Rain barrels are containers or systems which collect and store rain water from rooftops for later use, providing valuable and useful opportunities for water conservation while also preventing the loss of "stormwater" as runoff, which is frequently channeled into nearby streams and rivers, carrying pollutants and other contaminants into neighboring ecosystems and on to the Chesapeake Bay.

Inexpensive rain barrels can be made from food grade plastic barrels or heavy-duty trash cans, often for as little as 15 dollars, or they can be purchased pre-made from numerous nonprofit agencies, commercial manufacturers and retailers, in prices ranging from 25 to 150 dollars. 

Rain barrels can be used individually or linked in tandem to capture a greater volume of water.  They can be tapped to fill a watering can for watering hanging baskets and other plants, or used as the central water source for water-saving drip irrigation systems.

Rain Barrel Assembly Instructions
At long last, we've pulled together the assembly instructions (with a parts list) for the rain barrels offered through DEP's "Make & Take" workshops, including the recent Green Matters Symposium at Brookside Gardens.  The parts used in our design are all readily available at most home improvement centers and hardware stores -- except for the barrel.  We're still working on locating a free or inexpensive public source for refurbished, food grade barrels.  With the instructions above, and a barrel, anyone can assemble a large capacity rain barrel for as little as $15.

Maintaining Your Rain Barrel
A concise and handy guide for rain barrel maintenance developed by Pennsylvania's Nine Mile Run Rain Barrel Initiative.  Click above to download the brochure.

Arlington Echo - Revised Rain Barrel Assembly Plans [PDF]
Like many of us in the DIY (Do-It-Yourself) rain barrel business, the Outdoor Education Staff at the Arlington Echo Outdoor Education Center in Anne Arundel County are constantly tweaking, simplifying, and improving their approach and plans for rain barrel construction.  Click above to download the latest word on rain barrel wizardry, developed from the Maryland Association for Environmental and Outdoor Education Conference in 2005.  Thanks to Stephen Barry and Will Williams for their ongoing work.

Montgomery County "Make & Take Workshops"
During the past several years, the Montgomery County Department of Environmental Protection has conducted a series of free "Make-and-Take" Rain Barrel Workshops for county residents (and others) through the financial support of the Chesapeake Bay Trust and in cooperation with the Outdoor Education Association, Smith Center for Environmental Education, the Izaak Walton League - Wildlife Achievement Chapter, and the Greater Sandy Spring Green Space Conservancy.  Learn more about upcoming workshops on our Rainscapes Calendar of Events page, or be notified by eSubscribing for our Rainscapes Gazette electronic newsletter.  Click here for details.

General Information:

• King County Dept of Natural Resources:

• Harvesting Rainwater for Landscape Use by P. Waterfall, Arizona Cooperative Extension

• Rainwater Harvesting by Daniel Winterbottom (Landscape Architecture, April 2000).

Designs and Assembly Instructions

• Arlington Echo Outdoor Education Center:
  The nonprofit Center also offer barrels for sale and hands-on workshops

• King County, Washington

• How to Build and Install a Rain Barrel [pdf]
  Center for Watershed Protection

• Build a Simple Rain Barrel
  Maryland DNR - Green Building Program

Downspout Connections

There are a number of creative methods for directing rainwater from your downspout to your rain barrel or rain barrel system.  Typically, most homeowners and installers use a flexible downspout elbow made from plastic.  This approach simply relocates your downspout water into the rain barrel, with surplus water carried away by an overflow hose, or spilling over the top of the barrel during a heavy downpour.  While a workable solution, it is best to employ a flexible connector only for smaller drainage areas (small sections of rooftop), as the runoff from larger areas will easily overwhelm one or more typical barrels.  Keep in mind that a typical rainstorm falling on a 20x50 foot roof surface will provide 600 gallons of water -- enough to fill about ten rain barrels!  See below.

Fortunately, there have been a number of innovations which help rain barrel users divert only as much rain water as their barrel or barrels can hold, while allowing the remainder, often the majority of the flow, to drain through the existing downspout and off to a desired location away from the adjacent building.

These diverters fall into two basic categories.  The simplest, pictured at right, simply uses a flip-down "tongue" which either channels water into the rain barrel, or can be flipped up to redirect the flow of water through the existing downspout.  The obvious shortcoming is that someone will have to actually "activate" the unit, going out in the rain to either engage the diverter or to deactivate it.  The Save the Rain Diverter shown currently retails for $16.95 for one unit; $14.95 for two or more units.  Click on the image or link above for more information*.

Another approach, which generally costs approximately ten dollars more per unit, allows you to divert a smaller percentage of your overall downspout flow and utilizes an automatic backflow or back pressure system which will stop diverting water to the barrel after it is filled.  Excess water will continue flowing through your downspout system.

These units typically include a flexible hose which connects the diverter to your rain barrel, which permits you to position your rain barrel in a location other than directly below your downspout.  Several models are available, including the GWS Diverter Kit for $22.95, shown at top, or the Gardeners Supply Company Downspout Diverter for 24.95, shown at right.  For more information on either unit, click on the image or the green-highlighted product name*.

Rain Barrels: Capacity and Sizing

Sizing of Rain Barrels
The required capacity of a rain barrel is a function of the rooftop surface area that drains to it, the inches of rainfall required to fill the barrel, and water losses, due mainly to evaporation.  A general rule of thumb to utilize in the sizing of rain barrels is that 1 inch of rainfall on a 1000 square foot roof will yield approximately 600 gallons. From the Low Impact Development Center.  To calculate the amount of runoff from your rooftop use the precise formula provided below, or simply multiply the square footage of your roof by 625 and divide by 1000.

Developed from the Texas Water Development Board-Rainwater Harvesting Web Page