Your catchment assumptions
Estimated water caught
Per rain event
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Raw roof yield
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Rule of thumb: 1 inch of rain on 1 square foot ≈ 0.623 gallons. The main estimate multiplies that yield by your collection efficiency.
This is planning math, not a promise of potable water. Keep roof materials, local rules, mosquito control, first-flush diversion, overflow routing, and barrel capacity in the plan. Use captured water according to your local guidance.
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