Water is one of our most precious natural resources. We're accustomed to having clean, reliable drinking water provided to our buildings by our municipalities. We depend on it. For many regions across the United States, water is in short supply. According to the U.S. Environmental Protection Agency (EPA), a recent government survey indicates that at least 36 states are anticipating local, regional, or statewide water shortages by 2013. These statistics underscore our need to manage resources better at every level.
So, what can a facility manager do? According to the U.S. Department of Energy (DOE), commercial buildings consume 88 percent of the potable water in the United States. Facility managers have a unique opportunity to make a huge impact on overall U.S. water consumption. Benchmarking your facility's water use and implementing measures to improve overall efficiency will help you on your mission.
Water Use in Buildings
Water use in commercial buildings varies with plumbing-fixture type, the kind of equipment installed, and the function of the building. For example, buildings that have commercial kitchens and cafeterias have higher process water consumption rates than those that do not. Similarly, buildings that operate hydronic cooling systems also have higher process water consumption rates.
While these systems may consume their share of water, they're not the majority users. Instead, that honor belongs to restroom plumbing fixtures: lavatories, water closets, urinals, and showers. The U.S. DOE estimates that restroom plumbing fixtures account for approximately 60 percent of the total water use in office and administrative buildings; the remaining 40 percent is estimated to be used by heating and cooling systems. According to a study performed by the Boston-based Massachusetts Water Resources Authority, plumbing fixtures account for approximately 47 percent of commercial building water use, with cooling systems and kitchens trailing at 34 percent and 14 percent, respectively.
With restroom fixtures accounting for the majority of commercial building water consumption, the best opportunities for increasing efficiency are found there. The good news is that higher-efficiency plumbing fixtures are becoming more widely available.
Before 1992, plumbing fixtures consumed at least three times the amount consumed by current fixtures (see Comparison of Plumbing Fixture Water-Flow Rates below). After the passing of the U.S. Energy Policy Act of 1992, which promoted the conservation and efficient use of energy and water, strict requirements for water-fixture performance were put in place. In recent years, through codes and an increasing awareness of our need to utilize natural resources efficiently, further strides have been made in increasing water efficiency. The current Intl. Plumbing Code (IPC) and Uniform Plumbing Code (UPC) are both more restrictive than the Energy Policy Act of 1992; however, it doesn't stop there. Local communities, utility companies, and groups, such as the U.S. Green Building Council (USGBC), are pushing the envelope to encourage even bigger increases in water efficiency. To meet these demands, several manufacturers have introduced innovative technologies to further reduce the water use of fixtures to well below code requirements.
Common Plumbing Fixtures
A quick summary of the typical plumbing fixtures found in a commercial/institutional building includes:
- Water closets. In commercial buildings, most water closets have valves that utilize water-line pressure to meter out a set volume of water. Current valves provide flush volumes of 1.6 gallons per flush (gpf); their older counterparts provide more than double that flow.
Urinals. Similar to water closets, urinals in commercial buildings typically utilize water-line pressure valves. Current valves provide flush volumes of 1 gallon per flush (gpf); their older counterparts may provide more than twice that amount.
Sinks and lavatories. Sinks, such as those in break rooms, often do not have flow-restricting aerators installed. At a minimum, aerators restricting flow to 2.5 gpm should be installed. Lavatories, especially older installations, often have flow restrictors installed that are rated well above the current 0.5 gpm maximum requirement.
Showerheads. Current showerheads are now restricted to 2.5 gpm. For older, compliant showerhead models, the flow stream was not always very effective. More current models provide a steady stream that has a much better delivery.
Calculating a Water-Use Baseline
When evaluating your building's water-use efficiency, the USGBC offers a helpful method that allows you to benchmark annual water use and compare that use to current standards. First, water use is established based on past annual-use records or on estimates of building occupancy. Then, a theoretical water-use baseline is estimated based on the types of fixtures in the building and the number of building occupants. For LEED projects, USGBC standards require a reduction in the fixtures and fittings' potable water usage to a level equal to or below the LEED-EB O&M baseline water usage. The baseline is calculated assuming that 100 percent of the building's indoor plumbing fixtures comply with the requirement of the 2006 Uniform Plumbing Code or the 2006 Intl. Plumbing Code fixture and fitting performance requirements.
For buildings with plumbing systems installed after 1994, the baseline is calculated as 120 percent of the water usage that would result if all fixtures and fittings complied with 2006 plumbing codes. For buildings with plumbing systems installed prior to 1994, the baseline is calculated as 160 percent of the water usage that would result from 2006 code-compliant fixtures and fittings. Once the baseline has been established for the building, the actual use can be compared and measures can be implemented to reduce water use and increase overall water efficiency. This baseline methodology is specific to LEED; however, it can be used in buildings that are not seeking LEED certification.
Tracking Water Use
In order for a facility to become more water efficient, it's important to understand how water is being used. First, identify the key use types: restrooms, cafeterias, cooling tower make-up, or other processes. Installing sub-meters and monitoring these areas will allow the facility manager to have a better understanding of water usage. This will also allow building engineers to more easily identify trouble areas and problems within the building's systems. By evaluating and determining how various systems use water, projects can be implemented to effectively reduce water use.
Ways to Increase Water Efficiency
There are many ways to increase water efficiency in buildings—primarily through plumbing-fixture replacement and implementing new technologies:
Replace older, high-flow water closets and flush valves with models that meet current UPC and IPC requirements. While current codes require the lower flow rate for new fixtures, existing buildings often have older, high-flow flush valves. Despite the tremendous water savings available by updating the fixtures, facility managers often avoid the upgrade due to concerns about clogging. When the Energy Policy Act of 1992 was first enacted, many facility managers experienced problems with the low-flow fixtures clogging due to fixture-design issues. Those problems have long since been addressed and no longer present a problem.
Utilize dual-flush valves on water closets. Dual-flush valves provide a full 1.6-gpf flush and an optional 0.8-gpf half flush.
Consider replacing existing plumbing fixtures with high-efficiency fixtures that exceed UPC and IPC requirements. High-efficiency water closets use 1.3 gpf or less. In most cases, fixtures and valves will need to be replaced to ensure proper operation of the fixture and reduce the chance of clogging. High-efficiency urinals use as little as 1 pint of water per flush, or less than 10 percent of current low-flow models. Before installing these fixtures, it's recommended that the drainage piping be cleaned to ensure proper drainage flow. Waterless urinals don't use water, but instead use a specially formulated liquid to maintain the trap seal. Careful consideration should be given to style and placement before installation. In addition, since these fixtures do not use water, maintenance staff must be specifically trained in the proper cleaning procedures. Ultra-low-flow showerheads typically use 1.5 gpm of water or less. While ultra-low-flow showerheads allow for significant water savings when compared to code-compliant models, they don't always receive high marks from users.
Install or replace existing lavatory and sink aerators with more restrictive aerators. Significant savings can be achieved by replacing 2.2-gpm aerators with 0.5-gpm aerators.
Use alternative water sources. Some jurisdictions have installed (or are planning to install) greywater distribution systems. The water is considered non-potable, but is suitable for use in water closets and urinals. Use of greywater can considerably reduce consumption of domestic water.
The Federal Energy Management Program offers useful tools for estimating and improving water efficiency. Its online calculator estimates the 10-year life-cycle cost of water closets and urinals in comparison with current code-compliant models. The life-cycle cost can then be compared to the cost of replacement to determine the benefit of replacing fixtures.
Facility managers have a unique opportunity to dramatically impact water use in existing buildings. By measuring and monitoring water use, evaluating plumbing-fixture types, and implementing simple water-saving measures, you can easily improve your overall water efficiency.
Comparison of Plumbing Fixture Water-Flow Rates
||Current Plumbing Codes
||4 to 7 gpf
||3.5 to 5 gpf
||5 to 7 gpm
||4.5 to 8 gpm
SOURCE: DOMESTIC WATER CONSERVATION TECHNOLOGIES, FEDERAL ENERGY MANAGEMENT PROGRAM, U.S. DEPARTMENT OF ENERGY, OFFICE OF ENERGY EFFICIENCY AND RENEWABLE ENERGY, NATIONAL RENEWABLE ENERGY LABORATORY, OCTOBER 2002
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Laurie Gilmer is a mechanical engineer at Washington, D.C.-based Facility Engineering Associates (FEA), a national consulting firm focusing on extending the life of, and making improvements to, existing facilities. Gregory Hughel is a staff engineer at FEA.