Rainwater catchment calculator
How many gallons can your roof legally collect each year in Arizona? Plug in your roof size and your local rainfall — we'll do the math.
Result
- Annual catchment
- Monthly average
Where the 0.623 comes from. Each inch of rain falling on one square foot of roof yields 0.623 gallons (after accounting for spillover and surface tension losses). So roof × rain × 0.623 = gallons per year.
Arizona is rainwater-friendly. AZ explicitly allows rooftop rainwater harvesting for non-potable use (irrigation, toilets, cleaning). Some counties allow potable use after filtration. Always first-flush divert and screen your inlet — the first ½ inch of rain carries roof debris.
Recommended gear
Affiliate links — Plotnode may earn a commission from purchases at no extra cost to you.
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AmazonRain barrel downspout diverter kitFits 2"x3" or 3"x4" downspouts with built-in filter and brass spigot.
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AmazonRain Harvesting first-flush diverterCatches the first dirty inch of rainfall before clean water hits your storage. Critical for potable systems.
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AmazonHeavy-duty 100-gallon water storage bladderStainless steel fittings, leak-proof, portable. Great catchment buffer or emergency backup.
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