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LEARNING OBJECTIVES

Reading this article provides professional education in green building, including Sustainable Design (SD) and Health, Safety and Welfare (HSW) credits. Upon finishing, the reader should be able to:

• Describe general approaches to building water conservation and related topics in LEED certification programs.
• List building technologies designed to improve water conservation or water capture and reuse in nonresidential facilities.
• Discuss site and outdoor approaches for water efficiency.
• Explain the relative advantages of water-saving tactics including plumbing fixtures, mechanical systems and irrigation.

EDC is a registered provider with The American Institute of Architects Continuing Education Systems. To earn 1.0 AIA-HSW-SD learning unit, attendees must read this article in its entirety and take the 10-question quiz at the end of the article or online at www.edcmag.com/CEU and pass with a score of 80 percent or better.

EDC is also a USGBC Education Provider; this course is approved by USGBC for 1 GBCI CE Hour toward LEED Professional credentialing maintenance. LEED Professionals may submit their hours to Green Building Certification Institute (GBCI) under the “Professional Development/Continuing Education” activity type in “My credentials” at www.gbci.org. For those who pass the quiz with a score of 80 percent, a certificate of completion will be emailed to you.

The  urgency of green building design is felt most powerfully with water-consuming systems. First, there’s the global impact: The Natural Resources Defense Council estimates that around the world at least 1 billion people are routinely exposed to unsafe drinking water. Here at home, three of every five U.S. states have dealt with regional water shortages over the last decade, says the EPA.

Second, costs are creeping upward. In the federal sector alone, expenditures for water and sewer run upwards of $1 billion annually. Add to that utility charges and the infrastructure impact, water and the energy to clean and pump it carry a hefty cost for society as a whole. The daily tab is almost 5 billion gallons of water used in the United States at a shared energy cost of 150 million kilowatt-hours.

From the washroom spigot to the sprinklered lawn, control of water use brings a variety of benefits for building owners, too: Reduced operating costs, code compliance, certification for sustainability standards and a leadership role in addressing the unknown potential for shortages. Clearly, conservation practices for domestic and outdoor water use impact a facility’s overall energy profile, too. The systems have many moving parts and must withstand frequent user contact, so they relate directly to the building’s durability. These two facts make water efficiency an integral part of life-cycle analysis (LCA).

For sensible project planning, experts start by identifying the unique needs of each situation. Seasoned specifiers of plumbing systems and fixtures point out that conservation strategies are tied to building type, function and occupancy. For that reason, any project should begin by working with the end-user to understand their values and attitudes. (See the sidebar “Give Them A Sign,” page 77.) “The key to water efficiency in a commercial facility is to first direct the focus of the client and occupants on water conservation,” says Rich Mitchell, AIA, LEED BD+C, managing principal with Group Mackenzie, the Portland, Ore.-based A/E/C firm. “In addition, it is critical for a client to know how water-efficient systems should be maintained and operated, otherwise they may never perform as intended.”

Analyzing end-user culture — for both the design and operations phases — leads quickly to a prioritization of opportunities. This laundry list can then be consolidated as part of a cohesive plan. “The starting point is an integrated strategy relating to overall water use — not only addressing water-efficient plumbing fixtures, but process water and cooling tower water use,” says Ilana Judah, Int’l Assoc. AIA, OAQ, LEED AP BD+C, and director of sustainability with FXFowle, New York City. “Also, rainwater and stormwater calculations should be part of the equation.”

Life Cycle and Cost Benefit

From a water conservation standpoint, achieving water efficiency through load and resource reduction is very effective — often through the use of highly efficient fixtures and client engagement to reduce demand. Much indoor water use remains fairly constant during the course of a year, according to a study by the University of Colorado and water-engineering firm Aquacraft Inc.1 Toilet flushing is the most regular and predictable of all, for example, making LCA and ROI determinations straightforward. (And in the majority of buildings, toilets account for up to one-third of water use — the single highest use.)

On the other hand, say green-building experts like Dietrich Wieland, LEED BD+C, Group Mackenzie’s director of sustainability, “With water conservation through collection and reuse, we have typically found greater challenges with regard to the cost-benefit of the systems.” As an example, Wieland cites irrigation: Peak demand typically spikes during hot summer months when rainwater levels are low. So sprinkler systems end up oversized to accommodate peak demand — cost prohibitive from a payback standpoint — “or rendered ineffective when the system is needed most,” he says.

A valuable approach is to focus on free water sources, say seasoned project leaders. The main techniques include rainwater collection systems on the rooftop and elsewhere, as well as greywater reclamation technologies. The two are frequently combined. Waste lines from sinks and showers or stormwater runoff are routed to filtration and disinfection units for treatment and then back to supply piping for toilet flushing, subsurface irrigation, cooling tower supply and other uses. (See sidebar, “The Hidden Costs of Free Water,” page 77.)

The U.S. Green Building Council’s LEED certification systems have long encouraged these approaches through the Innovative Wastewater Technologies credit to “reduce generation of wastewater and potable water demand, while increasing the local aquifer recharge.” Reducing the amount of potable water used simply to move sewage is a top goal — why not use sink waste or roof runoff for this? — as is treating water for use onsite. For both credits, the goal is a 50 percent reduction.

While these water-capture techniques add to the building construction or retrofit budget, in some cases they reduce operating costs while adding soft benefits such as positive publicity and end-user edification. “Rainwater collection is gaining interest, namely in public facilities such as K-12 schools where it is also used as an educational tool,” says Martine Dion, AIA, LEED AP BD+C, a senior associate and director of sustainable design with Symmes Maini & McKee Associates (SMMA), Cambridge, Mass. “It brings savings mostly in potable water used for sewage conveyance.”

Rainwater harvesting on a building typically uses roof catchment, with gutters, downspouts and storage vessels. Some may employ drip irrigation or other built-in reuse techniques, according to the American Rainwater Catchment Systems Association, based in Austin, Texas. To estimate the potential rainwater harvest, expect about 0.6 gallons of water per inch of rainfall for every 1 square foot of catchment area. For a 10,000-square-foot roof, that’s 6,000 gallons of water per inch of rainfall.

Dion points to several recent SMMA projects that have reached between 30 percent and 40 percent water efficiency. For Wellesley High School in Massachusetts, for example, low-flow fixtures save 860,665 gallons annually, and a rainwater capture setup that mainly serves toilet flushing reduces potable water demand by another 600,000 gallons — about 80 percent of the total need for conveying sewage. Similar approaches have worked for office buildings, says Dion, including a LEED Gold tower in Providence, R.I., that uses rainwater for cooling tower supply.

Savings from Mechanical Systems

In fact, cooling towers are a likely new focus for green buildings. “LEED now has a pilot credit for cooling-tower water makeup, and we anticipate that LEED 2012 will incorporate a credit exclusively for this,” says FXFowle’s Judah. “Controls and submetering for cooling tower water are also critical.”

The total savings can be considerable: A recent LEED project, the Marshall Space Flight Center in Huntsville, Ala., implemented cooling tower upgrades to address a poorly performing HVAC system. It saved 800,000 gallons of water in just the first eight months for the 4.5 million-square-foot facility.2

For cooling towers and other heating, ventilation and air conditioning (HVAC) systems, the key to water conservation is eliminating leaks and then optimizing system features. According to the DOE’s Federal Energy Management Program, water exits the cooling tower through evaporation, drift and blowdown. Add these together and you have the cooling tower’s total need for makeup water. Cutting down evaporation — which rejects heat to cool the building — can improve water efficiency, but may only save a small amount. Blowdown, or bleed-off, is the biggest opportunity, describing control of dissolved solids accumulating in the cooling tower, which cause corrosion and scale. Then there’s drift — the mist carried away from the tower — which can be controlled with baffles and eliminators to save even more.

Of course, leaks and overflow conditions also waste water and should be avoided or corrected immediately. This is true in heating systems, whether steam or hot water, which depend on careful maintenance and good insulation to remain water efficient. One retrofit option is to add a condensate return system, which can cut water supply needs by up to 70 percent. This also reduces the amount of chemicals required for treating system water — another cost-effective benefit — while lowering energy costs, as condensate water is already warmed when it again reaches the boiler.

Other trouble spots for HVAC water use include single-pass cooling systems where water runs through once, such as ice machines or some air conditioners. Engineers can modify many single-pass systems to make them closed loops, or they can add automatic shutoff controls. Another strategy is to use the effluent for boiler makeup or for landscape irrigation.

In all cases, the best mechanical systems are leak-free, well insulated and connected to the building and site ecosystem, taking water where needed and providing it, too.

Smart Water Systems

Where HVAC systems are predictable and logical, building occupant needs and weather are equally erratic. To deal with these daily and seasonal vagaries, more water systems employ sophisticated sensors and actuators to reduce use or to match supply and demand better. Outdoors, new weather sensors are one solution for helping rightsize the irrigation system — but the smart systems can be found everywhere, indoors and out. The challenge for project teams is to properly specify the plumbing controls to ensure the ideal water flow levels and proper operation of each fixture.

At points of occupant use, this often means implementing sensor technology to trigger water flow. Sensors generally operate by heat detection (infrared or IR) or motion detection or a combination of both, and each technology has its advantages. While some designers consider them to be standard for restrooms, many studies actually contest the notion that sensor faucets save water when compared to manually operated swivel faucets.

One fixture replacement study by the water consulting firms Veritec Consulting of Ontario, Canada, and Koeller and Company of Yorba Linda, Calif., tracked water consumption in a major commercial office building over a period of two years, replacing manually activated faucets with sensor units. Using an established baseline as a control, the study reported that water consumption increased by 30 percent with sensor-activated faucets3 — and toilet operation by sensor flush was determined to be even more wasteful.

Similarly, a utility study of London’s Millennium Dome included a comparison of IR sensor faucets with manual swivel and push-top faucets. Swivel faucets were found to consume the least water, using about 0.24 gallons of water per washroom visit, while both push-top manual and IR sensor-activated faucets consumed about twice that amount.4

Faucets with push-tops or IR or motion sensors face one main challenge: actuator timing, which may range from five to 12 seconds. “Have you ever held your hands under a running faucet for 12 seconds? You get bored and waste water,” asks Gunnar Hubbard, AIA, principal of the green-building consulting firm Fore Solutions of Portland, Maine, which was acquired in January by engineering conglomerate Thornton Tomasetti. Hubbard contends that users only need two or three seconds to wet or rinse hands. Another issue: Even when sensor actuators are correctly timed, they may backfire if not adequately maintained. For instance, a low battery may mean that the sensor fails to trigger the actuator — merely annoying if it won’t turn on but terribly wasteful if it fails to cut the flow off.

On the subject of batteries for sensor faucets, an important recent advance is the hydro-powered sensor technology that has become commercially available in recent years. This makes use of the energy of the water flow itself, from toilet or sink plumbing, to recharge the battery that powers the sensor. “Hydro-powered sensors make a difference,” remarks Susann Geithner, LEED AP O+M, BD+C, director of sustainability with HSB Architects + Engineers, Cleveland. “They reduce consumption of resources and are easy to use for retrofit applications.” Others are less enthused about the technology, noting that while they reduce maintenance requirements, they do not have any impact on water use.5

Sensor-operated fixtures do have their place and their contribution to make. “We are still fans of these controls” in spite of the drawbacks, says Pauline Souza, AIA, LEED AP BD+C, director of sustainability with WRNS Studio, a San Francisco-based architecture and planning firm. “We find that most people will connect their inclusion to water-saving goals — meaning it changes behavior, which is good.”

SMMA’s Dion adds that public health and operational goals may be served by the technology: “Sensors do make a difference by providing the secondary benefits of being low maintenance and more hygienic.”

Go with the Flow

Experts suggest that the best water-conservation approaches often rely on the simplest flow-control devices. A 0.5-gallons-per-minute (gpm) low-flow aerator performs well, requiring only a simple installation to meet the strictest requirements for point-of-use control. For an office restroom or kitchenette, the 0.5 gpm can save 77 percent more water and energy than a standard 2.2 gpm aerator, or as much as 20,000 gallons annually.6

Even better, some say, are laminar-flow devices because the flow feels “heavier” compared to the softer feel generated by an aerator, which adds air to the water. The end-user may perceive the laminar device’s flow as a higher flow rate, even though both produce a 0.5 gpm flow.7

As for faucet and flush controls, other options exist, and some of them are distinctly low-tech. For those who wish to specify touchless washrooms, pedal-operated fixtures are available for toilets and sinks; this option eliminates the problems with sensor-driven actuators while delivering a hygienic, low-maintenance solution as part of a successful water efficiency strategy. A novel technology now being used in Europe could be brought to bear to create efficient solutions in North America, says Dion: “These are faucets that allow for ultra-low flow and more depending on how much force you apply to the handle. So, people normally only open them to the ultra-low-flow position.” These mechanical controls use resistance to discourage the user from opting for heavier flow.

For larger commercial projects, the design team should also consider water-flow controls on the macro level, rather than only considering points of direct use and consumption. “Water-flow controls can be of use for a couple of reasons,” says Group Mackenzie’s Mitchell. “They can detect higher-than-anticipated water use in systems, which may lead to the proper diagnosis of an operations or maintenance issue requiring system recalibration.”

Similar to the European resistance faucets, “Water-flow controls can also create a higher level of awareness of water use throughout the facility, which can lead to occupants improving the monitoring of their water use,” Mitchell adds.

The Net-Zero Gardener

Awareness of water use is growing in high-profile applications such as lawn irrigation systems at corporate headquarters that actuate during a string of rainy days. The owner’s “reduce and reuse” mantra already has many in sustainable design working toward the goal of a net-zero-energy building — ZEBs, in industry parlance. But is it possible to design a net-zero water project? Not only is it achievable, say experts, but many project teams have adopted the standard as their main goal.

The process of achieving net-zero water for new construction projects goes beyond the walls of the facility, beginning with a full site assessment and predevelopment hydrology, says SMMA’s Dion. This big-picture includes awareness of both site conditions as well as regional conditions as well. According to the EPA, site hydrology includes understanding runoff, infiltration, and evapotranspiration rates and volumes typical of a natural site before construction-related land disturbance.

Water used in landscaping and irrigation is no small part of a facility’s overall consumption. According to the U.S. Geological Survey, 30 percent of daily water consumption in the United States (close to 8 billion gallons)8  is dedicated to outdoor use. The majority of that is for landscaping, notes Paul Kephart, president of Rana Creek Design, an ecological design firm based in Monterrey, Calif. For that reason, he says, “We need to design our landscapes and water use around two principles,” specifically:

1) Zero potable water for nonpotable uses.

2) Zero potable water for landscape irrigation.

“Typically we have more water than we need when we practice these simple guidelines,” Kephart adds.

The biggest, thirstiest culprits are expansive, manicured grounds. Even an average-sized suburban lawn consumes 10,000 gallons of water each year, not including incidental rainwater, according to Amy Vickers’s Handbook of Water Use and Conservation (Waterplow Press). “Why do we have to have such large lawns?” asks HSB’s Geithner, prompted by her experience working in Europe. “And why is it a problem if it goes a bit yellow in the summer?”

Alternatives to traditional irrigation and to common landscaping approaches are a part of the solution, say environmental design advocates. According to WRNS Studio’s Souza, many clients are open to alternatives such as selecting native and drought-tolerant plantings. Yet some end-users prove resistant: “Higher education campuses have a difficulty moving away from lawns,” she says.

Xeriscape and Irrigation Control

Many project teams take on the responsibility of urging their clients in water-saving directions for landscaping, generally tending toward the ideal of xeriscape, a landscape with reduced or zero need for supplemental water from irrigation. Two factors contribute to the success of xeriscape: Plantings appropriate to the local climate and techniques for minimizing evaporation and run-off. “In many cases, we design for no irrigation other than the plants’ first-year establishment needs,” says Dion. “This is attractive to clients as it provides the benefits of low maintenance and reduced operations costs.”

Adding to the design priorities for best-practice xeriscaping, Group Mackenzie’s Jenny Richmond, ASLA, LEED AP, recommends focusing on demand reduction first, including:

• Soil preparation
• Use of native or adapted species
• Clustering and placement of plantings to consolidate water needs
• Limited use of lawns
• Effective maintenance and operations programs

For these steps to work, she adds, project teams must communicate their intent to the client, starting in the design phase and continuing through post-occupancy. “Education is critical,” says Neil Rosen, AIA, LEED AP, director of Sustainable Development for the North Shore LIJ Health System, Bellmore, N.Y., a large U.S. nonprofit healthcare provider. “If the people utilizing the landscaping systems think that they are not working correctly, they will override them and obviate all your good work.”

As for site technologies to support water conservation, a few proven components should be considered. “Rain sensors are an absolute must, and soil moisture sensors are a great idea if installed correctly,” Rosen advises. These wireless and hardwired devices contain hygroscopic disks that swell in the presence of water to activate switches controlling automatic irrigation systems; they may be combined with freeze sensors. In states from Minnesota to Florida, rain sensors are required by law.

Used by her firm at the new Sunriver Aquatic Center in Sunriver, Ore., “High-efficiency irrigation heads are widely available and work well,” says Richmond. The firm also recommends irrigation control systems with weather-driven program capabilities that also tie into the rain and soil moisture sensors. This strategy has also been used at higher education projects, such as Oregon State University’s Student Legacy Park.

According to Richmond, the $18.9 million Aquatic Center’s irrigation rain-bypass allows for seasonal adjustment, with daily weather-based scheduling handled by advanced sensors that calculate evapotranspiration (ET) and measure sunlight and temperature. The ET value determines the correct seasonal adjustment percentage value to send to the irrigation controller, determining its run time. The operators boast of water savings amounting to 30 to 50 percent better than hose for traditional irrigation practices.

While practitioners agree on these benefits, there are areas of contention, too. For example, drip irrigation is controversial, with some believing that while installation is relatively expensive, money can be saved over the long run. Other green-building experts insist that the technology can be impractical and expensive to maintain over time, preferring to limit the amount of irrigation needed instead.

The best conservation techniques may be those found in the planning and post-occupancy phases. Commissioning is increasingly common for site installations where irrigation systems are used, Dion notes, because it provides best assessment for potential reduction goals. Where full commissioning is not undertaken, a basic punchlist or audit can serve similar purposes. “The project audit covers site inspection, performance testing and irrigation scheduling to achieve maximum benefit,” says Richmond. “Regardless of the system or technology, if it is not operating properly potential efficiencies are lost — and water and energy usage may even increase.”

Plumbing and Project Strategy

For most facilities, indoor plumbing is where the rubber meets the road on water conservation. Occupants use most water as individuals, which means that the technology associated with occupant access to water, not to mention occupant behaviors, will determine the effectiveness of water efficiency measures.

Fixture type is a crucial decision: For example, EPA figures suggest that a single-family home with three residents can reduce water consumption by 54,000 gallons annually using water-efficient plumbing fixtures.9 Installing low-flow showerheads alone can reduce annual consumption by 20,000 gallons for a family of four.10

This decision is especially important for certain retrofit projects where the only opportunity to save water may be at points of use. “We do a lot of interior projects in existing buildings, which are all about using ultra-low-flow, automatic fixtures that also save energy for hot water generation,” says HSB’s Geithner. “Reuse or collection is often not possible without expensive and extensive retrofits.”

Plumbing technology and fixture types must be specified with facility type and tenant behaviors in mind, Rosen advises: “It’s most important to equip a facility with fixtures that have the most appropriate efficiency for the intended usage. This may not be the most efficient fixture available.” As an example, Rosen suggests low-flow fixtures in utility sinks used to fill mop buckets will save no water at all but only hamper and annoy the end-users. This mindset was applied to the health system’s first LEED Platinum certification: a third-floor renovation at the Katz Women’s Hospital at North Shore. “By specifying and installing the appropriate flow and flush fixtures we were able to achieve a 51 percent reduction in our water usage,” Rosen recalls.

Geithner agrees, adding that, “Going high-tech might backfire: You have to consider the people factor. For instance, if the facility has many visitors, you need to consider that visitors don’t take time to learn how a faucet or toilet works. In an office, people use the same restroom every day, and they can learn a little bit.”

Specifying properly also demands careful research that goes beyond the manufacturer’s provided information. “Some low-flow toilets are very effective at conveying waste with a single flush, while others with the same advertised efficiency require two or three flushes,” notes Group Mackenzie’s Wieland. “Any real world reductions with this fixture are eliminated regardless of the calculated savings.” That two fixtures with the same rated efficiency could perform so differently seems counterintuitive, but it’s a common challenge.

Another surprisingly contrary example comes from waterless urinals. Pint-flush urinals are frequently an effective choice, notes SMMA’s Dion: “They offer easier maintenance than the waterless type, and we find our clients and their facilities managers are more comfortable with them.” Rosen concurs, adding that one-pint models are easier to maintain than waterless, and save nearly as much water.

Other plumbing and fixture technologies match expectations for no-nonsense performance and efficiency. With few exceptions, low-flow faucets come recommended for commercial and institutional restroom applications. “Sensor-type low-flow fixtures are our standard,” says Dion, except for specific facility types, such as corrections, where required specialty fixtures still aren’t offered in low-flow models.

For interior retrofit projects, Geithner refers to her team’s focus on ultra-low-flow automatic fixtures, which also save energy for hot water generation. “When using low-flow fixtures in a retrofit situation, however, you have to be very careful with travel distance of the hot water, and the selection and setup of the hot water heater,” she explains.

Expert Advice

Most experts interviewed for this education article agree, however, that regardless of their efficiencies plumbing fixtures will never do the job by themselves.

“It is critical for a client to know how water-efficient systems should be maintained and operated,” says Rich Mitchell, AIA, LEED BD+C, managing principal with Group Mackenzie. “Otherwise, the water systems designed for the facility will never perform as expected or intended. This level of communication must go beyond the key stakeholders in the room when the building is designed and extend to the building occupants to be effective.”

Fortunately, the LEED certification family provides for a number of best-practice considerations and benchmarks for project design and implementation. Points for water-efficiency techniques include reducing by half or eliminating entirely the use of potable water in irrigation, as well as achieving a significant reduction in wastewater, either by recycling it or treating it onsite. Credit points for water-efficient indoor fixtures reward targeted use reductions of 20 percent or 30 percent from a calculated baseline. Similar credits are for such programs as LEED for Schools, Retail, Commercial Interiors and also LEED-EB for retrofits of existing buildings.

Many professionals would argue that LEED credits for water conservation are readily achievable, even easy, to include in any project. Making them work as intended, on the other hand, is the big challenge. And it’s a challenge worth rising to, they add.

Says Rana Creek Design’s Kephart, “Let’s not kid ourselves: Water is the most precious of resources.”

Give Them a Sign: Managing Occupant Water Habits

Project team experience in designing and constructing water-efficient buildings demonstrates the power of individual behavior to support — or undermine — facility features.

Take the hospitality industry: Recent research by a team at Virginia Tech found that about 60 percent of respondents conserve water at home, but less than 40 percent do so at a hotel.11 Similar behaviors can be expected at the workplace and in schools, for example.

“You will have to make the water consumer responsible for their consumption,” says Susann Geithner, LEED AP O+M, BD+C, director of sustainability with HSB Architects + Engineers, Cleveland.

Education of the users and facility managers is key, adds Neil Rosen, AIA, LEED AP, director of Sustainable Development for the North Shore LIJ Health System, Bellmore, N.Y. “With appropriate education, there is a possibility that behavioral change can occur,” he says. “If you can achieve that, you’ve won the battle.”

Connecting the dots between waste and cost is one tactic. “That’s when you get people to care,” says Geithner, who suggests metering and billing for water consumption per unit, per office space, per equipment — whatever it takes to drive the point home to individuals, departments and/or tenants. “Then they will report the constantly running toilet and welcome aerators to reduce water flow.”

But the best and most consistent way to reach occupants and visitors may be signage.

“Signage is a silent reminder every time someone uses a break room sink or toilet room fixture,” says Martine Dion, AIA, LEED AP BD+C, a senior associate and director of sustainable design at SMMA, Cambridge, Mass. Signs can let occupants know that the building or organization is conserving and why, says Rosen. One approach is to use temporary signs highlighting water savings, such as gallons per minute (gpm) tied to dollars or quantities saved.

Even more advanced strategies — such as monthly and annual benchmarking of facility water consumption, and comparisons against established goals — can be employed.

Rosen suggests creating a “conservation competition” between facilities or departments, an approach that not only raises user awareness but also valuable user rivalries.

The Hidden Costs of Free Water

While rain and greywater at first look like free sources of water for other building uses, there are important costs to consider.

First, there’s the first cost of installing the proper systems to allow capture and storage of stormwater and effluents from sinks and showers.

In the operations phase, incoming water is continually treated, filtered and disinfected for reuse — typically for toilet flushing and subsurface irrigation. The processes require maintenance and, in some cases, chemical or light treatment. Four basic steps are typically included:

•             Settling
•             Aerobic pretreatment
•             Multi-stage filtration, including reverse osmosis
•             Ozone and ultraviolet light disinfection

A typical system can produce a gallon of purified, nonpotable water per minute, at a cost of less than a penny — that’s for operation only.

That’s a pretty good deal, depending on the installed costs of water conservation systems.

Quiz

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