Rainwater collection is almost as old as civilization itself. Ancient peoples collected rainwater from natural rock catchments using pots, woven baskets, and pools, and it wasn't long before man-made collection systems for drinking and agricultural purposes developed. You can make use of this technology for your garden by building a simple rain barrel to harvest runoff from your gutters.
In wetter climates, rainwater collection can significantly offset and even replace conventional water sources in your garden, and in dryer areas a rain barrel still lowers your water bill and reduces your water usage.
Basic Rain Barrel Components
At its most basic, a rain barrel is any container that collects rainwater. A bucket shoved under a downspout will collect water during a rainstorm. Ideally, your rain barrel should be a little more advanced than the bucket system. Open rain barrels allow dirt, sunlight, and mosquitos into your rain barrel. Dirt clogs your faucet and contaminates your water. Sunlight encourages algae to grow, similarly clogging your barrel and contaminating water. Worst of all are the mosquitos. Nobody wants to breed a mosquito swarm in their backyard.
The three basic components of a rain barrel are 1) a way for water to enter the barrel, 2) an overflow component, and 3) a faucet. Most of these designs also require a drill, caulk, and a few pieces of hardware from the store.
Laundry Detergent Rain Jug
Most of us own a small rain barrel without realizing it. Large laundry detergent jugs already come with a little spigot (where the detergent comes out) and an overflow valve (the cap). All you need to do is cut a hole in the top for the downspout, like this Reader's Digest article illustrates, and you have a mini rain barrel for your garden. This is a good solution for rental properties where altering your downspout might irritate your landlord.
Super Simple Rain Barrel
This is by far the simplest rain barrel design out there. It is also not quite as effective as some of the larger systems. For this design, you will need a 55-gallon plastic barrel (or another large storage tank), a faucet and a corresponding drill bit (depending on the size of your faucet), and a piece of screen.
Drill a hole near the bottom of your barrel for the faucet and a hole near the top for your overflow valve, sized appropriately. There are rain barrel kits available online and in stores that supply you with these parts at affordable prices. (Your overflow valve can also consist of a small hole covered with a piece of screen to prevent mosquitos from entering.)
Place your barrel on a row of cinder blocks or other slightly raised surface beneath your gutter. You may have to cut out a section of your drain pipe to allow this. Cut a hole in the barrel beneath the pipe and place your screen over the hole to block debris. While you could copy the design of a commercial barrel, the smaller the screened hole, the less sunlight enters the barrel and the less chance algae has to form.
Closed Rain Barrel
There is a way to avoid algae formation and mosquito population completely - a closed rain barrel system. This rain barrel design is similar to number 2, but instead of putting a screen beneath the pipe you will need to fit the pipe with an adapter to go directly into your barrel like this one carried by Home Depot. This adapter also has a built in overflow valve, eliminating the need to drill your own hole. All you need is a faucet and your barrel is ready to collect water for you.
Most DIY rain barrel designs call for 55-gallon barrels, due to their easy availability and affordability. Many of these systems work just as well with an IBC (intermediate bulk container) tote. These containers can be found on craigslist or from a factory for only a few dollars more than a 55-gallon barrel. The benefits of an IBC tote are substantial. They already have a hole in the top for your downspout and a spigot installed, and they hold a lot more water. As with a barrel, always make sure no harmful chemicals were stored in the container and clean it out well before use.
IBC totes do not come with overflow valves, so you will need to install one or else your downspout could back up and damage your gutters. The central location of the hole also requires an adapter to direct water from your downspout to your tote.
Multiple Rain Barrel System
Why settle for one rain barrel when you could have an infinite number? This video is an excellent example of a multiple, closed rain barrel system using PVC piping and 55-gallon barrels.
There are countless variations of these DIY rain barrel designs. Now that you know the basics of rain barrel construction, don't be afraid to get creative and try something a little different as you plan out your rainwater collection system for your garden.