Rainwater tank - AbsoluteAstronomy.com

Some of the rainwater tanks around
CERES Community Environment Park

CERES Community Environment Park

The CERES Community Environment Park, or Centre for Education and Research in Environmental Strategies, is an award-winning urban environmental centre located in urban Brunswick East, Victoria, Australia...

,
in Melbourne, Australia.

A rainwater tank (sometimes called a rain barrel in North America, or a water butt in the UK) is a water tank

Water tank

A Water tank is a container for storing water. The need for a water tank is as old as civilized man, providing storage of water for drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemical manufacturing, food preparation as well as many...

used to collect and store rain water runoff

Surface runoff

Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

, typically from rooftops via rain gutter

Rain gutter

A rain gutter is a narrow channel, or trough, forming the component of a roof system which collects and diverts rainwater shed by the roof....

s. Rainwater tanks are devices for collecting and maintaining harvested rain

Rainwater harvesting

Rainwater harvesting is the accumulating and storing of rainwater for reuse before it reaches the aquifer. It has been used to provide drinking water, water for livestock, water for irrigation, as well as other typical uses. Rainwater collected from the roofs of houses and local institutions can...

.

Rainwater tanks are installed to make use of rain water for later use, reduce mains

Public utility

A public utility is an organization that maintains the infrastructure for a public service . Public utilities are subject to forms of public control and regulation ranging from local community-based groups to state-wide government monopolies...

water use for economic or environmental reasons, and aid self-sufficiency

Self-sufficiency

Self-sufficiency refers to the state of not requiring any outside aid, support, or interaction, for survival; it is therefore a type of personal or collective autonomy...

. Stored water may be used for watering garden

Garden

A garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form today is known as a residential garden, but the term garden has...

s, agriculture, flushing toilets

Flush toilet

A flush toilet is a toilet that disposes of human waste by using water to flush it through a drainpipe to another location. Flushing mechanisms are found more often on western toilets , but many squat toilets also are made for automated flushing...

, in washing machine

Washing machine

A washing machine is a machine designed to wash laundry, such as clothing, towels and sheets...

s, washing cars, and also for drinking

Drinking water

Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

, especially when other water supplies are unavailable, expensive, or of poor quality, and that adequate care is taken that the water is not contaminated or the water is adequately filtered.

In ground rainwater tanks can also be used for retention of stormwater

Stormwater

Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...

for release at a later time. In arid

Arid

A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

climates, rain barrels are often used to store water during the rainy season for use during dryer periods.

Rainwater tanks may have a high (perceived) initial cost. However, many homes use small scale rain barrels to harvest minute quantities of water for landscaping/gardening applications rather than as a potable water surrogate. These small rain barrels, often recycled from food storage and transport barrels or, in some cases, whiskey and wine aging barrels, are often inexpensive. 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. While most are properly engineered to screen out mosquito

Mosquito

Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es, the lack of proper filtering or closed loop systems may create breeding grounds for larvae. With tanks used for drinking water, the user runs a health risk if maintenance is not carried out.

Contamination and maintenance

If rainwater is used for drinking, it is often filtered first. Filtration (such as reverse osmosis

Reverse osmosis

Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...

or ultrafiltration

Ultrafiltration

Ultrafiltration is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained, while water and low molecular weight solutes pass through the membrane...

) may remove pathogens. While rain water is pure it may become contaminated during collection or by collection of particulate matter in the air as it falls. While rain water does not contain chlorine

Chlorination

Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...

, contamination from airborne pollutants

Air pollution

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

, which settles onto rooftops, may be a risk in urban or industrial areas. Many water suppliers and health authorities, such as the New South Wales Department of Health

New South Wales Department of Health

The New South Wales Department of Health, a department of the New South Wales Government, is responsibile for monitoring the performance of the public health system in New South Wales, particularly through public hospitals...

, 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

South Australia

South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...

(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; However some pathogens, chemical contamination and sub-micrometre suspended metal may produce neither smell, taste and not be visible to the eye.

Certain paints and roofing materials may cause contamination. In particular, a Melbourne Water

Melbourne Water

Melbourne Water is a government owned statutory authority that controls much of the water system in Melbourne, Victoria, Australia including the reservoirs, and thesewerage and drainage system that services the city.- Overview :...

publication advises that lead-based paints never be used. Tar

Tar

Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

-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 galvanized iron or zincalume roofs, particularly when new, should not collect water for potable use. Roofs painted with acrylic paint

Acrylic paint

Acrylic paint is fast drying paint containing pigment suspension in acrylic polymer emulsion. Acrylic paints can be diluted with water, but become water-resistant when dry...

s 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.

"Copper Poisoning," a 2010 news article, linked copper poisoning to plastic tanks. The article indicated that rainwater was collected and stored in plastic tanks and that the tank did nothing to mitigate the low pH. The water was then brought into homes by copper piping. The copper was released by the high acid rainwater and caused poisoning in humans. It is important to note that, 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. The solution is to monitor stored rainwater with swimming pool strips, cheap and available at swimming pool supply outlets.

If the water is too acidic, the state, county or local health officials may be contacted to obtain advice, precise solutions and pH limits, and guidelines as to what should be used to treat rainwater to be used as domestic drinking water.

Maintenance includes checking roofs and rain gutter

Rain gutter

A rain gutter is a narrow channel, or trough, forming the component of a roof system which collects and diverts rainwater shed by the roof....

s for vegetation

Vegetation

Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

and debris

Debris

Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...

, maintaining screens

Sieve

A sieve, or sifter, separates wanted elements from unwanted material using a woven screen such as a mesh or net. However, in cooking, especially with flour, a sifter is used to aerate the substance, among other things. A strainer is a type of sieve typically used to separate a solid from a liquid...

around the tank, and occasionally desludging (removing sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

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 mosquito

Mosquito

Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es.

Tanks

Rainwater tanks may be constructed from materials such as plastic (polyethylene

Polyethylene

Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

), concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, galvanized steel, as well as fiberglass

Fiberglass

Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...

and stainless steel

Stainless steel

In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

which are rust and chemical-resistant. Tanks are usually installed above ground, and are usually opaque

Opacity (optics)

Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...

to prevent the exposure of stored water to sunlight, to decrease algal bloom

Algal bloom

An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

.

Tanks may be covered

Seal (mechanical)

A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage , containing pressure, or excluding contamination...

and have screen inlets to exclude insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, debris

Debris

, animals and bird droppings. Almost all steel tanks currently produced for household rainwater collection come with a plastic inner lining to increase the life of the tank, prevent leaks and protect the water quality

Water quality

Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

.

Apart from rooftops, tanks may also be set up to collect rainwater from concrete patio

Patio

A patio is an outdoor space generally used for dining or recreation that adjoins a residence and is typically paved. It may refer to a roofless inner courtyard of the sort found in Spanish-style dwellings or a paved area between a residence and a garden....

s, driveway

Driveway

A driveway is a type of private road for local access to one or a small group of structures, and is owned and maintained by an individual or group....

s and other impervious surface

Impervious surface

Impervious surfaces are mainly artificial structures--such as pavements that are covered by impenetrable materials such as asphalt, concrete, brick, and stone--and rooftops...

s.

Initial sizes typically ranged in capacity from around 400 to 100,000 litres (100 to 25,000 US gallon

Gallon

The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...

s), today modern technology has allowed modular and scalable applications to go into sizes of millions of litres or hundreds of thousands of US gallon

Gallon

s.

Smaller tanks, such as the plastic 208-litre

Litre

pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...

(55-gallon barrel) are also used in some cases. Modern modular systems which are scalable, like the 51 gallon (193 litre) Rainwater HOG

Rainwater Hog

Rainwater HOG is a modular water storage tank which can be used horizontally or vertically for Rainwater Harvesting, emergency water storage and post-filter greywater storage...

module and the 500 litre (133 gallon) Stradco Aquabarrel can be used to decentralize the rainwater catchment by storing smaller volumes at each downspout. Larger tanks are commonly used where there is no access to a centralised water supply. Companies such as Solar Survival Architecture recommend a 300 gallon (1135 litre) tank for a house supporting 2 people (if compost toilets are placed) and if your region receives 762 mm of precipitation a year. If it receives less (between 254 mm and 762mm), 2 or 3 of these 300 gallon tanks can be placed (so that more rain can be gathered at times when it does rain). Also affecting tank size is predicted rainfall and rainfall variability; the higher prices for larger tanks; intended use of rainwater and typical consumption for these uses; the area of roof draining into the tank; security of supply desired.

One of the greatest revolutions in the ability of harvesting rain water has been the invention of modular, scalable systems which are installable underground. These came as an evolution of a geosynthetic applications called drainage cells, which when stacked provide a void space volume which allows for the storing of water. Improved and more cost effective industrial design now allow for theoretically limitless storage of water underground. Examples of these modular structures are Atlantis Matrix Tanks used in the Manly Stormwater Treatment and Re-use project of Manly Council

Manly Council

Manly Council is a Local Government Area on the Northern Beaches of Sydney, in the state of New South Wales, Australia.- Demographics :According to the , there:...

in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

Water supply augmentation

In some cities, installation of rainwater tanks 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

House Energy Rating

A House Energy Rating is an index of a building's thermal performance for residential homes in Australia....

. Some governments subsidise 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

Reclaimed water

Reclaimed water or recycled water, is former wastewater that is treated to remove solids and certain impurities, and used in sustainable landscaping irrigation or to recharge groundwater aquifers...

or seawater desalination

Desalination

Desalination, desalinization, or desalinisation refers to any of several processes that remove some amount of salt and other minerals from saline water...

. Tanks are often perceived to have environmental costs that are comparatively lower than other water supply augmentation options.

Rainwater collection can be made compatible with centralised water supply by tapping it using an electropump.

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.

Colorado law

In the State of Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, USA, the installation of rainwater collection barrels is subject to the Constitution of the State of Colorado, state statutes and case law . This is a consequence of the system of water rights in the state; the movement and holding of rainwater is inextricably linked with ownership of water rights and is enshrined in the constitution

Constitution

A constitution is a set of fundamental principles or established precedents according to which a state or other organization is governed. These rules together make up, i.e. constitute, what the entity is...

of the State of Colorado. The use of water in Colorado and other western states

Western United States

.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

is governed by what is known as the prior appropriation doctrine. This system of water allocation controls who uses how much water, the types of uses allowed, and when those waters can be used. This is often referred to as the priority system or "first in time, first in right." Since all water arriving in Colorado has been allocated to "senior water right holders" since the 1850s, rainwater prevented from running downstream may not be available to its rightful owner. In 2009, legislation in Colorado was enacted that permits capture of rain water for residential use subject to strong limitations and conditions. In order to be permitted, a residence may not be connected to a domestic water supply system serving more than 3 single-family dwellings. The permit must be purchased from the State Engineer's office and is subject to water usage restrictions.

Calculating rainwater collection

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

1 inch of rain on a 1000 square feet (92.9 m²) roof yields 623 gallons (2358 litres) of water; or
1 cubic foot equals (12 inch by 12 inches (304.8 mm) by 12 inches (304.8 mm) cube) equals 7.48 gallons; or
1 millimeter of rain on a 1 square meter surface yields 1 litre of water.

Internal rainwater tank

Rainwater tanks or drums may be used inside a house to provide thermal mass for a trombe wall

Trombe wall

A Trombe wall is a sun-facing wall separated from the outdoors by glass and an air space, which absorbs solar energy and releases it selectively towards the interior at night. The essential idea was first explored by Edward S. Morse and patented by him in 1881...

(or water wall). Rainwater HOG

Rainwater Hog

Rainwater HOG is a modular water storage tank which can be used horizontally or vertically for Rainwater Harvesting, emergency water storage and post-filter greywater storage...

modular tanks invented by Sally Dominguez

Sally Dominguez

Sally Dominguez, , practised sustainable architecture for 9 years before designing the award-winning Nest high chair now held in the Permanent Collection of the Powerhouse Museum...

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 high r value of the stored rainwater to add effective thermal mass to the enclosed spaces.

Specially designed rainwater tanks can also be embedded in or under the concrete slab

Concrete slab

A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 10 and 50 centimeters thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving.In many domestic and...

of a building (stab tank).

A house in Cape Schanck Victoria, Australia

Australia

uses an internal rainwater tank to provide cooling to the living room in summer. During winter the tank is drained and wrapped in an insulating jacket. The tank also provides structural support to the roof, and excess water is used for domestic use including drinking.

External links

Code of Federal Register - CFR Title 21 Part 129 Helpful information and water tank installation instructions. This is a US Government document, published as part of the Federal Register, these are both government rules and guidelines of water tank installations.
The Texas Manual on Rainwater Harvesting
Guide on saving water around the garden.
Waterwise - Reducing Water in the UK house
Rain barrel construction - Great Lakes Green Initiative
Building a water barrel system
Example and instructions for closed barrel system

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.