Rainwater Harvesting System — FarmPal

Capture rain from rooftops and store it for garden irrigation, livestock watering, and with proper filtration, household use. The simplest path to water independence, scalable from a single barrel to thousands of gallons.

How It Works

Rainwater hits your roof, flows to gutters, passes through a first-flush diverter (removes initial dirty water), then fills storage tanks. Water is distributed by gravity or pump. For potable use, additional filtration and UV treatment is added.

Site Requirements

  • •Roof catchment surface (metal roofs ideal, asphalt acceptable for gardens)
  • •Gutters and downspouts in good condition
  • •Level area near downspouts for tank placement
  • •Foundation or pad for tank weight (water = 8.3 lbs/gallon)
  • •Gravity head or pump to distribution points

Components

Gutters & Downspouts
Collect and direct water from roof
$3-8/linear foot
First-Flush Diverter
Discard first dirty water from roof
$20-80 DIY
Leaf Screen/Filter
Keep debris out of tank
$10-50
Storage Tank
Hold collected rainwater
$0.50-2.00/gallon capacity
Overflow
Direct excess water away from foundation
$10-30
Distribution Pump
Pressurize water for household use
$100-400

Sizing Guide

Size storage based on dry-season needs and catchment potential

Formula
Gallons = Roof Area (sq ft) × Rainfall (inches/month) × 0.623 | Storage = longest dry period needs
DIY Minimum
$20 (single salvaged barrel with spigot)
DIY Typical
$500-3,000 (1000-5000 gallon tank system)
Professional
$3,000-15,000 (whole-house potable system)
Annual Maint.
$50-200 (filters, cleaning)

DIY Steps

1
Calculate Potential

Roof area (sq ft) × rainfall (inches) × 0.623 = gallons captured. A 1000 sq ft roof in a 40-inch rainfall area captures ~25,000 gallons/year.

⏱ 1 hour
2
Simple Barrel System (Start Here)

Install a 55-gallon rain barrel at a downspout with a screen and overflow. This is the gateway project that proves the concept.

⏱ 2-4 hours
3
Scaling Up (Tank System)

Install 500-5,000+ gallon storage with proper filtration. IBC totes are cheapest, poly tanks are purpose-built, ferrocement is permanent and can be any size.

⏱ 1-3 days
4
Potable Water Treatment

For drinking water: add sediment filter → carbon filter → UV sterilizer. This three-stage system produces safe drinking water from clean roof catchment.

⏱ 1 day

✓ Pros

  • •Free water only costs are collection and storage
  • •Reduces storm runoff and erosion on your property
  • •Soft water (no minerals) is excellent for plants and laundry
  • •No pumping energy if gravity-fed
  • •Scales from one barrel to whole-house supply

⚠️ Safety

  • •Never drink unfiltered/untreated rainwater
  • •Avoid collecting from treated wood, painted, or old asphalt roofs for any use
  • •Screen all openings to prevent mosquito breeding
  • •Secure heavy tanks against tipping