Rain Barrel Water Harvesting System

Rainwater harvesting is one of the simplest ways to reduce your dependence on municipal water supplies while providing excellent water for your garden. A single 55-gallon rain barrel can fill completely during just one moderate rainfall, providing free water for weeks of garden use.

Project Overview

This project guides you through creating a basic rain barrel system that collects water from your roof's downspout. The system includes debris filtration, an overflow mechanism, and a spigot for easy access to the collected water.

One inch of rainfall on a 1,000-square-foot roof can yield approximately 600 gallons of water. By harvesting even a portion of this, you'll reduce water bills, decrease stormwater runoff, and have a supply of chlorine-free water for your plants.

Tools & Materials

This project requires various tools and materials which are listed in the sidebar. Make sure you have all the necessary items before starting.

Step-by-Step Instructions

1. Prepare the Barrel

1. Clean the barrel thoroughly if it's not new. If repurposing a barrel, ensure it previously contained only food products, not chemicals.
2. Decide which side will be the front (where your spigot will go) and which will be the top (where water enters).
3. Using the measuring tape, mark a spot for the spigot about 3-4 inches from the bottom of the barrel.

2. Install the Spigot

1. Using the drill with a 3/4" bit, carefully drill a hole at your marked spigot location.
2. Apply Teflon tape to the threaded part of the spigot that will go inside the barrel.
3. Insert the spigot into the hole from outside the barrel.
4. From inside, apply silicone caulk around the opening, then secure the spigot with its washer and nut.
5. Tighten with pliers, being careful not to overtighten and crack the plastic.

3. Create the Top Opening and Overflow

1. Mark a 6-8 inch circular or square opening on the top of the barrel for water intake.
2. Carefully cut out this section using a jigsaw or hacksaw.
3. On the upper side of the barrel (near the top but on a side), drill a 1.5-2" hole for the overflow fitting.
4. Install the overflow fitting with Teflon tape and silicone caulk to ensure it's watertight.

4. Install Debris Filter

1. Cut window screen material slightly larger than your top opening.
2. Secure it over the opening to filter out leaves, debris, and mosquitoes.

5. Create a Base and Position the Barrel

1. Create a stable, level base using cinderblocks or a wooden platform. This elevation uses gravity to improve water pressure at the spigot.
2. Position your barrel on the base near your chosen downspout.

6. Connect to Downspout

1. Install the downspout diverter according to its package instructions, typically by cutting a section of your existing downspout and inserting the diverter.
2. Position the barrel so that diverted water flows into your barrel's top opening.

7. Final Steps

1. Double-check all connections for leaks by running water through the system.
2. Consider painting the barrel (with exterior latex paint) to prevent algae growth and increase aesthetic appeal.

Scientific Explanation

Rainwater harvesting works on simple gravitational principles. Water runs down your roof, into gutters, and is diverted into your storage barrel. The raised position of the barrel creates enough head pressure for water to flow through the spigot without pumping.

The water you collect is soft water (low in minerals), making it excellent for plants. The absence of chlorine and other municipal water treatments makes rainwater ideal for sensitive plants and contributes to healthier soil biology.

Rainwater typically has a slightly acidic pH (around 5.6) due to its interaction with atmospheric carbon dioxide, which forms carbonic acid. This slight acidity can actually help make certain soil nutrients more available to plants, especially in areas with alkaline soil.

Alternative Methods

• Multiple Barrel System: For increased capacity, connect multiple barrels in series using short garden hose sections between overflow outlets and barrel inlets.
• First-Flush Diverter: Add a first-flush diverter to reroute the initial rainfall (which contains the most debris) away from your collection system.
• DIY Barrel Alternative: If food-grade barrels aren't available, large heavy-duty plastic trash cans can be modified, though they'll have a shorter lifespan.
• Underground Cistern: For serious water collection, consider underground cisterns, which can store hundreds or thousands of gallons.

Safety Information and Disclaimers

• Water Quality: Rainwater collected from roofs is NOT suitable for drinking without proper treatment. Use harvested rainwater only for irrigation, not for human consumption.
• Mosquito Prevention: Ensure all openings are covered with fine mesh screen to prevent mosquito breeding.
• Child Safety: Secure the lid to prevent children from accessing the barrel.
• Winter Care: In freezing climates, drain the system before winter to prevent ice damage.
• Roof Considerations: Some roofing materials may leach chemicals. Asphalt shingles, treated woods, and some metal roofs might contaminate runoff with substances harmful to certain plants.
• Local Regulations: Some areas have restrictions on rainwater harvesting. Check local regulations before installing your system.
• Structural Concerns: Full 55-gallon barrels weigh over 450 pounds. Ensure your platform is sturdy enough to support this weight.

With proper installation and maintenance, your rain barrel system will provide years of sustainable water access for your garden and reduce your environmental footprint.