Beginner’s Guide to Rainwater Collection (With Top 7 Benefits)

Half of our country’s homes rely on underground aquifers, which have gradually filled with water over thousands or even millions of years. But over the last century, we’ve been pumping that water to the surface a lot faster than it can naturally replenish.

According to the United States Geological Survey, groundwater depletion is becoming a significant issue in many places. Some communities are facing water insecurity, and thus higher water bills. Lower water tables are also harming the environment in a multitude of ways, including drying wetlands and lakes.

Fortunately, rainwater collection is an excellent and often affordable solution, providing an alternative water supply.

“Rainwater is an amazing resource, and it’s fun to plan ways to use this resource that falls freely from the sky,” says Laura Allen, a founding member of Greywater Action. “It is typically excellent quality and abundant in much of the country.”

Here’s how to know if rainwater collection is right for you, and how to start doing it at your home.

Benefits of Collecting Rainwater

A major benefit of collecting and using rainwater onsite is simplicity. “This compared to your tap water, which falls on your roof, drains to a stormwater drainage system, ends up in a river or a lake, is pumped back into a water treatment plant, cleaned and then pumped back to your house,” says Fouad Jaber, Ph.D., a professor and rainwater specialist with Texas A&M AgriLife.

Other benefits include:

• Conserving groundwater, which also helps wetlands and other ecosystems;
• Lowering utility bills;
• Reducing your home’s dependence on municipal water;
• Providing water for your yard during irrigation restrictions;
• Mitigating flooding and soil erosion through stormwater management.

Keeping rainwater on your site also stops stormwater pollution, Allen says. “When rainwater runs into the storm drain system, it moves pollution from the land into the water, which is harmful to aquatic life,” she says.

Types of Rainwater Collection

There are two main types: roof runoff into rain barrels and cisterns, and surface runoff into cisterns and rain gardens.

“Even if you live in an apartment, or can’t manage a fancy catchment system, [you can] simply set out buckets and bowls to collect rainwater for your houseplants,” says Kim Roman, an author and owner of Square Foot Gardening 4 U. “If you know it’s going to rain, take advantage of this free gift.”

Rain barrels and tanks (aka rooftop harvesting)

This is the most common system. Rainwater from your roof is funneled through your gutter drain spouts into storage tanks — things like a 55-gallon barrel, or an above-ground 500-gallon cistern.

“For the casual gardener, a rain barrel is a great place to start,” says Mary Phillips, head of the Garden for Wildlife and Certified Wildlife Habitat programs at the National Wildlife Federation. These range from easy DIY installs to more complex whole-house systems that filter and disinfect water, then automatically connect it for use in your home.

When determining what size to install, keep in mind a downspout usually collects from 500 to 1,000 square feet of roof. For each one inch of rainfall, Jaber says, that equals 300 to 600 gallons, or six to 12 rain barrels.

Surface runoff collection

Surface runoff collection directs rainwater on the ground into rain gardens. These are dug-out ponds or natural depressions in the land, typically four to eight inches deep.

“Rain gardens can mimic nature’s filtration system and reap a multitude of benefits for your property and the environment,” says Phillips. “Fill them with a combination of native plants.”

Green roofs

Although more complex, green roofs can be a good option for urban environments. In these systems, rooftop vegetation absorbs and stores rainwater. This slows stormwater, reduces the heat island effect, and offers habitat for plants, birds and insects.

Uses for Collected Rainwater

• Flushing toilets;
• Laundry;
• Houseplant, garden and lawn irrigation;
• Cleaning. Rainwater’s natural softness makes it ideal for cleaning windows, mirrors and even your car.

Because rainwater doesn’t contain chlorine (found in tap water) or chemicals, salt and other minerals (found in groundwater), it can be less stressful on plants. But don’t use the water directly on fruit, Jaber says, and wash your vegetables before eating them.

Can You Filter Rainwater To Make It Potable?

Yes.

If you intend to drink it or shower and wash dishes with it, you’ll need to run it through a series of filters and/or a reverse osmosis system, depending on your situation. This gets rid of harmful contaminants like bacteria, parasites and chemicals.

Is Harvesting Rainwater Legal?

Usually. It’s legal in most of the U.S., with some exceptions.

Some states and municipalities require permits and/or restrict the amount homeowners can collect, especially in Western states with drought conditions, like Colorado. In places where there’s an abundance of rain, states (including Texas) encourage it, and even offer incentives for people to collect rainwater.

How To Build a Simple Rain Barrel

A basic DIY rain barrel consists of an elevated plastic drum with a hole in the top for rainwater to enter, and a spigot near the bottom. Don’t forget to cover holes with 1/16-inch mesh screen to keep out mosquitoes.

About the Experts

• Laura Allen is a co-founder of Greywater Action. She spent the last two decades advocating, teaching, researching and writing books about simple and ecological water solutions.
• Fouad Jaber, Ph.D., is a professor and water resources extension specialist at Texas A&M AgriLife. He’s an expert in integrated water resources and watershed management, as well as stream restoration.
• Kim Roman is an author, speaker, teacher and owner of Square Foot Gardening 4 U. As a professional vegetable gardener, she’s especially excited about her volunteer work helping people become self-sufficient through gardening.
• Mary Phillips leads the National Wildlife Federation‘s Garden for Wildlife and Certified Wildlife Habitat programs. As an ambassador for nature, she keeps habitat gardening programs flourishing with sustainable practices and ever-evolving scientific knowledge.