Precious Water: Sustainable Indoor Water Systems
Faucet Efficiency
EPAct included requirements for faucet flow rates. Residential lavatory faucets must be regulated by an aerator to 2.2 gallons per minute (gpm) or less, kitchen faucets to 2.5 gpm or less. Commercial faucet requirements vary by fixture type: handle-operated models are regulated by aerator to 0.5 gpm, while self-closing and sensor-operated ones are limited to less than .25 gallons per cycle.
As usual, however, the technology available is far greener than EPAct. While kitchen faucets need about a 2.5 gpm flow rate in order to fill a pot in a timely fashion, residential lavatory faucets can be satisfactory for the user when reduced to even a 0.5 gpm flow rate, and conservation-minded specifiers have begun to recommend aerators which deliver that flow rate. In commercial washrooms, metered faucets are common. These are generally mechanically operated fixtures that deliver water (at no more than .25 gal/cycle), then self-close. Many of these devices are built to allow the user to adjust the temperature before operation.
In most commercial washrooms, however, sensors are becoming the standard. But engineers have reached the limit of water-efficiency for sensor models: 0.08 gallons per cycle. Ironically, it is not user demand or engineering limitations which make this the limit. Rather it is the fact that other environmental considerations come into play. At less than 0.08 gal/cycle, battery disposal (or power use) takes a greater toll on the environment than is represented by the water that might have been saved.
The Massachusetts Water Works Association's Raymond Jack reminds project leaders that end-user considerations must come first, especially for specialized institutional projects. Take a senior center, for example: Such a residence will have aspects of multi-unit residential and healthcare facilities built into the configuration, but must also feel to its occupants like a home. No one has sensor-faucets at home, and furthermore they won't allow users to adjust the water temperature-a feature anyone would expect at home. In addition and interestingly, when one arrives at the most ergonomic model for seniors, one has probably arrived at the most water-efficient model. "An older person will likely have some difficulty with their hands," says Jack. "If that person has to fumble with two possibly stiff and difficult-to-manage handles to start the water and adjust the temperature, a great deal of water will have been wasted before the user begins to wash." Jack suggests single-lever faucet fixtures for these situations, which will save water-enough to pay for the more expensive fixture in a relatively short time.
Shower Efficiency
As illustrated in an old Seinfeld television program, poor showerhead performance drives otherwise sane people to pester friends and family for a place to get "a good shower"-even to the "black market." (Kramer buys a model intended for "hosing down elephants in the circus.") Is there a point at which user acceptance must trump any advance in conservation technology?
The answer is yes: 2.5 gallons per minute. This flow rate is both the EPAct requirement and the LEED baseline. Attempts to reduce the flow rate still further are mostly met with very unhappy users. Some users even remove the flow restrictors from their fixtures, producing rates of 4 gpm to 6 gpm, which is clearly not green by any standard. Also, flow rates below 2.5 gpm risk failure of certain types of thermostatic mixing valves, leading to scalding of the user. When specifying valves and showerheads, it is wise to consult the manufacturer of the valve; the information may help avoid this problem altogether, and no one gets burned.
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LEED® and Indoor Water Conservation
Architects, engineers and other building construction and operations professionals will no doubt already be familiar with the Leadership in Energy and Environmental Design (LEED) Green Building Rating Systemâ„¢. Most may not be aware, however, that LEED ratings are based on a number of green standards, including a number for water conservation.
LEED-NC, the system for New Construction projects, is based on a scoring system of 69 total possible points, 5 of which are for water efficiency techniques. Up to two points are awarded for reducing by 50 percent--or for eliminating--potable water used in irrigation of landscaping. Another is awarded for achieving a significant reduction in wastewater, either by recycling it or treating it onsite. Relevant to our article are the LEED NC credit points for water-efficient indoor fixtures. Reduce use by 20 percent as compared to a calculated baseline, and the project gets the first point; the second point is awarded when the project achieves a 30 percent use reduction.
As seen in various available technologies, these two points are certainly achievable, and a reasonable client will understand the long-term benefits and savings. Then all a designer or engineer has to do is specify plumbing products that save water without compromising performance.
The same two points are available in a number of LEED rating categories, such as for Commercial Interiors (LEED-CI) and LEED for Retail (now in its pilot program). In LEED-EB, which is for retrofits of Existing Buildings, the points are awarded for 10 percent and 20 percent reductions from the baseline. LEED's new program for Schools is more ambitious, offering a third point for a 40 percent reduction in potable water use. LEED for Schools also offers a point for reduction of process water use; the idea is to maximize the efficient use of water within the school buildings so as to decrease the burden on the municipal water supply and on the wastewater system.