GRIDFALLSurvival
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Water · Half day · Intermediate

Rainwater Catchment From Your Roof

Size, plumb and protect a rain barrel system so every storm refills your water reserve.

This is for educational purposes only. Not professional medical, electrical, or safety advice.

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  1. 01

    Estimate your harvest

    Roof area (sq ft) × rainfall (in) × 0.62 = gallons. A 1,000 sq ft roof gives about 620 gallons per inch of rain.

  2. 02

    Raise the barrels

    Set barrels on level cinder blocks. Every foot of height adds pressure for gravity flow to a hose or filter.

  3. 03

    Install a first-flush

    Divert the first 10 gallons of each storm away—it carries bird droppings and roof dust.

  4. 04

    Screen everything

    Cover inlets with fine mesh to block mosquitoes and debris. Keep barrels opaque to prevent algae.

  5. 05

    Treat before drinking

    Roof water is for washing and gardens as-is. For drinking, filter and boil or disinfect.