Weekly DIY: Rain Barrels

June 27, 2007

Photo Credit: Elizabeth Redmond

I've been wanting to put in a couple of rain barrels at my house this year. We put in some garden plants this weekend, and they are going to need to be watered. Rain barrels are great because they help conserve water and cut down the amount of potable water that needs to be used. Rain barrels are commercially available for around $100 (or more). These are more "decorative" (if you find a piece of plastic molded with a wood barrel pattern decorative), but with a drill, some silicone sealant, and a couple of basic parts, you can build a rain barrel of your own.

It is important to remember that this is not drinking water that you are collecting. Without further treatment, there are too many possible problems, from dust and dirt to chemicals (from roof materials) to microorganisms that may colonize an available water supply. There are rainwater catchment systems that are designed for potable water use. These are more involved, and need to have other elements in the system beyond what is being discussed here.

It is also important to make sure to prevent the standing water from becoming a mosquito breeding facility, either by closing the barrel with a screen (like a window screen) or by using mosquito dunks (a time release tablet that contains a bacterial agent that kills mosquito larvae, but do not affect people, fish, animals or plants).

Rain barrels can collect a surprisingly large amount of water. "For every 1000 square feet of roof space being used to capture rain you can expect to catch around 600 gallons from one inch of rain fall (at a theoretical 100% catch rate). Some larger roofs can easily be 2000+ square feet." (The Sietch) Conversely, if you have a 100 square foot garden, you can figure that you will want to supply 60 gallons of water for every inch of rainfall you are trying to make up. So if you collect and use five 55-gallon barrels of rainwater, that's approximately 5" of additional effective rainfall that you've supplied to your garden. With a typical 55-gallon barrel size, you are only likely to capture a fraction of the total water that falls on your roof. But this could be increased by putting barrels at several corners, to capture the rainfall at multiple downspouts.

Photo Credit: Elizabeth RedmondBuilding the barrel is mostly a matter of cutting plastic. Using a wide bore drill bit or a hole saw is the best way to cut the plastic. A good silicone sealant for submerged use can seal the spigot installation if it leaks excessively.

You need to install a hole in the lid as an inlet for the water coming from the downspout, a hole in the side with a valve, near the bottom, so that you can drain the water out when you are ready to water your plants, and a hole near the top, for an overflow, to control the water if the barrel gets completely full.

The following instructions are taken from the Center for Watershed Protection directions:

STEP 1. Cut Holes in Barrel

  • Cut lower drain hole

Measure about 1 inch above the bottom of the barrel where the barrel side begins to rise toward the top. Using a 3/4" bit (or hole saw), drill a hole through the barrel.

  • Cut upper drain hole

Mark the upper drain hole according to where you want the overflow to be located in relationship to the lower drain. Use a 1-5/8" hole saw to cut out the overflow hole.

  • Cut top hole for atrium grate (filter)

Using the atrium grate as a template for size, mark a circle at the center of the top of the drum (locating the rainwater inlet in the center of the barrel lets you pivot the barrel without moving the downspout). Drill a 1/2" hole inside of the marked circle. Use a router, jigsaw or coping saw to cut until the hole is large enough to accommodate the atrium grate, which filters out large debris. Don’t make the hole too big – you want the flange of the atrium grate to fit securely on the top of the barrel without falling in.

  • Cut notch to hold hose

Using a 1/2" bit or hole saw, cut out a notch at the top of the barrel rim (aligned so that it is above the lower drain hole). The notch should be large enough so that the end of the hose with the adapter will firmly snap into place.

STEP 2. Set Up Barrel and Modify Downspout

  • Set up barrel

Since water will only flow from the garden hose when the hose is below the barrel, place the barrel on high ground or up on cinder blocks or a sturdy wooden crate underneath your downspout.

  • Modify your downspout

Cut your existing downspout using a saw so that the end can be placed over the top of your rain barrel. Use a 3” vinyl downspout elbow to connect the two downspout pieces (or use a downspout adapter and a piece of corrugated plastic pipe). Trim the end of the downspout if necessary.

STEP 3. Assemble Parts

  • Attach garden hose to lower drain hole

Screw in the 1/2" PVC male adapter to the lower drain hole. The hard PVC threads cut matching grooves into the soft plastic of the barrel. Unscrew the 1/2" PVC male adapter from the hole. Wrap threads tightly with teflon tape (optional). Coat the threads of the coupler with waterproof sealant (optional). Screw the coated adapter back into the hole and let it sit and dry for 24 hours (optional). Attach 5’ foot garden hose to the PVC male adapter. Attach the 3/4" x 1/2" PVC male adapter to the other end of the hose (this can be readily adapted to fit a standard garden hose).

  • Attach drain hose to upper drain hole

Put the 1-1/4" male threaded coupling inside the barrel with the threads through the hole. From the outside, screw the 1-1/4" female barbed fitting onto the threaded coupling. Use silicone on the threads (optional). Attach 5’ section of drain hose to upper fitting.

  • Place atrium grate and screen in top hole

Using PVC glue, secure a piece of fine mesh window screen inside or outside of the atrium grate to filter out debris and control mosquitoes (optional). Place the atrium grate into the hole (basket down).

  • Position the downspout

Position the end of your downspout so it drains onto the atrium grate on the rain barrel.

Photo Credit: Elizabeth RedmondIt is possible to increase your storage capacity by connecting two (or even more) barrels together at the bottom, so that they fill up equally during a rainfall. Unless you are in an area subject to strong downpours, this is probably not a concern for most uses, and the water will evaporate faster if there is more surface area, as having the water in two half-full barrels instead of a single, full barrel.

Getting the barrels can take a little digging, but there are many sources for finding them. Rain barrels have been getting a lot of local attention recently, and I'm still waiting to get a barrel from my source. Some possible sources for free or inexpensive barrels include soda bottlers (syrup), car washes (soap), and food preparation facilities (bulk foods). The local water treatment plant here gets bulk loads of chemicals which they use for treating the water. The leftover 55-gallon plastic drums are then available to local residents for use as rain barrels. Bio-diesel enthusiasts are also looking to get the same barrels to store their stock, so the competition for these barrels is heating up. Our bio-diesel maven, Ryan Thibodaux, was very helpful
in pointing out some of these suggested sources for finding barrels. And Elizabeth Redmond provided the photos of her own rain barrel setup.

Further information:
Center for Watershed Protection
The Sietch
DIY Network