Before reusing water, know what kind it is.
Rainwater and household graywater can both help in a garden, but they are not interchangeable. They come from different places and follow different rules. Water is fussy like that.
Catch the rain your roof can spare
You can guide roof runoff to a tank, or slow it down in planted basins and swales. The University of Arizona's RainScapes guide explains ways to balance garden needs with rain harvesting.
Read the University of Arizona RainScapes guide, or try the roof-runoff calculator.
Reuse water from certain household drains
Arizona ADEQ defines graywater as separately collected water from clothes washers, bathroom tubs, showers, or sinks. Kitchen sinks, dishwashers, and toilets are excluded. Graywater can also carry soaps and salts that some plants do not enjoy.
Check ADEQ's current home graywater guidance before planning a system.
Arizona-specific safety points
- ADEQ says private residential use under 400 gallons per day may be used for household gardening, composting, or landscape watering when its best management practices are followed.
- ADEQ guidance calls for keeping graywater and irrigated soil away from human contact, preventing runoff or standing water, and using flood or drip application rather than spray.
- ADEQ's food-plant guidance is specific: avoid applying graywater to food plants, with a limited exception for trees or shrubs whose edible portions do not contact the graywater.
- Graywater rules are jurisdiction-specific and can change. Check ADEQ's current guidance and local building, wastewater, and health authorities before installation. Larger, commercial, multi-family, or unusual systems may have different requirements.
Arizona guidance checked November 4, 2026. ADEQ's page was marked revised October 9, 2025 when reviewed. Confirm the latest rules directly with the agency before taking action.