A rain barrel catches water that runs off your roof through a gutter downspout and stores it for watering plants later. You can build one cheaply from a used food-grade barrel, a spigot and a few parts, or buy a ready-made kit. Once it is set up, every storm refills it for free.
Quick answer: Set a covered, food-grade barrel on a sturdy, level platform next to a downspout, add a spigot near the bottom, an overflow outlet near the top, and fine mesh screen over every opening. Direct the downspout into the barrel and use the water on your landscape.
Why a rain barrel is worth it
Your roof collects more water than you might think. University of Nebraska–Lincoln Extension gives a simple formula: roof square feet times inches of rain times 0.623 equals gallons. That means one inch of rain on a 1,000-square-foot roof yields about 620 gallons (UNL Extension), enough to fill a 55-gallon barrel many times over.
Outdoor watering is a big part of home water use. The U.S. EPA says the average household uses more water outdoors than for showering and washing clothes combined (EPA WaterSense). Rain barrels also slow down runoff, so less polluted stormwater rushes into storm drains and out to places like Santa Monica Bay. In California, rainwater collected from rooftops does not require a water rights permit under the Rainwater Capture Act of 2012 (California Legislature bill analysis), though other states have their own rules.
What you need
- A food-grade plastic barrel, often 55 gallons, with a lid (never one that held chemicals or oil)
- A brass or plastic spigot with a bulkhead fitting or washers and nuts
- An overflow fitting and a short hose to carry extra water away
- Fine mesh screen to keep out mosquitoes, leaves and debris
- A drill with a hole saw sized to your fittings
- Waterproof sealant or plumber’s tape
- Cinder blocks or a sturdy stand for a solid, level base
- Optional: a downspout diverter or flexible downspout extension
How to set up a rain barrel
- Find a safe barrel. Look for a food-grade barrel that held things like syrup or juice. Many people find them through local businesses or online marketplaces. Rinse it well with soapy water.
- Pick the spot. Choose a downspout near the garden. The ground must be flat and firm, because a full 55-gallon barrel weighs over 450 pounds, according to UNL Extension.
- Build a stable base. Set two layers of cinder blocks or a sturdy stand on level ground. Raising the barrel makes room for a watering can and adds a little water pressure.
- Install the spigot. Drill a hole a few inches above the bottom of the barrel. Fit the spigot with washers on both sides and seal it so it does not drip.
- Add the overflow. Drill a second hole near the top of the side wall and attach the overflow fitting and hose. Point the hose toward a garden bed or away from your home’s foundation.
- Screen every opening. Cut a hole in the lid for the downspout and cover it with fine mesh screen. Seal gaps so mosquitoes cannot get in to lay eggs.
- Connect the downspout. Shorten the downspout or add a diverter or flexible extension so water flows onto the screen and into the barrel.
- Use the water regularly. Water plants between storms so the barrel has room for the next rain.
Tips
- Use rain barrel water on flowers, shrubs, trees and lawns. UNL Extension does not recommend it for fruit and vegetable gardens, and it is not safe for people or pets to drink.
- In Southern California, most rain falls in winter, so use your stored water before the dry months and keep the screen clean.
- Link two barrels with a short hose near the bottom to store more water.
- Before a freeze, drain the barrel and open the spigot so it does not crack.
Frequently asked questions
Is it legal to collect rainwater?
In California, yes. Rainwater collected from rooftops does not require a water rights permit under the state’s Rainwater Capture Act of 2012. Rules vary in other states, so check with your state water agency.
How do I keep mosquitoes out of my rain barrel?
Keep the barrel closed, make connections tight, and cover every opening with fine mesh screen. UNL Extension says this is the most effective way to keep mosquitoes from getting in.
How much water does a rain barrel save?
A standard barrel holds about 55 gallons each time it fills. Since one inch of rain on a 1,000-square-foot roof makes about 620 gallons, a single storm can refill it many times.
Can I water my vegetable garden with rainwater from a barrel?
UNL Extension does not recommend rain barrel water for fruit and vegetable gardens, because roof runoff can carry contaminants. Use it for ornamental plants instead.
See your household water use
How much water does your yard really use? Try our free Household Water Simulator to see your indoor and outdoor water footprint and how a rain barrel and other changes can shrink it.
Related guides
- How to Set a Sprinkler Timer Once and Never Touch It Again
- How to Switch from Sprinklers to Soaker Hoses for Your Garden
- How to Landscape with Native Plants to Cut Water Use
Sources
- University of Nebraska–Lincoln Extension, Stormwater Management: Rainwater Harvesting with Rain Barrels (G2220)
- U.S. EPA WaterSense, Outdoors
- California Legislature, AB 1750 (Rainwater Capture Act of 2012) bill analysis
Written and reviewed by the Accessible Sustainability Alliance editorial team. Last updated October 5, 2026.
