Designing a Whole-House Rainwater System

While simple rain barrels are a great start, comprehensive rainwater harvesting can supply water for irrigation, toilet flushing, and even laundry with proper treatment. Here's how to design an advanced system:

System Components:

• Collection surface: Roof area (calculate square footage)
• Conveyance system: Gutters, downspouts, and first-flush diverters
• Storage: Tanks or cisterns (above or below ground)
• Distribution: Pumps, pipes, and filtration systems
• Treatment: Filters and purification for indoor use

Sizing Your System:

To determine potential rainwater collection: Square footage of roof × Annual rainfall (inches) × 0.623 = Gallons per year

A 1,000 square foot roof in an area with 40 inches of annual rainfall could collect approximately 24,920 gallons per year—enough for most outdoor irrigation needs and some indoor non-potable uses.

For those starting small, our guide on building a rain barrel offers an excellent entry point to rainwater harvesting.

The EPA WaterSense program provides comprehensive resources on rainwater harvesting calculations and best practices for residential applications.

Multi-Barrel Connection System

Expand your capacity by connecting multiple barrels for increased storage without taking up more footprint space:

Materials Needed:

• 2-4 food-grade barrels (55-gallon recommended)
• PVC pipes and fittings (1.5-2 inch diameter)
• Uniseals or bulkhead fittings for watertight connections
• Screen filters for each barrel inlet
• Overflow piping system

Construction Steps:

1. Position barrels on stable, level platform (cinder blocks work well)
2. Install connection fittings near bottom of each barrel
3. Connect barrels with PVC piping using a slight downward slope
4. Install overflow pipe from the final barrel to direct excess water away from foundations
5. Add mosquito-proof screen to all openings
6. Connect downspout to first barrel with first-flush diverter

Understanding Greywater Sources and Quality

Greywater is gently used water from showers, baths, bathroom sinks, and laundry. With proper handling, it's perfect for irrigation and can reduce fresh water use for landscaping by up to 50%.

Greywater Quality by Source:

• Bath/shower water: Generally low in contaminants, good for irrigation
• Bathroom sink water: Low contamination, but may contain toothpaste residues
• Laundry water: Quality depends on detergent used—choose plant-friendly options

Research published in the Journal of Ecological Engineering has demonstrated that properly managed greywater irrigation can support healthy plant growth while reducing freshwater consumption significantly.

Simple Laundry-to-Landscape Greywater System

This beginner-friendly system redirects washing machine water directly to your landscape without complex filtration:

Materials Needed:

• 3-way valve for washing machine outlet hose
• 1-inch irrigation tubing
• Mulch basins (dig holes around plants and fill with mulch)
• Outlet emitters or soaker hoses
• Optional: Greywater-friendly detergent

Installation Steps:

1. Install 3-way valve on washing machine drain hose
2. Run irrigation tubing from valve to landscape areas
3. Create mulch basins around plants (12-18 inches deep, filled with mulch)
4. Route tubing to deliver water to mulch basins
5. Label all greywater outlets clearly
6. Use plant-friendly, low-sodium, biodegradable detergent

This system can be easily switched between greywater and sewer drainage, making it ideal for beginners or rental properties.

Advanced Branched Drain Greywater System

For more permanent installations, a branched drain system can distribute greywater from multiple sources to various landscape zones:

System Design Principles:

• Use gravity flow—no pumps required
• Size pipes appropriately (1.5-2 inch for residential)
• Include inspection ports for maintenance
• Design with distribution boxes to split flow evenly
• Always discharge below soil surface to prevent contact

This system works well when you can route plumbing from showers and sinks directly to landscape areas with minimal modification.

The National Academies Press. Washington, DC provides detailed guidelines on greywater system design and safety considerations for residential applications.

DIY Water Usage Monitoring System

You can't manage what you don't measure. Creating a simple water monitoring system helps identify waste and track conservation progress:

Simple Monitoring Methods:

• Manual meter reading: Record water meter readings at consistent times daily
• Usage journal: Track activities against water consumption patterns
• Smart meter add-ons: Some utilities offer monitoring devices that connect to existing meters

Advanced DIY Flow Meter:

For those with technical skills, you can create a simple flow monitoring system using:

• Inline water flow sensor
• Arduino or Raspberry Pi microcontroller
• LCD display or data logging to computer
• Alert system for unusual flow patterns (indicating leaks)

This approach helps identify hidden leaks that can waste thousands of gallons annually.

Leak Detection and Prevention Strategies

The average household loses 10,000 gallons of water each year to leaks—here's how to find and fix them:

Common Leak Sources:

• Toilet flappers (often silent leaks)
• Faucet drips
• Irrigation system leaks
• Water heater pressure relief valves

Detection Methods:

1. Conduct a meter test: Turn off all water sources and check if meter still moves
2. Add food coloring to toilet tanks—if color appears in bowl without flushing, you have a leak
3. Inspect irrigation systems regularly for broken heads or wet spots
4. Listen for running water sounds when all fixtures are off

For more home maintenance strategies, see our guide on repairing household items instead of replacing them.

Creating a Whole-House Water Management Plan

The most effective approach integrates multiple strategies for maximum water savings:

Tiered Water Use Strategy:

1. Potable water: Reserved for drinking, cooking, and bathing
2. Rainwater: Used for irrigation, toilet flushing, and laundry
3. Greywater: Supplemental irrigation during dry periods
4. Conservation measures: Low-flow fixtures, behavior changes, and leak prevention

System Integration Tips:

• Design overflow from rainwater systems to recharge groundwater or irrigate additional areas
• Use greywater during periods when rainwater stores are low
• Prioritize water-efficient appliances and fixtures to reduce overall demand
• Create a maintenance schedule for all system components

This integrated approach can reduce municipal water use by 50-75% for many households.

According to the United Nations Water Development Report, integrated home water management systems represent one of the most effective strategies for reducing residential water consumption globally.

Adapting Your Systems Through the Seasons

Effective water management requires seasonal adjustments to maximize efficiency:

Spring:

• Clean gutters and prepare rainwater systems for spring rains
• Inspect and repair irrigation systems before peak use
• Test greywater systems after winter dormancy

Summer:

• Implement shade strategies to reduce evaporation
• Water during early morning or evening to minimize loss
• Use mulch extensively to retain soil moisture

Fall:

• Harvest fall rains to fill storage for winter use
• Prepare systems for freezing temperatures
• Winterize outdoor components to prevent damage

Winter:

• Drain and protect above-ground systems from freezing
• Plan system expansions and improvements for spring
• Monitor indoor water use during colder months

For year-round gardening that complements your water systems, see our guide on growing budget vegetable gardens at home.