The rooftop surface should be made of relatively smooth material with good drainage, either from a sloped roof or an efficient roof drain system. Some materials may leach chemicals making the water less desirable for watering food gardens, providing drinking water to pets, and/or for any purposes that involve significant body contact.

The collection and conveyance system consist of gutters, downspouts, and diverter systems that channel stormwater runoff into the rain barrel. Gutters and downspouts should be kept clean and free of debris and rust.

Pre-screening of water before it enters the rain barrel is required to keep sediment, leaves, contaminants, and other debris from the system. Leaf screens and gutter guards meet the minimal requirement for pre-screening of typical rain barrels. The purpose of pre-screening is to significantly cut down on maintenance of the rain barrel itself by preventing debris and organic buildup and thereby decreasing bacterial growth in the rain barrel.

The rain barrel is the most important and typically the most expensive component of a rainwater harvesting system. Typical rain barrels hold approximately 50 gallons. RainSmart Rebates rain barrel projects must be sized to capture at least 50 gallons. Multiple rain barrels can be placed together and connected with pipes to balance water levels and increase overall storage, as needed.

Rain barrels should be placed on a solid foundation of stone or wood and elevated 6 to 18 inches off the ground. The load-bearing capacity of the soil must be considered since full rain barrels can be very heavy. A full 50-gallon rain barrel will weigh approximately 400 pounds. Additional factors to consider when designing a rain barrel collection system include:

• Rain barrels should be UV-light and impact resistant.
• Rain barrels may be purchased ready-made or constructed using food grade plastic barrels.
• Rain barrels should be opaque or otherwise protected from direct sunlight to inhibit algae growth.
• Rain barrels that have an open top should utilize two layers of window screens secured to the top to prevent mosquitos from getting in and to keep leaves and debris out.

To size a rain barrel(s), you must plan for water quality improvement. A 1-inch rainfall event is a typical recommended amount to capture in a rainwater harvesting tank.

Given that most rain barrels hold approximately 50 gallons, capturing a full 1-inch of runoff at a downspout will require connecting multiple barrels together or using a larger tank. Most homeowner systems that use only one rain barrel are significantly undersized for a 1-inch storm. This is not a problem, but you will need to carefully consider the overflow component.

The overflow at the top of the rain barrel must carry extra water away from the rain barrel and about 10 feet away from any adjacent buildings once the tank fills up. The diameter of the overflow outlet pipe should be adequate to carry overflow water without the rain barrel overtopping, typically 1 to 3 inches for a residential system. Place a screen over the end of the overflow pipe to prevent rodents and insects from getting into the rain barrel. If possible, lead the overflow pipe to a rain garden, or other area that will allow water to infiltrate into the ground.

For simple gravity-fed rain barrel systems, place an outlet spigot near the bottom of the rain barrel. A regular hose-bib spigot is the easiest type of outlet to use because a garden hose or soaker hose can be directly attached. Keep the spigot closed to collect and store rainwater for later use. It is important to remember to monitor the level of rainwater within the barrel, especially during the spring months when there may be frequent rain events that could lead to the barrel overflowing. As with the overflow pipe, drain the outlet/hose to a nearby rain garden, lawn or other location where the water can soak into the ground.

Level the ground where the rain barrel will be located using rakes or shovels. Test soil compaction by stomping on it or chopping into it. Tamp it down and build a foundation or base using gravel, wood, block or pavers. Foundations raise the elevations of the rain barrels, and clearance under the downspouts should be re-measured to know where to cut off the downspouts.

Measure the height of the rain barrel and make sure there is enough clearance to get the rain barrel under the downspout connection point. Don’t forget to account for the height of the foundation below the rain barrel.

Assemble the rain barrel and any necessary connection hardware. Pre-built kits may have this step partially or fully completed. Otherwise, cut a hole in the lid if necessary, and affix the screen to the lid. Alternatively, connect the downspouts to another screening device or first flush diverter. Install a hose bib 6 inches from the bottom of the rain barrel if there isn’t one already. Attach additional hardware as necessary if the system will have multiple rain barrels or a dedicated overflow hose. An interconnecting hose between rain barrels will equalize the water level in the rain barrels if the water level is above this bridge. An overflow outlet point should be installed near the top, leaving at least 2-6 inches from the top of the rain barrel for the air gap.

Put the rain barrel in place on the foundation and confirm that it is stable and level. Route the downspout into the top of the rain barrel. This will likely involve cutting off a section of the downspout with a hacksaw and attaching a curved downspout section to lead the downspout into the rain barrel inlet. Connect any filtration or diversion devices to the downspout, if applicable.