A rain barrel under a downspout is one of the cheapest ways to cut your water bill and keep a garden going through dry spells. This guide explains how much water you can expect, what you need, and how to set it up safely.
Check the rules first
Rainwater collection is legal in most places, but some states, cities and homeowner associations set limits on barrel size or how the water may be used. Look up your local rules before you buy anything.
How much water can a roof collect?
A useful rule: each square foot of roof yields about 0.6 gallons for every inch of rain.
| Roof area draining to the barrel | Water from 1 inch of rain |
|---|---|
| 250 square feet | About 150 gallons |
| 500 square feet | About 300 gallons |
| 1,000 square feet | About 600 gallons |
A standard barrel holds 50 to 60 gallons, so a single moderate rain can fill it. That is why an overflow outlet matters.
What you need
- A food-grade barrel with a tight lid, 50 to 60 gallons
- A downspout diverter or a flexible downspout elbow
- A fine mesh screen over the inlet
- A spigot near the bottom
- An overflow hose near the top
- A sturdy, level stand of cinder blocks or treated lumber
Many hardware stores sell kits that include the barrel, screen and spigot.
Set it up in six steps
- Choose the downspout. Pick one near the garden, on firm, level ground.
- Build the stand. Raise the barrel 12 to 24 inches so a watering can fits under the spigot and gravity gives you some pressure. A full barrel weighs over 400 pounds, so the base must be solid.
- Install the spigot and overflow. Fit the spigot a few inches from the bottom and the overflow outlet near the top.
- Connect the downspout. Cut the downspout and attach the diverter or elbow so water flows into the screened inlet.
- Direct the overflow. Run the overflow hose away from the house foundation, toward a garden bed or lawn.
- Test it. Run a hose into the gutter and check for leaks.
Using the water safely
- Do not drink rain barrel water. Roofs carry dust, bird droppings and residue from roofing materials.
- Water the soil at the base of plants rather than spraying leaves and fruit.
- Wash produce with tap water before eating.
- Use the stored water within a week or two to keep it fresh.
Maintenance
- Keep the lid closed and the screen intact to stop mosquitoes from breeding.
- Clean gutters regularly so leaves do not clog the inlet.
- Rinse the barrel once or twice a year.
- In cold climates, drain the barrel and disconnect it before the first hard freeze.
Make the water go further
Mulch around your plants to reduce evaporation, and water early in the morning. If one barrel is not enough, you can link two or more with a short hose near the top.
Water is one part of a larger system. For the full picture, see how to start a self-sufficient backyard.