A downspout diverter, also known as a downspout adapter, is an optional component of a building’s gutter and downspout system. It allows greater control over the direction of rainwater flow. Most often, a downspout diverter is used as part of a rainwater catchment system to redirect water flow into a catchment container before it exits the downspout’s outlet. Simple downspout diverters direct water into the container until it is full, at which point the overflow backs up into the downspout and continues out the regular downspout outlet to the ground or a drain. A downspout diverter might include an on/off feature that allows the user to redirect the water flow manually.
Rainwater catchment systems range from simple, affordable, do-it-yourself setups to more complicated, expensive whole-building systems. Regardless of its complexity, a properly designed system can collect more than 250 gallons (946 liters) of water per 500 square feet (46.45 square meters) of collection surface for every inch (2.54 centimeters) of rain that falls. For some people, such as most home gardening enthusiasts, rainwater harvesting is more of a hobby. For others, such as those in regions prone to drought, it is a necessity.
In its simplest form, a rainwater catchment system consists of three main components: gutters and downspouts; a catchment container, such as a 55-gallon (208-liter) barrel or a cistern; and a means of distribution, such as a hose, spigot or, in whole-building systems, a pump system. As rainwater sheds from the building’s roof, the gutters and downspouts collect and direct the flow of rainwater from the roof into a catchment container.
When the setting allows for it, the catchment container is positioned immediately beneath the downspout outlet, allowing the free flow of rainwater into the container. In cases where the terrain makes such positioning difficult or impossible, a downspout diverter is attached to the downspout to direct the water to a nearby container. The downspout diverter might be a "Y" design to which additional lengths of downspout attach sufficiently to reach the catchment container. Other downspout diverter designs include rectangular or round downspout diverters that install in line with the downspout pipe and connect to the catchment container via a length of flexible polyvinyl chloride (PVC) hose.
Rainwater contains both chemical and environmental contaminants from roofing materials, animal waste, environmental pollution and even the gutter and downspout materials and adhesives. Collected rainwater is fine for watering gardens, flushing toilets during a power outage or other non-potable uses. Untreated rainwater is not safe for drinking, cooking or bathing by humans or animals.
Common methods of sterilization, such as boiling or adding bleach to the water, might effectively treat organic contaminants, but these methods will do nothing to remove chemical contaminants such as heavy metals. There are filtration systems that are capable of treating organic and chemical contaminants, making the water suitable for potable uses. These filtration systems, however, generally are expensive relative to the cost of the water catchment system and typically are installed only by those with whole-building water catchment systems.