Rainwater tank

There are also many low cost designs that use locally available materials and village level technologies for applications in developing countries where there are limited alternatives for potable drinking water.

[3] While rain water does not contain chlorine, contamination from airborne pollutants, which settle onto rooftops, may be a risk in urban or industrial areas.

[citation needed] Australian standards may differ greatly from other places in the world where rainwater is commonly used for drinking water.

In the semi-arid western state of New Mexico, for instance, many residents in the Taos and Santa Fe areas in particular use rainwater either for landscaping purposes or even all household uses (including potable indoor water).

Most people who are rainwater users for potable purposes in the US make certain that their water is safe through filtration, ultraviolet sterilization, and testing.

Zinc can also be a source of contamination in some paints, as well as galvanized iron[5] or zincalume roofs, particularly when new, should not collect water for potable use.

While the plastic tank is an inert container, the collected acid rain could and should be analysed and pH adjusted before being brought into a domestic water supply system.

Full tanks are usually installed above ground, and are usually opaque to prevent the exposure of stored water to sunlight, to decrease algal bloom.

Companies recommend a 1,135 litres (300 US gal) tank for a house supporting two people (if compost toilets are placed) and if the region receives at least 762 mm (30.0 in) of precipitation a year.

Most rainwater catchment tanks used throughout the world are composed of virgin polyethylene, a substance which in the US is both FDA and NSF approved for potable water storage.

Polyethylene tanks, when placed above ground, can be subject to algae growth as well as the possibility of a short life (about 20 years) due to normal UV exposure in sunlight.

These came as an evolution of a geosynthetic applications called Infiltration Tanks, which when stacked provide a void space volume which allows for the storing of water.

In Australia, the brand TransTank International manufactures portable water tanks from specially formulated polyethylene for transport and static applications.

Some governments subsidise purchases of rainwater tanks or provide rebates in areas where they are considered an important means of water supply augmentation.

[10] In the United States, Santa Fe County, New Mexico requires a rainwater collection system on all new construction with greater than 2,500 square feet (230 m2), mostly for landscaping purposes and to prevent over-reliance on wells but in some instances because ground water is prohibitively expensive to obtain, if even available.

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.

In 2009, legislation in Colorado was enacted that permits capture of rain water for residential use subject to strong limitations and conditions.

Rainwater Hog modular tanks invented by Sally Dominguez to fit within building structure were used in the Modabode House of the Future floor and on the foyer wall of the Department of Sustainability building in Anglesea, Victoria, harnessing the higher value of the stored rainwater to add effective thermal mass to the enclosed spaces.

A house in Cape Schanck, Victoria, Australia, uses an internal rainwater tank to provide cooling to the living room in summer.