Rainwater Harvesting Manual
Comprehensive guide to rainwater collection, storage, treatment, and system sizing.
A comprehensive guide to rainwater harvesting for residential and commercial applications.
System Components — Six Basic Elements
1. Catchment surface (roof) 2. Gutters and downspouts 3. Debris removal (screens, first-flush diverters) 4. Storage tanks/cisterns 5. Delivery system (gravity or pumped) 6. Treatment/purification for potable use
Recommended Roof Materials
- Metal (Galvalume recommended) — Best for collection - Clay/concrete tile — Good option - Slate — Ideal but costly - Avoid composite/asphalt shingles for potable systems due to toxin leaching
First-Flush Diverters — Route the first flow of water away from the storage tank to remove dust, pollen, and contaminants. Recommended: divert 10 gallons per 1,000 sq ft minimum.
Storage Tank Options
- Polyethylene (50–15,000 gallons) - Fiberglass (vertical/horizontal) - Wood (700–37,000 gallons) - Galvanized metal (150–2,500 gallons) - Concrete (poured or prefabricated)
Tank Requirements
Opaque construction to prevent algae, covered with screened vents, accessible for cleaning, on stable level foundation.
Treatment for Potable Use
- 5-micron sediment filter - 3-micron activated charcoal filter - Ultraviolet (UV) light disinfection - Alternative: ozonation, reverse osmosis, chlorination
Water Quality Testing — Test before consumption and quarterly thereafter for E. coli, Cryptosporidium, Giardia, and total coliforms.
System Sizing — Supply must equal or exceed demand. Most installers assume 75–90% capture efficiency due to evaporation, overflow, and splash-out.
Contact Tank Systems for help sizing your rainwater collection system.
Need Technical Assistance?
Our team is ready to help with material selection, system design, and specifications.