate.
- Separate uses. Label non-potable outlets. Prevent cross-connection with drinking-water plumbing. Treat drinking water based on assessed microbial and chemical risk.
- Inspect after events. After bushfire ash, chemical release, bird/animal contamination or roof work, isolate collection and reassess before use.
How to check it is working
- Tank is opaque, covered and insect-proof
- Overflow cannot undermine structures
- First-flush device is emptied and maintained
- Potable and non-potable systems cannot cross-connect
Common mistakes
- Assuming rainwater is automatically clean
- Collecting from contaminated roofing
- Letting tank overflow pool at foundations
- Using one treatment method for every hazard
Sources and further reading
- enHealth (Australian Government): guidance on the use of rainwater tanks
- CDC: How to make water safe in an emergency
- WHO: Guidelines for drinking-water quality
How this guide was checked
Editorial synthesis: Editorial synthesis aligned with enHealth rainwater-tank guidance; treatment still required
Independent specialist review: not yet completed. How review works.
Last updated: Nov 2026 · edition 1.0.
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