Collection Surfaces (Roofs, Solar Panels, Collection Surfaces)
Rainwater can be harvested using roofs, solar panels, and other aboveground surfaces, and is carried by gutters, downspouts or pipes to storage vessels. The components should be made of materials that do not corrode or leach toxins, or adversely affect taste or odor, especially if intended for potable use or irrigating food crops. Collection surfaces should be kept as clean as possible.
Conveyance System (Gutters, Screens, Downspouts)
The roof catchment is connected with a gutter and down-pipe system, with diverters, gutter guards and filtration, to deliver rainwater to the storage tank. Wire meshes or inlet filters should be placed over the top of gutters and/or down-pipes to prevent leaves and other debris from entering storages. These meshes and filters should be cleaned regularly to prevent clogging.
First Flush Diverters
First-flush devices ensure a certain degree of water quality in harvested rainwater. The first five gallons of runoff from a gutter, roof or other surface is likely to contain various impurities such as bird droppings and dust. A first-flush device prevents this initial flow from draining into the storage tank. If diverters are not available, a detachable down-pipe can be used manually to provide the same result.
Filtration and Treatment Systems
The degree and type treatment will be determined by the intended end use of your rainwater. Irrigation may require none at all. But, for potable or other critical uses, you will need a rigorous filtration and treatment system that removes chemical and biological contaminants coming from the atmosphere and collection surfaces. Check suppliers’ websites, as technology continues to evolve.
Storage can be aboveground or underground, and consists of barrels, tanks, cisterns, or bladders, starting at the 50 gallon size. They must be opaque (to avoid algae growth) and sealed (to prevent access by children, animals and mosquitoes). Storages should preferably be fitted with a mechanism such as a tap or outlet pipe that enables hygienic abstraction of water. Materials include steel, polyethylene and concrete. For potable water use, more rigorous specifications apply.
The components of the distribution system are determined by the location and end use of the water. Storage located higher than the end use may allow for a simple gravity-fed pipe system. Otherwise, pumps will be needed. Valves, monitors and timers are part of an efficient irrigation system. If there are any connections to plumbing served by municipal potable water systems, approved backflow prevention devices are necessary.