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ARCSA Frequently Asked Questions

What is the mission of ARCSA?
The mission of the American Rainwater Catchment Systems Association ( is to promote sustainable rainwater harvesting practices to help solve potable, nonpotable, stormwater and energy challenges throughout the world.

Can you tell me more about ARCSA and what it offers?
ARCSA ( is a 501(c)(3) nonprofit with close to 1000 members in 14 nations, including large businesses, individuals, regulators, water purveyors, elected officials, manufacturers, designers, utility officials, installers, sustainability advocates, system maintainers, architects, plumbers and other enthusiasts. ARCSA offers resources, documents, presentations, webinars and discussion forums on its website and is the only organization that offers an Accreditation program for rainwater harvesters. We have also recently created an advanced "Certified Professional” status that builds on the Accredited Professional training. To learn more about the Accredited and Certified Professional programs, consult this link, contact or call 512-617-6528.

How do the components of ARCSA’s mission relate to one another?
The most enlightened rainwater harvesting practices involve a recognition and exploitation of the relationships among ARCSA’s mission components. For example, sustainable harvesting of rainwater for gravity-fed nonpotable drip irrigation diminishes the stormwater impact of rain events, decreases the water-energy footprint and displaces the need for an equal amount of highly treated potable utility water.

What influence or reach does ARCSA have internationally?
ARCSA joined the International Rainwater Harvesting Alliance (IRHA), the International Rainwater Catchment Systems Association (IRCSA) and 30 other groups from around the world in endorsing the use of rainwater as a tool to address water-related problems and to provide a regular supply of safe, accessible and affordable drinking water in sufficient quantity to the world’s population, as called for by the UN Human Rights Council.

While ARCSA’s membership is predominantly in the United States and Canada, the organization has members in 12 other nations and regional representatives in Australia, Ireland and England.

How can people in my city find a qualified designer and installer for a rainwater harvesting system?
The ARCSA website menu includes a robust member search engine, Find a Pro in the ARCSA Resource Guide which effectively identifies members within a selected radius of a zip code.

Rainwater Harvesting — General Questions

Why is rainwater harvesting important?
One of the principles of rainwater management is to slow the water by collecting and using it onsite and slowly infiltrating any excess overflow. Collected rainwater can be an important source of high-quality water for crops, greenhouses, livestock and humans even in very arid climates.

What is the history of rainwater harvesting?
Rainwater harvesting has been used for thousands of years. The Old Testament mentions cisterns at least ten times, and rainwater harvesting systems in the Middle East date to 5,000 years ago. In the U.S., water shortages, quality concerns and stormwater mitigation have renewed interest in this ancient practice.

Besides the obvious environmental benefits, what other advantages does rainwater harvesting offer?
The most enlightened rainwater harvesting practices involve a recognition and exploitation of the relationships among the four components of ARCSA's mission: potable, nonpotable, stormwater and energy. For example, sustainable harvesting of rainwater for gravity-fed nonpotable drip irrigation diminishes the stormwater impact of rain events, decreases the water-energy footprint and displaces the need for an equal amount of highly treated potable utility water.

What are some other uses for harvested rainwater other than irrigation and drinking water?
Rainwater can be used for any potable or non-potable use.

Water from my utility is very cheap. How does a rainwater harvesting business compete with subsidized, inexpensive utility water?
There are many reasons to harvest rainwater: quality of the resource; reduced appliance maintenance due to low mineral content; availability of a secure, onsite water source; and greater nutritional value for crops and gardens. Some successful rainwater harvesting businesses are growing because they make Return on Investment arguments to potential clients. Their rationale is based on the current and growing cost of utility water, the value of a rainwater harvesting system relative to other potential investments, the ability to mitigate costly stormwater effects, the quality of rainwater relative to utility water, the relative security of distributed water systems and — for a select few — the altruistic benefits.

How does the quality of rainwater as a resource compare to ground- and surface-water used by utilities?
Increasingly, consumers are attracted to rainwater for the quality of the resource. While surface and ground waters suffer from contact with the contaminants that are plentiful in those water sources, rainwater has fewer contaminants to deal with, and those can be reduced or eliminated by discarding the first portion of each rain event by using a "first divert" system, and by using the components and materials approved by the National Sanitation Foundation for rainwater collection. As a testament to the quality of rainwater, ARCSA endorsed six rainwater entries in the prestigious Berkeley Springs [West Virginia] International Water Tasting competition held in February, 2011. Rainwater from Texas-based SparkleTap won First Prize in the Purified Water category, and Virginia-based RMS took fifth place. Click here for details.

Shouldn’t we be conserving water by decreasing the demand before we go to the expense of increasing the supply through rainwater harvesting?
Rainwater harvesters are first conservation and efficiency advocates. It makes no sense to spend precious funds to augment water supplies if one has not first extracted the greatest benefit from water efficiency and conservation opportunities.

In a related sustainability field, the same is true of exhausting energy efficiency and conservation opportunities before installing a photovoltaic system. If one was driving down the road and found that one’s parking brake was on, the first solution would be to release the parking brake, not to add more power by buying a bigger engine. Thus if one has not implemented water conservation and efficiency opportunities, it is premature to harvest rainwater.

Over the past few years, have you noticed increased public interest in rainwater harvesting? Do you think a water treatment business would be wise to expand into rainwater harvesting?
A recent survey of the US rainwater harvesting market reveals substantial growth in the face of an otherwise stagnant economy. While it may appear that harvesting rainwater is simple, the best rainwater harvesters are multi-disciplined professionals. We strongly recommend that aspiring rainwater harvesters join ARCSA, avail themselves of one of ARCSA's periodic rainwater harvesting Accreditation workshops and apply for Accredited Professional designation. The two-day program is designed to take someone who is aware of the fundamentals of rainwater harvesting to the next level through instruction in the proper design, installation and maintenance of a rainwater harvesting system. ARCSA has also created a "graduate" level” certification — the Certified Professional — which is a designation available to an Accredited Professional who fulfills 48 hours of classroom or webinar instruction, attends a two-day Design and Construction workshop and passes a rigorous examination.

What impact will global warming likely have on the annual rainfall and type of rain event in my region?
The impact of climate change will vary greatly from region to region, but most studies agree that climate change will result in more intense storms, and these storms would result in more water runoff. Rainwater harvesting allows us to capture this runoff, put it to a useful purpose and slowly infiltrate overflow.

Rainwater Catchment Systems

What are the major components of a rainwater harvesting system?
The major components of a rainwater harvesting system are the collection surface, gutters, downspouts, pre-filtration systems or first-flush devices, storage tanks and distribution systems — which can include sanitization.

I’m familiar with rain barrels. Can rainwater be harvested on a large scale?
Modern tanks used for residential and commercial applications are available in all sizes and can exceed one million gallons. The Romans built huge cisterns under Istanbul; the largest stored 80,000 cubic meters (21 million gallons).

What special components or treatments are necessary to make rainwater safe to drink?
Rainwater must be treated to be safe to drink. The U.S. Environmental Protection Agency publishes drinking water standards that define the maximum contamination level for potable water in the U.S., and while they apply only to public water supplies serving more than 25 people, it is prudent to apply the same requirement to smaller systems.

Legislation, Codes and Ordinances

I’ve heard that compliance with EPA stormwater rules is a big driver for installing rainwater harvesting systems. Please explain.
One of the most frequent drivers for rainwater harvesting is compliance with the EPA's and states’ stormwater rules. Well-designed rainwater harvesting systems will make full onsite use of the rainwater, in most cases slowing it down until it is infiltrated on property, so it does not become problematic stormwater.

How would you describe governmental awareness of rainwater harvesting and its ability to help solve water problems?
There is a growing awareness in the U.S. that rainwater harvesting is at least a partial solution for potable, nonpotable, stormwater and energy challenges. National, state and local jurisdictions are developing legislation, codes and ordinances that encourage the practice.

What is the status of national codes that support rainwater harvesting, and when can I expect that my building codes will be supportive?
ARCSA Design and Installation Standards have been incorporated into the IAPMO Green Plumbing & Mechanical Code Supplement of the Uniform Plumbing Code (UPC), and the International Green Construction Code of the International Plumbing Code (IPC). States will refer to their reference plumbing code (either the IPC or UPC) and can be expected to incorporate these new standards over the next three years.

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