Gravity-Fed Rainwater Irrigation: Design Tips for Small Gardens

Building a Rain Basin Gravity Irrigation System

A homeowner wants to collect rainwater in a basin and distribute it through buried PVC piping for subsurface irrigation of a small garden.

Key Design Principles

• Elevate the storage tank: Raise the collection container several feet to create adequate gravity pressure (0.43 PSI per foot of elevation).
• Use a manifold distribution system: Supply header pipes from multiple points along the mainline to equalize pressure across all rows.
• Size piping correctly: 3/4-inch pipe for distribution rows with small-diameter holes drilled at intervals.
• Prevent clogging: Attach short tubing sections to outlet holes to keep soil from plugging the openings.
• Install air vents: Run 2-foot vertical pipe sections at row ends (supported by stakes) to equalize pressure and ensure even flow distribution.

Important Considerations

Gravity systems require careful elevation planning. For larger areas or consistent pressure, consider adding a small booster pump. Always include a screen filter at the tank outlet to prevent debris from entering the distribution lines.