Simple rain barrel from a downspout — under $30

A single 55-gallon drum connected to a downspout collects enough water from one rainstorm to irrigate a small garden for a week. This is the cheapest and fastest entry point into rainwater harvesting.

Steps

1. Get a food-grade 55-gallon drum: Check Craigslist, Facebook Marketplace, or local car washes and food distributors. Olive barrels and juice drums are ideal. Cost: $10-20 used, often free.
2. Cut a hole in the lid: Use a jigsaw or hole saw to cut an opening that matches your downspout diameter (typically 3-4 inches). Cover with window screen to keep mosquitoes and debris out.
3. Install a spigot near the base: Drill a 3/4-inch hole 3-4 inches from the bottom. Thread in a brass hose bib ($5-8 at any hardware store) with rubber washers on both sides.
4. Add an overflow port: Drill a second hole near the top and attach a short hose directing overflow away from the foundation.
5. Elevate on cinder blocks: Raising the barrel 12-18 inches provides enough gravity pressure to fill a watering can or run a soaker hose on flat ground.

Tips

• One inch of rain on a 500 sq ft roof section yields ~300 gallons — one barrel fills fast in moderate rain
• Add a few drops of vegetable oil or mosquito dunks (BTI) to prevent mosquito breeding
• Check local regulations — rainwater collection is legal in all 50 states but some have permit requirements for large systems