Rain barrels offer an effective method to conserve water by collecting rainfall from a roof for non-drinking uses like gardening or landscape irrigation. This harvested water is often free of chlorine, making it beneficial for plants. However, because the water is collected from roof surfaces, it can contain debris and contaminants, requiring careful management to prevent stagnation and biological growth. Maintaining a clean rain barrel ensures the water remains safe for its intended applications.
Initial Screening and Filtration
Keeping rain barrel water clean begins with installing fine mesh screens to stop large debris from entering the system. Screens should cover both the water inlet, which connects to a downspout, and any overflow points. A mesh with an aperture of less than one millimeter (0.955 mm is common) effectively keeps out leaves, shingle grit, and insects.
In addition to screening the barrel itself, proactive maintenance of the entire catchment area is necessary. Gutters should be cleaned regularly to prevent the buildup of leaves and organic material, which can break down and contaminate the collected water. Installing a leaf-eater, which is a specialized screen that deflects debris before it enters the downspout, can significantly reduce the organic load on the system.
A first-flush diverter can be integrated into the downspout system. This device automatically redirects the initial volume of rainwater, which contains the highest concentration of dust, bird droppings, and accumulated pollutants, away from the storage barrel. Once the diverter chamber is full, cleaner water is then directed into the rain barrel.
Controlling Pests and Biological Growth
Once water is inside the barrel, the focus shifts to preventing the growth of organisms, primarily mosquitoes and algae. Mosquitoes breed in standing water, so all openings, including the inlet and overflow, must be securely covered with fine mesh screening to deny adult access for egg-laying.
A method for controlling mosquito larvae is the use of products containing Bacillus thuringiensis israelensis (Bti). Bti is a naturally occurring bacterium that, when ingested by mosquito larvae, releases a protein toxin that prevents them from feeding, killing them before they mature into flying adults. This larvicide is safe for humans, pets, and plants, and is often available in a briquette or “dunk” form.
To inhibit algae growth, the rain barrel material should be opaque, or the barrel can be painted a dark color to block light penetration. Chemical sanitation is an option for reducing bacteria and mold, particularly if the water will be used on food crops. About one ounce of unscented household bleach can be added monthly for a typical 55-gallon barrel. The water should not be used for at least 24 hours afterward to allow the chlorine to dissipate.
Routine Cleaning and Maintenance Schedule
Regularly using the collected rainwater prevents long-term stagnation and maintains water quality. The barrel should be emptied frequently to ensure space for the next rainfall and eliminate standing water that could serve as a breeding ground for pests. Water that sits for extended periods is more likely to accumulate sediment and develop biofilm on the interior surfaces.
Deep cleaning of the rain barrel is recommended at least twice a year, or seasonally, to remove sediment and biological residue. This process involves completely draining the barrel and scrubbing the interior walls with a long-handled brush. A mild, non-toxic cleaning solution, such as diluted white vinegar or a mixture of baking soda and water, is effective for dislodging biofilm and algae.
Seasonal maintenance protects the barrel from physical damage caused by freezing temperatures. Before the first hard frost, the rain barrel must be completely drained and disconnected from the downspout to prevent cracking. The barrel should then be stored upside down in a sheltered location until spring, ensuring the system is ready for reconnection.