AIA Course: High-Efficiency Plumbing Systems for Commercial and Institutional Buildings
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With drought conditions sweeping across many parts of the United States and more than a billion people lacking access to safe drinking water worldwide, demand for better building-based water efficiency and capture is soaring. The National Oceanographic and Atmospheric Administration reported in March 2011 that more than a quarter of the U.S. was experiencing moderate to extreme drought, and 36 states predicted significant water shortages until at least 2013.
Water represents the third-largest global industry, which is why water conservation continues to make headlines around the world. Water supply, cleanliness, and conservation are of growing concern to environmental and professional associations.
In developed countries, demand is largely driven by daily household and business use. The average American family of four uses up to 400 gallons of water every day, according to the U.S. Environmental Protection Agency. This staggering consumption scenario has put the issue of water conservation high on the agenda of building owners and their Building Teams. Fortunately, plumbing product manufacturers are diligently responding with ever-improving water-efficiency technologies and products.
LOW-FLOW, AND GOING LOWER
Whether it’s the latest low-flow toilet technology, approaching rates of just 1.1 gallons per flush (gpf), faucets as low as 0.25 gpm, or showerheads flowing at 0.5 gpm, plumbing product manufacturers continue pushing for new fixtures and systems that save even more water than before.
After reading this article, you should be able to:
+ DISCUSS new developments in low-flow and sensor-operated plumbing fixtures and their relationship to environmental improvement and occupant well-being.
+ LIST the comparative environmental and health benefits and shortcomings of rainwater harvesting systems.
+ EXPLAIN how concerns related to health and safety affect the design and implementation of graywater reuse systems.
+ DESCRIBE software tools and new environmental codes and standards that affect the selection, specification, and design of commercial plumbing systems and their health, safety, and welfare benefits for building occupants.
At the same time, some experts are concerned that it’s taking some time to work out the kinks in the impact of low-flow fixtures on overall building plumbing systems. The issue dates back to the original EPA mandate in 1992, which reduced toilet gpf levels from 3.0 to 1.6, a 47% reduction. “The first wave of ‘1.6-ers’ did not function well at all, with widespread reports that you had to flush at least twice to evacuate the bowl,” recalls David E. DeBord, CPD, LEED BD+C, ARCSA-AP, a Chicago-based plumbing and fire-protection engineer. “It appears that the products were rushed to market without sufficient research and development, and it took four to five generations for these fixtures to develop into the highly efficient units that we know today.”
So, while many MEP/FP consultants like DeBord are pleased with the enhanced levels of engineering expertise going into the design of new low-flow fixtures and systems, concerns regarding a few plumbing-related issues remain.
“Lower flow rates can increase the amount of time it takes for hot water to reach the fixture,” notes Keith W. Seier PE, CPD, vice president with MEP engineering firm Environmental Systems Design, Chicago. “Smaller openings and restrictors can cause mineral deposits to clog the faucet, and some shower valves may not operate correctly with low flow rates.” Seier also points out that design considerations must be given to the problem of “drain line carry,” the phrase used to describe having enough waste water to push waste through the sewer line. Not having sufficient drain line carry could require additional waste stacks, thus potentially having a major impact on infrastructure design.
With regard to hot water flow, John Rattenbury, PE, LEED AP, an associate in the plumbing and fire-protection group at MEP firm R.G. Vanderweil Engineers, Boston, explains that while the plumbing code allows for uncirculated hot water branches to be as far as 100 feet away from the fixtures, there may not be sufficient hot water in the supply pipe; this leads to the “hot-water waiting situation” that Seier alludes to. “Therefore, it has become necessary to circulate the hot water supply to within a foot or so of the faucet, meaning that the circulated mains must be extended to the wet wall behind the faucets,” notes Rattenbury, a member of the American Society of Plumbing Engineers (ASPE).
Similar questions linger about waterless urinals. The jury is still out as to whether the water savings from waterless urinals outweigh the all-too-common consequences of operations personnel not following special cleaning requirements. This can lead to crystallization and pipe blockage, says David C. Smith, PE, plumbing and fire protection department manager with Bala Consulting Engineers, King of Prussia, Pa. Consequently, some specifiers favor 0.125 gpf or 0.25 gpf urinals over waterless urinals, except in situations where the facilities staff is fully trained in maintaining the waterless units.
Despite these concerns, DeBord, an adjunct assistant professor at the Illinois Institute of Technology and a member of the International Association of Plumbing & Mechanical Officials (IAPMO), the International Code Council, and ASPE national committees, still sees flow rates as continuing to go down. He predicts that eventually floor-mounted, bottom-outlet, pressure-assisted tank-type toilets will flush at less than 1.0 gpf. While there are already some water closets on the market utilizing vacuum-assist technology that are advertised as using only 0.8 gpf, they are not generally used in commercial installations, namely because the floor-mounted surfaces and corners are hard to clean.
“I think that we will see these fixtures evolve into something more acceptable to the world of owners, users, and officials,” says DeBord. “Bottom-outlet offers a higher level of flushing efficiency because they get more of a boost from gravity. This will save water, use smaller water pipes, and have lower pressure requirements, which will reduce pumping power.”
STILL WORK TO BE DONE ON SENSOR-OPERATED FIXTURES
Another oversight in the race to go green has been that Building Teams occasionally lose track of the cost/benefit analysis, says Peter A. Kraut, PE, president of South Coast Engineering Group, Calabasas, Calif. Kraut, a designer of more than 50 LEED-accredited buildings, a past president of ASPE’s Los Angeles chapter, and a member of the California Plumbing and Mechanical Contractors Association, says he is impressed with such advances as pressure-compensating aerators and microturbines, which can be used in lieu of batteries on sensor faucets. Yet he questions whether the environmental footprint of microturbine manufacturing and maintenance actually exceeds that for producing and installing a couple of AA batteries every year.
Kraut notes, too, that with flow rates continuing to decrease, there may be a point at which users will look for ways to defeat the safeguards of sensor faucets. He points out that, to wash one’s hands and rinse off the soap, as the flow rates decrease, the duration of water use must increase; moreover, as the shut-off comes more quickly, the number of uses will rise. So how much water will be saved?
Other plumbing experts question how far technology can go in saving water when matched against human intervention. “Plumbing fixtures do not conserve water; people do,” quips Joe Scott, CPD, FASPE, LEED AP, a vice president with the St. Louis office of Cannon Design.
It would seem, then, that Building Teams must understand the greater context and demographics of where activated faucets will be used. Public facilities are a popular application, primarily for personal hygiene purposes as opposed to infection control, claims Scott, a former ASPE national president with 30 years of plumbing engineering experience. Bala’s David Smith believes that sensor-operated faucets do save water; he also believes that solar- and hydro-powered units can save energy. On the other hand, sensor-operated flush valves don’t always conserve water because low-flow fixtures sometimes fail to clean the bowl with a single flush.
And while plumbing engineers are impressed with how far sensor-based technologies have come, accuracy and performance can still be lacking. For example, sensor manufacturers have struggled to make the devices work properly when users wear dark clothing, or under decorative lighting fixtures or low-lighting conditions. This being the case, DeBord prefers products that require users to wave their hand over the top of the toilet to trigger flushing. This way the unit is still touchless, but the technology works more predictably.
RAINWATER HARVESTING: REACHING A NEW HIGH-WATER MARK
With drought conditions often catching municipalities by surprise, many public officials are looking at ways to entice wider use of rainwater capture. A few jurisdictions—for example, Santa Fe County, N.M., and Tucson, Ariz.—have implemented laws requiring rainwater harvesting or retention on site.
Rainwater harvesting systems are becoming more and more prevalent in commercial projects. “I see few factors standing in the way, and in fact, it has become practically a necessity or prerequisite to incorporate some form of rainwater harvesting system for new construction in many areas of the country,” confirms R.G. Vanderweil’s Rattenbury.
While a lack of codes and standards has served as a deterrent in the past, this has changed as organizations like ASPE and the International Association of Plumbing and Mechanical Officials now provide valuable guidelines and standards in an attempt to eventually incorporate the technology into the plumbing codes. ASPE is currently working with the American Rainwater Catchment Systems Association on an ANSI-accredited standard, expected to be released soon, and one that can be deployed internationally. The standard will be known as ARCSA/ASPE Rainwater Catchment Systems Design and Installation Standard #63.
Meanwhile, engineers and product developers are learning and refining harvesting techniques as related to such critical functions as collection, storage, filtration, and disinfection. Many of these strategies are being picked up from European designers and manufacturers who tend to have more years of experience with the technology, according to Rattenbury.
For example, siphonic roof drainage works well when the water must be carried over long distances. Essentially, the technology moves the water along at a faster velocity, as compared to a conventional gravity system, although it does have to be slowed prior to discharging into the collecting tank.
DeBord debunks the myth that rainwater harvesting depletes the groundwater supply; in fact, he says, the opposite is actually true, as the more gradual release of water into the ground, following its use, is more replenishing to the groundwater. “Much of the rain in our built environments does not have an opportunity to soak into the ground because so much of the ground is covered with concrete and pavement,” he says. “This leads to increased erosion, which increases sediment in the rivers, interfering with the natural hydrologic cycle on a multitude of levels.”
Furthermore, rainwater harvesting can often provide a good return on investment under certain conditions, such as in situations where ample collection surfaces are available, or where sizable loads, such as irrigation or cooling water, can use supplementary water sources.
Climate can also be a determining factor. Regions with intermittent rainfall are the most ideal fit for rainwater harvesting techniques. In drought-prone areas, however, the cost of a system can quickly outweigh its usefulness due to the extremely large tanks that are needed to store the water for long periods of time. These tanks require a very high level of treatment—and resulting cost—for filtering and disinfecting the stored water.
ON-SITE GRAYWATER: WAITING FOR THE RIGHT REGULATIONS
As noted in Building Design+Construction’s 2009 White Paper, “Green Buildings + Water Performance” water-efficient fixtures will only take water conservation so far, to about a 20-30% total reduction. Achieving greater reduction levels approaching 40% or better will likely require water reuse techniques, including the recycling of graywater from bathroom sinks, showers, and washing machines.
Defined as wastewater with relatively low chemical, geological, and solids loading, graywater can, in some jurisdictions, be directly used as irrigation without any treatment. With some minor processing, graywater can be used to flush toilets and to handle other nonpotable applications. However, the catch is that many health departments remain wary of graywater, and the industry has yet to develop codes and standards to help regulate and guide its use.
Graywater systems are much more common overseas than in the U.S., because many areas outside the U.S. lack the municipal infrastructure to treat water, say experts. On the other hand, “The United States has the infrastructure to collect storm and sanitary water from the buildings and residential areas,” notes Environmental Systems Design’s Seier, who serves on the Chicago ASPE chapter’s board of directors. “But unfortunately the infrastructure is aging and becoming overtaxed in many large cities. When infrastructure starts to fail, city officials and building owners will be forced to look at graywater and blackwater solutions.” (Blackwater is water that has been mixed with toilet waste.) Yet the first cost for the systems is relatively high due to the complexity and sophistication of the water treatment equipment. Rattenbury further notes that the energy output required to treat the water can, in some cases, exceed the benefits of conserving water.
Meanwhile, the technology continues to advance, with recent developments in packed-bed aeration and microdosing, which are greatly improving the purity of the effluent, according to Kraut. “Add these to UV light sterilization, and there is no reason that graywater systems could not be used in toilet reflush. I think the administrative authorities recognize this as the next logical step in protecting our natural resources, and I believe we will see movement on this front very soon.”
Already on the household-level market are small graywater systems, which install with direct connections to individual fixtures or appliances, such as showers, baths, sinks, sink-toilet combinations, and laundry facilities. At one extreme is a system that utilizes a 15,000-gallon, high-density polyethylene tank that outputs water for irrigation, while at the other end is a system that uses a 5.5-gallon tank, installed right beneath the bathroom sink, to collect used sink water, sanitize it, store it, and then utilize it to flush a nearby toilet.
Another interesting area of development is with more localized products known as upflush macerating pump systems. While these systems do not provide reusable water, they are useful for applications where conventional plumbing is either not practical or not available. With a powerful grinder, these systems can take care of waste from the toilet and other fixtures, such as sinks, bathtubs, and showers.
Similarly, vacuum plumbing systems—commonly used in prisons, cruise ships, and airplanes—suck the contents from the bowl, requiring as little as 0.25 gpf, although they do draw power. In locations were water storage is limited, they can be a good solution.
PLUMBING DESIGN TOOLS: BRINGING BIM TO THE JOB SITE
With the increasing efficiency levels of technology and plumbing products, design and specification has become even more critical, encouraging plumbing engineers to better consider how plumbing design tools can enhance their designs.
For instance, MEP building information modeling programs now include such features as tagging piping, equipment, and components in three-dimensional views. They also allow Building Teams to create more user-friendly systems, and some offer a parallel pipes design tool. Novel plumbing specification information systems such as ATS Spec are also valuable in providing Revit content, building specifications, and building product schedules for the whole Building Team, adds Seier. However, he says he’s still waiting for the industry to develop a software program that calculates water efficiencies effectively.
Kraut, too, warns against getting too caught up in the software revolution. “The best design tool available to any plumbing engineer is education,” he says. “The most dangerous thing is the uneducated designer with a fancy software package. I have not yet found software that sufficiently checks conditions for each application, and I have seen many, many technologies misapplied.”
While Scott sees BIM as moving in the right direction, he cautions that it cannot replace the professional’s ability to actually engineer a proper and efficient plumbing system. While BIM can be used effectively as a documentation tool and to better understand space allocations and other system requirements, it currently lacks certain information and user input. “We need better information as it relates to water efficiencies and usage, as much of the information we are using is very old and dates back to before the current water-conservation period,” he notes. “There has not been an extensive amount of research to determine how much water we are using currently.”
DeBord cites the need for studies to collect real-world data, which will help better define how people are actually using fixtures. This information would help the industry more accurately define baselines to better gauge water reduction and efficiency calculations.
CODES AND STANDARDS KEEP PUMPING UP THE ACTION
While much work remains to be done on codes and standards for graywater and rainwater harvesting, an active base of associations, municipalities, model code developers, and green rating systems is diligently addressing the issue of water conservation. For example, the International Plumbing Code, the Universal Plumbing Code, and the National Plumbing Code are all currently addressing these and other water use matters. Similarly, ASHRAE is currently working on a standard in conjunction with ASPE, the American Water Works Association, and the U.S. Green Building Council that includes water conservation.
The 2010 IAPMO Green Plumbing and Mechanical Code Supplement, a separate document from the Uniform Plumbing and Mechanical Codes, establishes requirements for green building and water efficiency applicable to plumbing, mechanical, and solar energy (both hydronic and photovoltaic) systems. The Green Supplement serves as an adjunct to the Uniform Codes or any of the plumbing and mechanical codes used in the U.S.
At the local level, California and Texas are taking the lead with separate mandates that all new toilets sold or installed after 2014 be high-efficiency—meaning no more than 1.3 gpf, dual-flush, or composting. Seier also anticipates that such a federal standard won’t be too long in coming.
Another interesting development is LEED’s new water-efficiency credit for cooling towers, which engineers are predicting could have a major effect on water conservation. “Cooling tower make-up is generally the largest domestic water load during the cooling season, so depending on the size of the building, this credit could account for the largest overall water savings,” says Seier.
While Smith expects the new credit to reduce cooling tower blowdown, he questions how cost effective the additional monitoring of condenser water, makeup water, and nonpotable water used for cooling towers will be. “The cost of nonpotable water treatment will determine the advantage of this credit,” he says.
Engineers also anticipate LEED certification requirements to continue becoming more restrictive, particularly in the realm of water use. DeBord encourages designers to look beyond the codes and realize that reducing the quantity of water used for fixtures can only go so far, at which point there may be the need for a paradigm shift in the way the public thinks of water, he says.
Such a change, DeBord says, might be to impose a surcharge on monthly water bills when a prescribed quantity per person is exceeded. “This is not going to fly right now, but at some point, it will become necessary to preserve our species,” he says. +