Rain Harvesting: How to Make a Rain Barrel Work for Your Garden

Enlarge Image Image Gallery Turn that next downpour into a weeklong supply of water for your sprouting tomatoes. illustration by Nate Skow

Middle America gets hot in the summer. Try as we might to prevent that cracked-earth look in the garden, the amount of water one would use to keep a large amount of garden soil moist in July and August would be pretty pricy. Placing any number of rain barrels underneath downspouts, a bit of rain harvesting, could make all the difference for your garden irrigation expenses.

Many folks don’t realize that both topsoil and subsoil can store quite a bit of water, or that plants can then make use of that soil-stored water over time. In most areas, for much of the year, the topsoil and/or subsoil may not be saturated with water – which means there’s unused storage capacity down there. Using our design, you can enhance the effectiveness of your rain barrel by creating an irrigation attachment that will deliver rainwater from the roof to your garden or lawn in quantities that could easily double the effective rainfall in those areas – recharging the localized soil-water content in the process. 

Materials List:

1. 2-inch PVC or ABS bulkhead fitting with 2-inch female pipe thread in outer flange.
2. 2-inch by 4-inches long TBE pipe nipple with 2-inch male pipe thread on both ends.
3. 2-inch PVC ball valve with 2-inch female pipe thread on both ends.
4. 2-inch PVC male 433-020 adapter with 2-inch male pipe thread on one end and 2-inch spigot (slip fit) on other end.
5. 2-inch 672-7180 manifold with 2-inch slip fit inlet and six 3/4-inch ribbed-barb outlets.
6. PVC primer and PVC glue.
7. Reservoir (barrel) for collecting water. 

1. First, add an extension to a downspout from your house or garage to direct the runoff into a reservoir such as a barrel, large plastic water tank or stock tank – the larger the volume, the better. Or cut off a downspout so that you can fit your reservoir under it.

2. Now it’s time to make fast-flowing soaker hoses. Drill holes (about 1/16 of an inch in diameter should be sufficient) in lengths of old garden hoses and use screw-on caps to plug the ends of the hoses that will not be connected to the barrel. Alternatively, fold over and crimp the end of a cut length of hose and secure it with a hose clamp, a couple of heavy-duty staples, some scrap wire or a pop-rivet. (Note: This setup may not have enough water pressure to work with the kind of porous soaker hoses often sold in garden stores.)

3. Next, head to your local hardware store. Take a sketch to show them what you want to do (see the illustration on Page XX), and have them help you find everything you need: a bulkhead fitting (at least 2 inches in diameter) to let water flow out of a hole you’ll drill (or cut with a hole saw) in your reservoir, plus a number of PVC fittings and a section of PVC pipe to build a manifold with multiple outlets for attaching hoses to the reservoir through the bulkhead. If you would rather just order the parts for our manifold online, we’ve included a source and part numbers below.