While hard data on total water use in buildings is somewhat difficult to come by, the U.S. Green Building Council estimates that buildings account for 14% of domestic water consumption in the U.S.¹ Other sources report 12%—a relatively small percentage compared with, say, agriculture, but it represents tens of billions of gallons of domestic water consumed every day.²
In addition to the millions of single-family homes in the U.S. and Canada, hospitals, laboratories, industrial facilities, apartment and condo complexes, commercial kitchens, sports arenas, hotels, and office developments are particularly large consumers of domestic water for interior uses. For instance, toilets in commercial buildings alone consume 1.2 billion gallons of water a day.³
There are also severe inefficiencies in the system. For example, EPA WaterSense estimates that 80% of the 12 million urinals in the U.S. use up to five times the federal standard of 1.0 gallons per flush and waste more than 150 billion gallons of fresh water a year, enough to supply 1.5 million homes.4
In the U.S., the Energy Policy Act of 1992 first brought the issue of water conservation to light by banning the installation of toilets that consume more than 1.6 gpf—a move that led to outcries from building owners and homeowners for awhile, until manufacturers, plumbers, and contractors could work out the mechanical problems of the early units. Since then, new regulations, the growth of the green building movement, and significant improvements in plumbing products have enabled Building Teams, homeowners, and property owners to drastically cut water use in buildings.
This past August, Los Angeles became the first U.S. city to mandate high-efficiency fixtures in all new buildings and major renovations. The ordinance, which kicks in December 1, limits toilets to 1.28 gallons per flush and urinals to 0.5 gpf. The regulation also requires high-efficiency faucets (2.2 gallons per minute), pre-rinse spray valves (1.6 gpm), showerheads (2.0 gpm), commercial dishwashers (0.62-1.16 gallons/rack), and, starting next year, pint-flush urinals (0.125 gpf).5
Other cities in California are expected to follow suit in light of the statewide drought.4 And it's only a matter of time before jurisdictions throughout the U.S.—especially those in water-scarce regions like the Southwest—mandate the switch to high-efficiency water technology.6
Earlier this year, the U.S. Green Building Council raised the bar for green buildings with the release of LEED 2009. LEED now requires a 20% reduction in water use as a prerequisite and increases the number of Water Efficiency credits in its various programs. Even more drastic is a new requirement for LEED-certified projects to submit performance data on water (and energy) use for five years after certification.
These increasingly stringent standards and regulations—along with large-scale drought and water scarcity in a growing number of regions of the country—are driving demand for water-saving systems and technologies. Manufacturers have heeded the call by providing a slew of low- or no-flow products, sensor-activated devices, graywater recycling systems, and water submetering technology (Table 3.1).
And Building Teams are responding. According to the BD+C/Professional Builder 2009 White Paper Survey, most Nonresidential Survey respondents said their firms are already using an average of 9-10 water-saving technologies and expect their firms to make use of 13-14 such systems in the near future. High-efficiency lavatory faucets (1.5 gpm or less), sensor-activated faucets, and sensor-activated flush valves are the most commonly specified technologies, followed by high-efficiency showerheads (2.0 gpm or less), water metering devices, tankless water heaters, and high-efficiency urinals. Waterless urinals, dual-flush toilets and flush valves, and high-efficiency dishwashers are also gaining popularity with Building Teams (Table 3.2).
In certain building types, such as offices and schools, implementation of these interior water-saving technologies alone can cut overall water consumption by 30% or more, with payback periods as short as three years on certain technologies. High-efficiency toilets and faucet spray aerators can have the quickest payback, especially in retrofit projects.4
A case in point: The Parc 55 Union Square Hotel in San Francisco is saving $170,000 a year on water and sewer charges after replacing more than a thousand 3.5-gpf toilets with pressure-assist 1.0-gpf units, according to a third-party research report. The hotel is saving nearly a million gallons of water every month, and its toilet-related maintenance calls have been cut in half.7
“When it comes to conserving water in buildings, the first step is to look at the plumbing fixtures,” says Heath Baxa, PE, LEED AP, a project manager and head of sustainable design with M-E Engineers Inc., Wheat Ridge, Colo. The next step, says Baxa, is to look at the feasibility of reusing water on the site, and “that's where things get more complex.”
Graywater for flushing: The next wave?
Installing water-efficient fixtures, industry experts say, will only take water conservation so far, perhaps to a 20-30% reduction in use. Shooting for a reduction of 40% or more will most likely require Building Teams to look at ways to reuse water. Inside buildings, that means using graywater—primarily the wastewater from bathroom sinks, showers, and clothes washers—to flush toilets and urinals.
To date, the use of graywater for flushing has been pretty rare. Only 21% of AEC respondents to the 2009 White Paper survey said their firms had specified graywater reuse systems in the past two years, even though the potential for water savings using graywater is significant, especially in office buildings, schools, hotels, and multifamily developments. And, unlike rainwater harvesting, where the water supply depends on the whim of Mother Nature, commercial and multifamily buildings provide a relatively constant source of graywater. “In a large office building, just the water from sinks can be significant on a daily basis, certainly enough to flush many toilets and urinals,” notes green building consultant Jerry Yudelson, PE, MBA, LEED AP in his August 2009 report to the Mechanical Contractors Association of America Research Foundation.4
Despite growing demand and unrealized potential for graywater reuse in buildings, however, plenty of hurdles remain for those looking to implement graywater systems for toilet flushing.
First, there's the cost hurdle, both the cost of the systems themselves and the cost of the space associated with tanks, pumps, and treatment, not to mention the need for dual-piping to separate graywater from potable water. “Those are the biggest obstacles,” says Julie Paquette, PE, LEED AP, an associate with the Green Integration Group, R.G. Vanderweil Engineers, Boston. Even in Boston, where water rates are well above the national average, Paquette says owners balk at the long payback and O&M requirements of water reuse systems.
The next hurdle: building and plumbing codes. Many jurisdictions simply have not caught up with the technology, forcing Building Teams to invest a lot of time asking for special approval for alternative approaches. “Even the mere threat of a construction delay or additional preparation costs frightens many owners from pursuing established alternative water-conservation strategies,” says Jeffrey Gaines, AIA, LEED AP, a senior associate, manager of programming and planning, and sustainable design committee leader with Albert Kahn Associates, Detroit.
Some states and localities make it really hard to use graywater. Until recently, for example, Oregon required applicants to obtain a water quality permit comparable to that for a municipal wastewater treatment plant. Coupled with high permit fees, this requirement effectively killed graywater reuse in the state. This past June, Oregon changed its law to allow graywater to be used for “beneficial uses,” such as flushing toilets and urinals and irrigating certain trees and plants.8
Code officials and plumbing boards justify their position by saying that their first responsibility is to protect the public's health and safety and that graywater, if not treated properly, could become a breeding ground for microorganisms and other potential health hazards. In the absence of science-based quality standards for graywater reuse (something several plumbing manufacturers are trying to develop), they say, graywater reuse should be limited to underground drip irrigation at best.
Code officials also point to potential maintenance problems with graywater systems, especially in homes. They argue that if many homeowners have trouble maintaining simple things like water heaters, how can they be expected to maintain complex graywater treatment systems? In response, the Alliance for Water Efficiency suggests that manufacturers could offer lifetime maintenance programs, or local jurisdictions could require periodic inspections of such systems.9 Either way, there would be added costs.
The International Code Council and IAPMO are working on the problem. For example, IAPMO's Green Plumbing and Mechanical Code Supplement, due out next February, introduces language pertaining to the use of graywater recycling and rainwater harvesting, with the goal of speeding the code review and approval process for these new technologies (more on this in Chapter 5, page WP33).
California's Department of Water Resources is in the process of adopting statewide standards for installing dual plumbing systems—one for potable water, the other for recycled water—within virtually any commercial and institutional building type. If adopted in January, the code would allow recycled water to be used in toilets and urinals, air-conditioning devices, cooling towers, and floor trap priming. Building owners would have to implement health and safety measures, such as cross-connection testing, installation of purple-colored pipes, and posting of signage in rooms that utilize recycled water or house recycled water equipment.10
Despite the obstacles, demand for graywater recycling is expected to grow as code bodies and jurisdictions become more accepting of these technologies and costs for implementation come down. Half of the respondents to our Nonresidential Survey and nearly a quarter respondents to the Residential Survey said they plan to install these systems within the next two years. One sign of a budding graywater market is the growing number of off-the-shelf solutions being developed by manufacturers (see sidebar, page WP21).
Drain line transport issue: How low can we go?
One huge concern among plumbing engineers and contractors is the possibility of clogging that could occur in drain lines when new water-efficient fixtures are installed. Greater efficiency leads to less water in the drain lines, meaning that there may not be enough water to flush waste down the pipes.
“When the industry went from 3.5 gallons per flush to 1.6 in the 1990s, there was a lot of talk about drain lines drying up; now we're going to 1.28 and even lower to one gallon per flush,” says Pete DeMarco, IAPMO's director of special programs. “We know that somewhere between 1.6 and zero gallons per flush, building owners are going to have problems with clogging because there won't be enough wastewater in the system.”
This problem can be especially nettlesome in large commercial projects such as shopping malls, office complexes, and warehouses that have long, horizontal drainage lines to the sewer. A 2005 study of nine high-efficiency toilets using four drain line diameters and slope configurations found greater potential for waste remnant and potential blocking with drain lines as short as 50 feet (with four-inch-diameter pipe at a 1% slope) if no supplemental flows are present.11
While there have been no major cases of drain line clogging involving high-efficiency fixtures in the U.S., building owners in Europe and Australia have recently reported problems. Last year, the city of Tucson, Ariz., was so concerned with possible backup in its sewer lines (which can lead to dangerous and malodorous hydrogen sulfide concentrations) that it suspended its program of retrofitting low-flow toilets in older neighborhoods.
Concerned that manufacturers may be reaching a “tipping point” in how low they can go in water efficiency, five plumbing industry groups have formed the Plumbing Efficiency Research Coalition with the goal of sponsoring an extensive research study on drain line carry. According to IAPMO's DeMarco, who is coordinating the project for PERC, the study will 1) use computational fluid dynamics to model how far waste will travel under various guidelines, 2) conduct laboratory mockup tests of cast iron and PVC piping in three diameter sizes, and 3) field test actual plumbing systems.
PERC hopes the research findings will help designers on new projects or retrofits to take into account both current—and future—levels of wastewater flow when designing drain lines. This may involve adding more pitch to pipe runs, avoiding long, horizontal drain lines, and reducing the number of elbows.
|Technology||Current base||Most efficient||Future possible||Comments|
|Sources: Environmental Building News, February 2008; U.S. EPA|
|Toilets||1.6 gpf||0.8 gpf (pressure-assist and dual-flush units)||Water-free composting toilets (niche technology: remote buildings, demonstration green projects)||• Progressive jurisdictions are moving toward 1.28 gpf as the standard • Dual-flush is gaining share in women's restrooms|
|Urinals||1.0 gpf||0 gpf||“Blue cube” converts installed, standard-flush urinals into 99% water-free units||• Pint-flush (0.125 gpf) units quickly gaining market share • New WaterSense label defineshigh-efficiency as 0.5 gpf|
|Showerheads||2.5 gpm||1.5 gpm||Innovations in performance and user experience by maximizing droplet size and spray force with less water||• WaterSense label defines high-efficiency as 2.0 gpf • Hotels slow to adopt low-flow (due to guest complaints)|
|Faucets||2.5 gpm at 80 psi; 2.2 gpm at 60 psi; 1.5 gpm at 60 psi (residential lavatory faucets)||0.5 gpm||• Innovations in faucet/aerator design to create perception of strong flow • Improvements in sensor technology||Studies show that sensors may increase water use by activating unnecessarily and operating longer than needed|
|Pre-rinse spray valves (commercial kitchens)||1.6 gpm||1.28 gpm||These devices typically use more water in commercial kitchens than dishwashers|
|Hot water circulation systems||Continuous-circulation systems (maintain a loop of circulating hot water, reducing wait time)||Demand-controlled hot water circulators (improved energy efficiency by delivering hot water only when needed)||• Save water, but increase energy use • Common in hotels and residential • Alternative: greater hot water pipe insulation|
|Commercial clothes washers||1.26 MEF (modified energy factor); 9.5 WF (water factor)||1.72 MEF; 8.0 WF (Energy Star threshold)||Huge potential for graywater capture and reuse||Large commercial washing systems used in hotels and hospitals not addressed by Energy Star or other federal standards|
|Commercial dishwashers||1-1.7 gal/rack (under counter); 0.95-1.18 gal/r (stationary single-tank door); 0.7-0.79 (single-tank conveyor); 0.54 (multi-tank conveyor)||0.28 gal/rack||Innovations in spray nozzle design, chemical additives, and water temperature to speed washing time||Water use varies widely based on model type|
|Used in last 18-24 months||Expect to use in next 18-24 months||Used in last 18-24 months||Expect to use in next 18-24 months|