Simple steps to harvest rainwater in Texas like a pro Posted on May 15, 2025

Texans know all too well that the weather across the state can be extreme. Droughts are common, but so are powerful storms. What if you could turn those sudden downpours into a free, sustainable water supply?

Rainwater harvesting is for everyone, not just rural homesteads or eco-conscious architects. With a few basic tools, any homeowner can start collecting rain—whether for gardens, livestock, or emergency use. Best of all, Texas law encourages it: permits are not required for residential rainwater systems, and House Bill 645 passed by the 78th Texas Legislature in 2003 prohibits homeowner associations from implementing new covenants banning rainwater harvesting installations.

If you want to learn more about collecting rainwater, check out the many resources on the Texas Water Development Board website, including the Texas Manual on Rainwater Harvesting—but this article explains everything you need to know to get started!

Three essential components for collecting rain

Every rainwater harvesting system, from a single barrel to a multi-cistern setup, relies on three basic parts:

1. Catchment surface (your roof)

Metal, tile, or asphalt shingle roofs work best, but just about any roof material will do. The bigger your roof, the more water you can collect.

2. Conveyance system (gutters and downspouts)

You’ll want clean, sloped gutters—at least 1/16-inch drop per foot—to direct water efficiently, and leaf guards on your gutters are ideal to minimize debris.

3. Storage (barrels or cisterns)

For beginners and small systems, all you need is a 50- to 100-gallon barrel, preferably made of food-grade plastic. Such barrels can be found at your local hardware store or online for as little as $40. If you already have a barrel, conversion kits to add a spigot and overflow valve are also available—just make sure that your barrel is opaque or paint it so sunlight can’t penetrate. Otherwise, you’ll likely find the water in your barrel filled with algae!

Calculate how much water you can collect

There’s nothing wrong with starting out small with a single barrel. But, it’s good to know how much water you could collect if you decide to expand your system in the future. Calculating the volume of collectable water is straightforward: 1 cubic foot is 7.48 gallons, which means that 1 inch of rainfall produces .623 gallons per square foot. This simple formula will tell you the potential volume of water your home can collect in a year. 

Gallons = Rainfall (inches) × Roof Area (sq ft) × 0.623

The Texas Hill Country receives about 32 inches of rainfall yearly, so if you have a 1,000-square-foot roof, assuming around 80 percent efficiency, you could collect about 16,000 gallons annually—enough to fill a swimming pool! And even a single rainstorm can yield hundreds of gallons. For example, a half inch of rain on that same roof will produce about 300 gallons of harvestable water. Depending upon where you live in Texas, you may get more or less rain, and the following map provides a good idea of how much water you can collect annually.

Installing your rain barrel

Now that you know how much water you have streaming off your roof and into your gutters, it’s time to set up your collection system. Here’s what you need:

• Rain barrel with spigot, overflow valve, and covered openings (to prevent mosquitos)
• A raised, level platform for the barrel to make filling watering cans easier (cinder blocks work well, or you can purchase a purpose-built platform)
• Downspout diverter or flexible downspout extension (diverter kits can be found online for $20 to $30)
• Tools (hacksaw, drill, hose clamps, and thread seal tape, depending upon your setup)

Once you have your materials, choose a downspout for your system—ideally one closest to your garden or wherever you plan to use your captured rainwater. Next, cut the downspout and attach a diverter or flexible elbow to route water into your barrel. Then set up your elevated base, secure your barrel to it, and attach an overflow hose to direct any excess water away from the foundation of your house.

Maintaining your system

After installing your system, you’re all set to start harvesting rain. However, to keep the system working well, you’ll want to perform some regular maintenance:

• Clean your gutters seasonally (especially in the spring and fall) to prevent clogs.
• Check for leaks at the connections after heavy rain.
• Use the collected water within 6 to 12 months to avoid stagnation.

Start small, think big

One barrel can be just the start of your rainwater harvesting journey, but you can grow your system to capture more rainwater and tailor it to your use by

• linking multiple barrels for greater capacity;
• adding a pump for drip irrigation, outdoor showers, or a sprinkler;
• installing a first-flush diverter to discard the debris-filled first few gallons of runoff.

Stay tuned for a future rainwater harvesting article that will walk you through the process of designing and building a higher capacity rainwater harvesting system.

Rainwater harvesting isn’t an all-or-nothing project. A single 50-gallon barrel can save more than a thousand gallons per year. In Texas, where water is both precious and unpredictable, every drop you collect is a step toward greater sustainability for the water system that serves your community.

So go grab a barrel, keep an eye on the forecast, and get ready to harvest some rain!

This article is posted in Technology / Weather / Drought / Water Supply / Conservation / Rainwater Harvesting .