Designing for Rain Barrel Success

To encourage frequent use, identify a location for your rain barrel that is as close to landscaped beds and container plants as possible.

To encourage frequent use, identify a location for your rain barrel that is as close to landscaped beds and container plants as possible.
Image courtesy: Clemson Extension Carolina Clear Program

Rain barrels are a form of small-scale rainwater harvesting for collecting and storing rainwater that runs off roof surfaces. The stored water is useful for irrigation in landscaped beds and container plants, creating wildlife features such as birdbaths or butterfly puddling areas, washing off equipment, and more. Rain barrels capture and use rainwater for non-potable applications. The following guidelines can help to ensure rain barrel projects are successful.

Select an appropriate location for your rain barrel; start by identifying how you plan to use the water. The rain barrel should not sit full, or the water will become stagnant, and water quality will decline. To encourage frequent use, place the rain barrel as close as possible to landscaped beds, container plants, birdbaths, and other areas you plan to irrigate with the rainwater.

To encourage frequent use, identify a location for your rain barrel that is as close to landscaped beds and container plants as possible.

This rain barrel is elevated on a wooden stand; cinder blocks or pavers may also be used. Rain barrels are typically elevated 12 to 36 inches to increase water pressure. In this system, metal strapping is used to provide additional stabilization since the rain barrel is located in an outdoor classroom space.
Kim Morganello, ©2023 Water Resources Associate Carolina Clear Coordinator

Use a measuring tape to determine the appropriate amount of roof surface area (in square feet) to direct toward your rain barrel. Multiply the surface area by 0.623 to calculate how many gallons of water flow off your roof in a one-inch rainfall. If using a single rain barrel, as little as 100 square feet of roof surface area may yield enough rainwater runoff to fill the rain barrel quickly.

Decide how to direct water from the roof into the barrel; options include gutters, a downspout, a rain chain, or simple sheet flow. If your home has gutters, select one downspout so that only a portion of the roof drains into the rain barrel. If your home does not have gutters, make observations during a moderate rain to determine where water flows off the roof in a concentrated fashion. A rain barrel can be placed strategically under roof corners and eaves to capture rainwater.

A properly designed rain barrel is critical. The point where water enters the rain barrel, usually the top, must be screened to prevent mosquito breeding and restrict debris such as leaves, twigs, and small animals from entering the barrel. Clean the screened top or entryway regularly. It is very important to fasten the lid securely as a safety precaution. Other key features include:

  • A spigot to turn the flow on and off.
  • An emergency overflow, which allows water to escape when the barrel is full and helps direct water overflow away from the building foundation.
  • A dark color rain barrel will prevent sunlight penetration and algal growth.

Design the system so that the stored water is easy to use and move. Elevate the rain barrel to increase water pressure by using the force of gravity to push water out of the barrel. Typically, rain barrels are elevated 12 to 36 inches above the ground. This creates enough pressure to move water through a spigot to fill a watering can or hose or use drip irrigation. For every 1 foot of elevation, you gain approximately 0.4 pounds of pressure (PSI). A raised barrel also allows easier access to the spigot, which can be beneficial when filling a watering can. Elevate a rain barrel by creating a cinder block or paver base or building a platform that raises the barrel off the ground. A 55-gallon rain barrel weighs over 450 pounds when full; you must properly secure elevated rain barrels to prevent injury.

To learn more about rainwater harvesting, reference the Clemson Extension HGIC 1728, Best Practices for Application of Harvested Rainwater on Edibles and HGIC 1729, Rainwater Harvesting Systems Guidance for Schoolyard Applications. Also, download a free copy of the Rainwater Harvesting for Homeowners Guide.

If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988.

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