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 can be made compatible with centralized water supply by
tapping it using an electropump.
Calculating rainwater collection
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