🌧️ Rainwater Harvesting Systems

Rainwater harvesting captures precipitation from your roof and stores it for later use, primarily landscape irrigation. A typical 1,500 sq ft roof can collect 900 gallons from just 1 inch of rainfall. That's free water that would otherwise run into storm drains.

The economics work best in areas with moderate rainfall (25-50 inches/year) where you can capture enough water to meaningfully offset irrigation needs. In very dry areas, collection may be limited; in very wet areas, municipal water is often cheap enough that payback periods are long.

How Much Water Can You Collect?

Collection potential depends on your roof size and local rainfall. Use this formula:

Roof Size	20" Rainfall	30" Rainfall	40" Rainfall
1,000 sq ft	12,000 gal	18,000 gal	24,000 gal
1,500 sq ft	18,000 gal	27,000 gal	36,000 gal
2,000 sq ft	24,000 gal	36,000 gal	48,000 gal
2,500 sq ft	30,000 gal	45,000 gal	60,000 gal

Types of Rainwater Harvesting Systems

Basic Rain Barrel Setup

For most homeowners, rain barrels offer the best balance of cost, effort, and savings:

Components Needed

• Rain barrel: 50-100 gallon container ($80-200)
• Downspout diverter: Connects gutter to barrel ($20-40)
• Overflow hose: Directs excess water away from foundation ($10-20)
• Spigot: Usually included with barrel
• Elevated platform: Cinder blocks or stand for gravity flow ($20-50)
• Mosquito screen: Usually included, prevents breeding

Installation Steps

1. Choose location near downspout, preferably shaded (reduces algae)
2. Build or place sturdy platform (full barrel weighs 400-800 lbs)
3. Position barrel on platform
4. Install downspout diverter (cuts into existing downspout)
5. Connect diverter to barrel inlet with tubing
6. Attach overflow hose directing away from house foundation
7. Ensure mosquito screen is secure
8. Test system with garden hose

Using Harvested Rainwater

Best Uses (Non-Potable)

• Landscape irrigation: Watering trees, shrubs, and ornamental plants
• Garden watering: Vegetables and food crops (safe when applied to soil, not leaves)
• Container plants: Excellent for potted plants - no chlorine
• Lawn watering: Supplemental grass irrigation
• Car washing: Soft water leaves fewer spots
• Outdoor cleaning: Washing outdoor furniture, decks, driveways

Water Quality Considerations

Roof-collected rainwater is generally safe for irrigation but not potable without treatment:

• First flush diverter: Diverts first 10-20 gallons that wash debris off roof
• Filtration: Basic screening removes leaves and debris
• Settling: Sediment settles to bottom; draw water from above bottom
• Avoid stagnation: Use water regularly to prevent bacterial growth

Financial Analysis

Is rainwater harvesting worth the investment? Here's the math:

Rain Barrel System (2 barrels, 100 gallons total)

Item	Cost
2 Rain barrels (50 gal each)	$160-300
Downspout diverters (2)	$40-60
Platforms/stands	$40-80
Hoses and connectors	$30-50
Total Investment	$270-490

Annual savings: If you fill and empty barrels 30 times during growing season = 3,000 gallons = $35-50/year at typical rates

Payback period: 6-14 years (faster with utility rebates of $50-100)

Larger Cistern System (1,000 gallons)

Item	Cost
1,000 gallon tank	$800-1,500
Pump system	$200-400
Filtration/first flush	$100-200
Plumbing and installation	$300-600
Total Investment	$1,400-2,700

Annual savings: 15,000-20,000 gallons captured = $180-300/year

Payback period: 5-15 years (faster in high water-cost areas)

Rebates and Incentives

Many utilities offer rebates for rain barrels:

• Typical rebate: $25-75 per barrel (some offer free barrels)
• Large system rebates: Some areas offer $500-5,000 for cisterns
• Tax credits: Arizona, New Mexico, Texas offer tax incentives

Check your water utility's website or call their conservation department. Some cities hold annual rain barrel sales with deeply discounted barrels.

When Rainwater Harvesting Makes Sense

Good Candidates

• Areas with 25-50 inches annual rainfall
• Properties with moderate-size gardens or landscapes
• Homeowners who enjoy gardening and hands-on projects
• Regions with high water costs ($0.01+/gallon)
• Properties where rebates significantly offset costs

Not Ideal For

• Very arid climates (under 15 inches rain) - not enough to collect
• Very wet climates with cheap water - long payback periods
• Homeowners wanting "set and forget" solutions
• Properties with limited space for tanks
• Those primarily concerned with ROI (smart controllers have faster payback)

Combining with Other Systems

Rainwater harvesting works best as part of a comprehensive water strategy:

• Smart irrigation: Use harvested water with weather-based controllers for maximum efficiency
• Drip irrigation: Low-pressure drip systems work well with rain barrel gravity flow
• Drought-tolerant plants: Combine with native landscaping that needs less supplemental water
• Mulching: Reduce evaporation so harvested water goes further

Maintenance Requirements

Rain harvesting systems require minimal but regular maintenance:

Monthly

• Check mosquito screens for damage
• Inspect overflow path is clear
• Verify spigot isn't leaking

Seasonally

• Clean gutters (debris clogs system)
• Flush sediment from bottom of tank
• Check diverter for blockages
• Inspect tank for cracks or damage

Annually

• Deep clean tank interior (especially before winter)
• Replace any worn gaskets or seals
• Check structural integrity of platform

Frequently Asked Questions

Is rainwater harvesting legal in my state?

Most states allow it, but some have restrictions. Colorado allows up to two 55-gallon barrels. Check your state's water rights laws. Generally, states east of the Rocky Mountains have few restrictions.

Can I drink harvested rainwater?

Not without proper treatment. Roof-collected water contains bird droppings, debris, and potential contaminants. It's excellent for irrigation but not potable without filtration, UV treatment, and testing.

Will my HOA allow rain barrels?

Many states now have laws protecting homeowners' rights to harvest rainwater, overriding HOA restrictions. Check your state laws. If no protection exists, submit a proposal showing attractive, well-maintained barrels.

Do rain barrels attract mosquitoes?

Only if improperly maintained. Secure mosquito screening on all openings prevents breeding. Use water regularly so it doesn't stagnate. Consider adding mosquito dunks (Bti) that kill larvae but are safe for plants.