What is a Rain Barrel ?

A Rain Barrel is a water tank which is used to collect and store rain water runoff, typically from rooftops via rain gutters. Rain Barrels are devices for collecting and maintaining harvested rain.

Rain Barrels are installed to make use of soft rain water for home use, reduce public utility water use, and aid self-sufficiency. In arid climates, rain barrels are often used to store water during the rainy season for use during dryer periods. Rain Barrels can also be used for retention of storm water for release at later time.

Rain water can be used for flushing toilets, in washing machines, watering gardens, washing cars, agriculture, and sometimes for drinking, if special care and proper filtration is preformed so that the water is not contaminated.

Disadvantages of a Rain Barrel used for drinking water include the initial upfront cost, especially where water charges are otherwise fixed. Occasional maintenance to the barrel is also required, or the user runs a health risk if maintenance is not carried out.^[1] However, many homes use small scale rain barrels to harvest small quantities of water for landscaping/gardening applications rather than a potable water use. These small rain barrels, often recycled from food storage and transport barrels or, in some cases, whiskey and wine aging barrels, are often inexpensive.

Widespread use of Rain Barrels also changes the amount of rainwater reaching the ground in a particular area and draining into streams. Depending on the climate, this either helps prevent erosion, sedimentation, and/or pollution, and can reduce the strain on stormwater drainage systems; or it could cause rivers to dry up and ponds to stagnate if the water is diverted to a different watershed. If collected water is used in the same watershed in which it is collected, rainwater collection actually can stabilize flow in rivers and provide more regular and filtered groundwater transfer into ponds.

Contamination and maintenance

If Rain Barrel water is used for drinking, it must be filtered first. Filtration (such as reverse osmosis or ultra filtration) may remove pathogens which may be present in rainwater (such as cryptosporidium and giardia), or for chemical contamination in some areas. While rain water does not contain chlorine, contamination from airborne pollutants, which settles onto rooftops, may be a risk in urban or industrial areas. Many water suppliers and health authorities, do not advise using rainwater for drinking when there is an alternative mains water supply available. However, reports of illness associated with rainwater tanks are relatively infrequent, and public health studies in South Australia (the Australian state with the highest rainwater usage rate) have not identified a correlation. Rainwater is generally considered fit to drink if it smells, tastes and looks fine^[2]; However some pathogens, chemical contamination and suspended metal may produce neither smell, taste and not be visible to the eye.

Certain paints and roofing materials which may cause contamination. In particular, a Melbourne Water publication advises that lead-based paints never be used. Tar-based coatings are also not recommended, as they affect the taste of the water. Zinc can also be a source of contamination in some paints, as well as galvanised iron or zincalume roofs, particularly when new, should not collect water for potable use. Roofs painted with acrylic paints may have detergents and other chemicals dissolve in the runoff. Runoff from fibrous cement roofs should be discarded for an entire winter, due to leaching of lime. Chemically treated timbers and lead flashing should not be used in roof catchments. Likewise, rainwater should not be collected from parts of the roof incorporating flues from wood burners. Overflows or discharge pipes from roof-mounted appliances such as air-conditioners or hot-water systems should not have their discharge feed into a rainwater tank.

Maintenance includes checking roofs and rain gutters for vegetation and debris, maintaining screens around the tank, and occasionally desludging (removing sediment by draining and cleaning the tank of algae and other contaminants).

Rainwater tanks which are not properly sealed (secured at the top) may act as breeding grounds for mosquitoes.^[3]

Water supply augmentation

In some cities, installation of Rain Barrel may be mandatory, or may help a new building be approved. For example, in Victoria, Australia new houses which have rainwater tank connected to all flush toilets are given an additional 1-star of the required 5-star House Energy Rating. Some US governments such as The City of Austin, Texas subsidize purchases of rainwater tanks or provide rebates in areas where they are considered an important means of water supply augmentation.

Rainwater to supplement drinking water supplies may be seen as an alternative to other water supply options, such as recycling or seawater desalination. Tanks are often perceived to have environmental costs that are comparatively lower than other water supply augmentation options. Where storm water feeds natural creeks and streams, there are concerns about rainwater harvesting systems reducing the amount of run-off entering natural bodies of water.

Rainwater collection from roofs can be calculated using the following formulas:

  1 inch of rain on a 1000 square feet roof yields 623 gallons of water