Graywater Use in California Single and Multi-Residential Units (2012)

Published: September 25, 2012

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Responsible sustainable management of global water resources is one of the primary challenges of the 21st century. This is particularly true in California, where source waters and their ecosystems are stressed and degraded due to current management strategies in the face of agricultural needs, population growth, urban sprawl and climate change.

California has a history of naturally varying hydrological conditions. It is common for our region to experience short periods of wet weather, followed by extensive periods of drought. In the last 100 years, we have been in a drought for 35 years, roughly one third of the time.1 Over the past decade, the average early snowpack in the Sierra Nevada, the main source of the state’s water supply, has decreased by about 10%.2 Given the state of water supplies in California, and the corresponding water quality issues, water conservation and water reuse strategies are necessary to institute as norms in California at all times, not just during drought periods.

Large areas of California are desert demanding nonlocal water sources for expansive human developments. Water supplies for Southern California travel distances up to 1800 miles from headwaters to destination, as exemplified as the Colorado’s voyage to which San Diego. Other Southern California cities utilize water from the San Francisco Bay Delta (SFBD) and the Owens River Valley, moving 400 miles or more through large open canals in the Central Valley. Pumping this water up and over the Tehachapi Mountains to the Los Angeles Basin spends 2% of the state’s total energy use.3 This points to the intricate connection between water use and energy use – using one resource, always includes a corresponding use of the other resource.

Water users in California also acquire their water supplies from the ecologically crucial San Francisco Bay Delta, one of the largest estuaries on the western coasts of North and South America. Our best option is to participate as fellow-members of this ecosystem, as opposed to externalized managers, and consider how water conservation and water reuse is able to support maximum health of this important estuary.

Californians needs to make a concerted effort to both limit our draws on natural water bodies and control the quality of effluents sent back into the environment. Before considering alternatives to increasing the available water supply, we should first ensure that the available water supply is being used efficiently. Employing water conservation and reuse strategies are crucial steps in protecting this vital riparian ecology.

When it comes to water security, the first step is to use and reuse water as many times as is safe and economical. The state of California and local jurisdictions should encourage safe and legal water reuse as it allows the maximization of water’s utility on-site and encourages the treatment of used water prior to discharge. Graywater reuse at the domestic level is one of the simplest forms of water reuse and should be investigated and encouraged as a means to reduce the impact of residential developments on water resources.

Graywater reuse contributes to resource efficiency and sustainable, localized water management. LEED, the International Code Council with “National Green Building Standard,” and The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) with “Standard 189.1-2009 - Standard for the Design of High-Performance Green Buildings” all recognize the use of graywater to satisfy the option for water use reduction.

Legislative and executive drivers, such as the Clean Water Act, and the various iterations of Energy Policy Acts also point to water reuse as both water and energy sensitive strategies for reduction of demands on our resources.5 Graywater has the potential to reduce the demand for new water supply, reduce the energy and carbon footprint of water services, and meet a wide range of social and economic needs. In particular, the reuse of graywater can help reduce demand for more costly high-quality potable water. Graywater also satisfies the adage, “Never use water once that you can use two or three times more.”

Historically, in California, graywater systems have been installed largely as unpermitted, ad hoc systems designed by the residential water reusers. Art Ludwig of Oasis Design estimates that there are over 1.7 million illegal graywater systems in California.6 These systems range from informal bucketing systems that convey water from shower “warm-up” water to laundry to landscape all the way through to systems that gather water from kitchen sinks and dishwashers.

Taking a graduated step towards facilitating safe and legal residential graywater use, in January 2010, the California Building Standards Commission adopted Title 24, Part 5, Chapter 16A into the California Plumbing Code. The new graywater code (now again under revision for the 2012 code revision cycle at the time of writing) addresses residential outdoor graywater use.


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