Rainwater Collection Basics for Beginners

Check your local rules first

Rainwater harvesting is legal in most of the US, but some states and localities limit amounts or methods. Check your state and city rules and any HOA covenants before you install anything.

How much can you collect?

A common estimate: about 0.62 gallons per square foot of roof per inch of rain. A 1,000 sq ft roof in a 1-inch rain can yield around 600 gallons, far more than one barrel holds.

A simple setup

1. A food-grade barrel with a tight lid and screen (keeps out mosquitoes and debris).
2. A downspout diverter; a first-flush diverter helps discard the dirtiest initial runoff.
3. A raised, level, stable base (a full 55-gal barrel weighs about 460 lb).
4. An overflow outlet pointed away from your foundation.

Is it drinkable?

Not straight from the barrel. Roof runoff can carry bacteria, bird droppings, and roofing material residue. Use untreated rainwater for gardens, flushing, and cleaning. For drinking, it needs proper filtration and disinfection; see our water treatment guide.

Sources: Ready.gov (Water), CDC (Emergency water supply; making water safe). Last reviewed Oct 2026.