What is rainwater collection?
Rainwater collection means capturing water that runs off a roof, usually into gutters, a screen and a storage tank. It has been done for centuries and is common in dry regions and on farms.
The simplest form is a barrel under a downspout for garden use. More complex systems store large volumes for animals, irrigation, firefighting reserves or household use, and they need much more design and care.
A single roof can yield surprising amounts of water from a modest rain, which is why even small systems need an overflow path that does not erode soil or flood a basement.
Is it legal where you live?
Rules differ widely. Some states encourage collection, some set limits on how much you can store, and some regulate how it can be used. Local building and health departments may have additional requirements.
Check with your state water agency and your county health department before you build. Do not rely on neighbors' guesses or on a rule you half remember, since some places have unexpected restrictions.
Ask also about permits for tanks, since size, height and placement may be regulated, especially for buried or large tanks.
- State water agency
- County health or building department
- Homeowners association rules, if any
What can you use the water for?
Garden watering, washing tools and livestock watering are the most common uses. Drinking and cooking are possible only with proper treatment and testing, and whether it is allowed depends on local health rules.
Rainwater picks up dust, bird droppings, leaves and roof materials. It can contain germs and contaminants, so do not drink it untreated. Ask your health department what treatment and testing are appropriate.
Livestock generally tolerate rainwater better than people do, but algae and dead animals in a tank can still make animals sick. Check tanks regularly and clean them on a schedule.
How does the roof and collection system affect quality?
Your roof is the first filter. Some materials, such as certain treated or coated surfaces, may not be suitable for collecting water you plan to use around food. Roofs near trees collect more leaf litter, and flat or damaged roofs hold more debris.
Gutters, screens, a first-flush diverter and a covered tank help keep debris out. Keep screens cleaned, trim overhanging branches, and inspect the system after storms.
Inspect your gutters in spring and fall, and after any heavy wind. A blocked gutter sends water over the edge instead of into your tank.
How should you store and protect stored water?
Tanks should be opaque, covered and screened to keep out light, insects and animals. Light encourages algae and open tanks invite mosquitoes. Use only food-grade materials for tanks that hold water for uses involving people or animals.
Place tanks on a firm, level base, since full tanks are very heavy. Plan for overflow so water drains away from foundations and buildings.
Consider a tank with a lid you can open for inspection and cleaning, and a fine screen on every opening. Mosquito breeding is a real health concern in warm weather.
How does it fit with a well or other supply?
Rainwater can supplement a well, but never connect a rainwater system to your household plumbing without guidance, because cross-connection can contaminate drinking water. Plumbing connections often require a licensed professional and permits.
If you have a private well, test it on the schedule your health department recommends. The EPA provides information on private wells, and rainwater should not replace regular testing.
Keep a log of rainfall, tank levels and maintenance so you learn how much your system truly supplies in your climate.
What should you plan for in dry spells and freezes?
A tank only holds what falls, so a long dry spell may leave it empty. Keep a backup supply, and treat rainwater as a bonus rather than your only water unless the system is designed for that.
In cold climates, freezing can crack tanks, pipes and fittings. Drain and protect equipment before winter, and ask your extension office about local practice.
After any long dry spell, flush the first rainfall away from the tank rather than letting dust and debris wash in. Many systems include a diverter that does this automatically, and it deserves regular checking.
Key takeaways
- Check state and local rules before installing a rainwater system.
- Do not drink untreated rainwater.
- Use screens, covered tanks and regular cleaning to protect quality.
- Never connect a rainwater system to household plumbing without professional guidance.
- Keep a backup water supply, because tanks run dry in long dry spells and can crack in hard freezes.
Sources and further reading
Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.