Rain Barrel How-To

Harvest the Rain—Right from Your Roof

Collecting rainwater for your garden is a smart idea, no matter what your motivation. Plants like rainwater, because it's naturally soft, and free of chlorine and other chemicals. If drought is a problem where you live, collecting rainwater is a good way to deal with watering restrictions. If you're on a municipal water system, you stand to save a considerable amount of money. You may also find, as I do, that having a rain barrel is a handy alternative to the garden hose.

Rain barrels allow you to take advantage of the bountiful supply of water from your roof.

When you look at the numbers, it's surprising how much water you can collect every time it rains. Just a half inch of rain falling on a 1,000-square-foot roof will yield 300 gallons of water! To get a quick idea how much water the roof of your own house might yield, here's an example. For a modest-sized house, say 30 x 36 ft., with a typical 2 ft. roof overhang, a half inch of rain would yield about 408 gallons of water. That's enough to fill six standard-size rain barrels.

Here's what you need to set up your own rain harvesting system:

1. Gutters and a downspout. If you don't already have rain gutters on your house, this one-time investment is the biggest cost you'll face. High quality gutters can be rather expensive, but even the least-expensive gutter system will suffice. At my house, we have installed a very inexpensive rain gutter on just one side of the house: the east-facing roof. Being plastic, this gutter won't stand up to Vermont's winter snow and ice, so it gets removed in the fall and put back up in the spring. That's all it takes to keep my 60-gallon rain barrel full to the brim almost all summer long.

Rain Barrel Options
Deluxe Rain Barrel 75 gallons	Rain Catcher Urn 65 gallons
Oak Rain Barrel 45 gallons	English Rain Barrel 40 gallons

2. Storage Tank. In arid parts of the country, rainwater cisterns are becoming more and more commonplace. Usually made of either plastic or concrete, they can hold hundreds or even thousands of gallons of water. If you want to start small and keep it simple, consider a wood or plastic rain barrel, which will typically hold from 40 to 80 gallons of water. If you have the space, several barrels can be set up in tandem. Prices vary, but most quality barrels are about about $100 each. For more information, see our Rain Barrel Department.

3. Debris Screen and Lid. A Downspout Diverter makes it easy to direct rainwater right into your storage tank. But before the water goes into your tank or rain barrel, you'll want to use some kind of debris screen to filter out leaves, pine needles and other debris. If you don't filter out this debris, it will accumulate at the bottom of the tank and may clog up the outflow. A removable wire mesh screen is all you really need, either mounted on top of the rain barrel or attached to the end of your downspout.

A well-fitting lid is also important to protect children and prevent mosquitoes from breeding in the water.

We've adapted a popular British downspout diverter—known for its convenience and trim appearance—to fit American downspouts.

4. Distribution Device. For a rain barrel, you need nothing more than a standard spigot or short length of hose installed near the bottom of the barrel, with an on/off valve. Then you let gravity do the work. You can attach a longer hose to reach your garden, or just use the spigot to fill watering cans.

My own rain barrel is around the back of the house. That's where my deck is, and where most of my container plants are. Because I don't have a water faucet on that side of the house, the rain barrel is a big convenience. I just lift the lid and dip the watering can right in. It fills in a matter of seconds and I'm on my way. If you have a very large reservoir, or want to distribute water some distance away, you might consider investing in a small pump.

In many parts of the world, rainwater collection and containment systems supply all or at least a significant part of the water needs for both house and garden. If your primary motivation is to collect rainwater for your garden, you don't need to worry about capturing every inch of rain that falls on your roof. But consider this. If you get about 10-inches of rain over the course of the spring and summer, an average, 1,360-square-foot roof would yield 8,160 gallons of rain water. You have to admit that whether you're in a drought situation or not, it's hard to pass up that much of a free thing!

Kathy LaLiberte has worked for Gardener's Supply since it began more than 25 years ago. She lives and gardens in Richmond, Vt. Read more of her Innovative Gardener essays.