Are rain barrels effective?

Using rainwater collected in rain barrels is a good idea for many reasons. It's relatively pure and soft, making it good for nondrinking uses; and because it isn't treated with chemicals like tap water, it's better for your plants.

Water usage is restricted in times of drought, but you'll have more freedom for things like washing your car if you collect rainwater. Using rainwater as a supplement will help reduce utility bills and reduce the number of groundwater resources that are drained. In addition, it will leave more water -- that you might otherwise be taking from the tap -- for your local ecology, to help sustain wildlife in the lakes and rivers.


When rainwater runoff gets polluted from things like antifreeze and oil on the roadways, it then continues flowing into creeks and streams, polluting them. If you catch some of this rainwater before it gets tainted, you'll be preventing some of this pollution.

To calculate how much rainwater you can expect to collect, use this formula:

  1. Measure the length and width of your home's exterior (plus roof overhang).
  2. Multiply the length by the width to find your home's roof catchment area.
  3. Multiply the roof catchment area by 0.6 (the portion of a gallon that can be harvested when an inch (2.5 centimeters) of water falls on a square foot (0.09 square meters) of roof area.

The resulting product is how many gallons of water your roof catchment area will yield from that one inch (2.5 centimeters) of rainfall. (Multiply this number by 3.8 to find out how many liters it will yield.)

Never leave your rain barrel uncovered. Not only do you want to keep debris and insects from falling in, but exposure to open air and sunlight encourages algae growth. And children can drown in just two inches (five centimeters) of water [source: Westcovina], so use every precaution.