Achieving greater water efficiency will require improved technology, reduced hardware costs, consumer behavioral changes, legal and policy changes in health codes, and re-interpretation of some water laws. Graywater systems must get less expensive and easier to maintain. Installation costs can exceed $10,000 for a whole-house system, not counting ongoing maintenance and electricity. If 30,000 gallons of water per year is saved for a household of four, the economic benefit is just $300 per year—a 30-year payback for the capital costs associated with the system. Even an installation cost of $3,000 will have a payback exceeding 10 years once maintenance is considered. Until whole-house graywater systems can be installed for under $1,000 per house, the economics are not likely to favor widespread adoption, even if the cost of water dramatically increases.
There are other significant barriers to the widespread implementation of graywater recycling. Health codes will need to be modified to incorporate standards for the filtration and treatment of graywater to enable health departments to assess risks associated with the use of this water and to permit installation of these systems.
Some important progress has been made. The International Association of Plumbing and Mechanical Officials has approved a graywater code section in Chapter 5 of the Green Plumbing and Mechanical Code Supplement, now Chapter 16 of the Uniform Plumbing Code. The water rights issues associated with graywater may be more challenging, depending upon the jurisdiction. A strict interpretation of a “single-use water right” may prohibit the use of graywater recycling. Some cities in the western United States have only single-use water rights. In regions where water can be used to extinction, water rights should not pose a barrier to graywater recycling.
Landscape guidelines need to be in place to address regional irrigation requirements and to define improved irrigation technologies. In wet regions, high-water-use plants and large turf areas can remain. In dry regions, only plants that can manage with minimal irrigation will be included. Tools like advanced irrigation control technology, including soil moisture sensors, rain sensors, and evapotranspiration weather stations, have become more affordable over the past 10 years. This is good news for consumers, but the key to achieving 20 gpcd is to eliminate wasteful irrigation entirely.
The landscape itself should be designed to rely on available precipitation supplemented only with small volumes of reuse water. And the key to this is using smart technology, from microsensors to multi-zone drip systems. High-pressure irrigation systems like those we use today will only be an option for parks and large landscapes. Low-pressure, micro-managed drip irrigation that uses recycled graywater will be the state of the art.
And the technology to produce the resource-use dashboard described in Alejandra’s kitchen exists today and is in use in green commercial buildings with sophisticated metering, but residential dashboards are still rare because of the lack of household meters that can provide real-time feedback. Even though dashboards can be created with the monthly water meter readings of today, their true informational value will not be realized without a smart meter that delivers information on up-to-the-minute water use. Advanced metering infrastructure is expensive, and while these meters are increasingly being installed by water utilities, few have harnessed the potential power of these systems to provide customers real-time information on consumption.
THE FUTURE IS WAITING
Indoor water use is dropping with new high-efficiency plumbing fixtures and appliances. Outdoor water use can be reduced with technological improvements in sensors and irrigation equipment. These advancements will bring us closer to the hyper-water-efficient home of 20 gpcd. What we further need are approvable and affordable graywater systems, widespread smart metering, and readily available sensor technology. All of this is possible by 2020. Where the impediments are most serious are where water rights laws will prevent water capture and reuse at the individual household level.
Overcoming these challenges will be well worth the effort: If we can achieve nationwide a residential usage level of 20 gpcd or less, that would mean that a city such as Phoenix could reduce its overall water demand by 70% or more. Our sustainable water future needs this!
Mary Ann Dickinson is executive director of the Alliance for Water Efficiency (AWE) and Vision 2020 Water Efficiency co-chair with Carole Baker, chair of AWE. Peter Mayer is vice president of Aquacraft, Inc., a firm that specializes in residential end-use measurement.