Building Water Use
Buildings are significant users of the Earth’s freshwater supply. The goal of a responsible building operator should be to encourage a smarter use of water, both inside and outside the facility.
Net Zero Water
Net Zero Water refers to the concept of balancing water demand with water availability. The goal is to achieve a state where the amount of water used is equal to the amount of water replenished or restored, resulting in a net zero water balance1. To achieve this balance, take the following actions.
Minimize Total Water Consumption
Reducing indoor water usage can be achieved by using high-efficiency plumbing fixtures, fittings, appliances and equipment for heating and cooling the building. For outdoor water conservation, the focus should be on water-wise landscaping through xeriscaping and efficient irrigation practices, such as drip irrigation. By using less potable water, a building can also reduce the energy required to transport, treat, and redistribute the water, resulting in cost savings. This is known as the "water-energy nexus." Innovative water efficiency solutions should not only focus on reducing potable water usage, but also reducing the use of non-potable water from alternative water sources where appropriate, like flushing toilets and irrigating landscapes. For guidance on water conservation, see:
- Water Whole Building Systems
- Planted Roof Systems
- Restrooms
- Cleaning Stations
- Landscaping Services
- Plumbing Products
Maximize Alternative Water Sources
Alternative water sources are those that draw water from processes or applications other than freshwater sources like surface or groundwater. Examples of alternative water sources include greywater, reclaimed wastewater, stormwater, rainwater, air handling unit condensate, process equipment discharge water, and drainage or sump water. Depending on their filtration and treatment requirements, alternative water sources can be used for various purposes, such as laundry services, landscape irrigation, toilet flushing, cooling tower makeup water, fire sprinkler systems, and decorative water features. By replacing potable water with alternative water sources, buildings can reduce stress on freshwater sources and make progress toward achieving Net Zero Water goals. To learn more about GSA activities related to water reuse, please refer to:
- GSA Water Reuse Interagency Working Group resource(s) (Coming Soon)
Return Water to Original Source
Every effort should be made to return water used in buildings to the same water source from which it was taken. Water sources may be surface water, such as creeks, streams, or rivers, or groundwater, such as aquifers. Returning water discharged from buildings to its original source, through onsite green infrastructure, prevents the depletion of local watersheds. To achieve Net Zero Water, this extraction and replenishment is measured over the course of a year.
For more information, see DOE FEMP's Federal New Buildings Handbook for Net Zero Energy, Water, and Waste.
1 Department of Energy | Net Zero Water Building Strategies
Related Topics
Aerator for Faucets
Faucet aerators are flow restriction devices designed to reduce the amount of water that comes out of a faucet by mixing air into the water stream. Standard faucet flow rate is 2.2 gallon per minute (gpm). High efficiency aerator flow rate ranges from 1.5 to 0.5 gpm, offering significant water and energy savings.
EPA | WaterSense at Work - Faucets
DOE FEMP | Best Management Practices - Faucets and Showerheads
Alternative Water Source
Alternative water sources are those that draw water from processes or applications other than freshwater sources like surface or groundwater. Examples of alternative water sources include greywater, reclaimed wastewater, stormwater, rainwater, air handling unit condensate, process equipment discharge water, and drainage or sump water. Depending on their filtration and treatment requirements, alternative water sources can be used for various purposes, such as laundry services, landscape irrigation, toilet flushing, cooling tower makeup water, fire sprinkler systems, and decorative water features. By replacing potable water with alternative water sources, buildings can reduce stress on freshwater sources and make progress toward achieving Net Zero Water goals.
DOE FEMP | Best Management Practices - Alternative Water Sources
EPA | WaterSense at Work - Onsite Alternative Water Sources
Blackwater
Blackwater is nonpotable water. Exact definitions for what constitutes blackwater vary, but wastewater from toilets and urinals is always considered blackwater. Water from food preparation areas, shower water, or bathtub water is sometimes considered blackwater, based on state and local laws. Blackwater cannot be used in place of potable water.
Bleedoff/Blowdown
The intentional release of a portion of the recirculating water from a cooling tower or steam system is called bleed off or blowdown. The recirculating water carries dissolved solids, which need to be removed because they can cause mineral buildup inside the system. Blowdown can be minimized through proper water management of the system via chemical treatment and filtration for example.
DOE FEMP | Best Management Practices - Cooling Tower Management
DOE FEMP | Best Management Practices - Steam Boiler Systems
EPA | WaterSense at Work - Cooling Towers
Compost Toilet
A composting toilet is an alternative to a traditional flushing toilet. Composting toilets are not common in commercial buildings; however, they are becoming a more common environmentally preferred option as they use less potable water, if any. Composting toilets use an aerobic process to break down waste by using little or no water. There are two types of composting toilets: self-contained and split units – both designed to prevent fixture odors.
See Waterless/Dry/Nonwater Fixtures.
Condensate Capture
Condensate capture refers to harvesting condensed water on air handling units to be reused in other applications. As cool air passes through air handling units, water condensate can form from humid outside air (similar to water droplets forming on the outside of a cold glass of water on a warm, humid day). Typically this water is diverted into a pan and discharged to a drain. Instead, this condensate can be captured and diverted to be used beneficially in applications such as cooling tower make-up. The condensate is nearly pure water and therefore can be ideal for cooling towers. Condensate capture typically works best in warm, humid climates. See the case study on a condensate capture program performed by the Environmental Protection Agency (EPA).
Cooling Tower
A piece of building equipment which uses water to absorb heat from air-conditioning systems and regulate air temperature in a facility.
DOE FEMP | Best Management Practices - Cooling Tower Management
EPA | WaterSense at Work - Cooling Towers
Dipper Well
A dipper well is a sink-type fixture that provides a constant flow of water to keep food-preparation and serving utensils clean. Dipper wells can have a flow rate between 0.5 to 1.0 gallons per minute. Dipper wells can be retrofitted with flow restrictors to reduce the flow rate. Find more information on dipper wells at the EPA’s WaterSense at Work.
Drip Irrigation
Drip irrigation, also referred to as “micro-irrigation”, delivers water at low pressure directly at the root zone of the plant through flexible tubing and drip emitters. Drip irrigation is very efficient because it minimizes the amount of water lost due to evaporation or overspray, which is common with traditional spray type irrigation equipment.
Alliance for Water Efficiency | Drip and Micro-Spray Irrigation Introduction
Dual-Flush Toilets
A dual-flush toilet is a type of high-efficiency fixture. Dual-flush toilets are those that have two levels of flushing – a higher water use flush (full flush) for solids and a lower water use one (reduced flush) for liquids. The effective flush volume of a dual flush toilet is 1.28 gallons per flush. Dual-flush toilets are available in tank or flush valve types.
Evapotranspiration Controllers/Weather-Based Controllers
Evapotranspiration Controllers, also known as weather-based controllers, use weather data to calculate evapotranspiration (ET), which represents the level of water loss from the soil due to evaporation and plant transpiration. ET is used to determine the irrigation schedule that applies the appropriate amount of irrigatio required by the landscape. These devices, as well as rain sensors and other “smart” irrigation devices, help prevent water waste.
Faucet
A faucet is a valve controlling the release of water, which have standard or high-efficiency rated flow rates. Faucets can be fitted with flow restrictors or aerators to make them more water-efficient.
EPA WaterSense | Bathroom Sink Faucets & Accessories
Flow Restrictor
Flow restrictors are devices designed to limit the amount of water that comes out of a faucet or showerhead. They save water by constraining the flow of water through the fixture, typically by mixing air into the stream of water.
Front-loading Clothes Washer
Also referred to “horizontal axis” clothes washer, this machine uses a drum that is oriented horizontally with access on the front side of the machine (versus on the top of the machine). Front-loading clothes washers use significantly less water, typically 15 gallons per load versus 23 gallons per load for a standard top-loading machine. See ENERGY STAR clothes washers.
Gallons per Cycle (gpc)
Gallons per cycle (gpc) references the amount of water used in a controlled period of flow (the “cycle”) of a fixture such as faucets and washing machines. The cycle can be controlled by either an electronic or mechanical device. The cycle is calculated using the flow rate in gallons per minute (gpm) and the duration setting (in seconds). For example, in a metered (timed) faucet, a flow of 0.5 gallons per minute for 30 seconds would be 0.25 gpc.
Gallons per flush (gpf)
Gallons per flush (gpf) references the amount of water used per flush in flush fixtures, such as toilets and urinals.
Gallons per minute (gpm)
Gallons per minute (gpm) references the amount of water used by a flow fixture in a measured amount of time (one minute).
Greywater
Greywater is the wastewater from showers and sinks. Greywater can be captured and used in place of potable water to flush toilets or irrigate landscapes. Greywater DOES NOT contain water from urinals or toilets.
Guiding Principles for Sustainable Federal Buildings
The Guiding Principles for Sustainable Federal Buildings and Associated Instructions are a set of sustainable principles for integrated design, energy performance, water conservation, indoor environmental quality, materials, and resilience aimed at helping Federal agencies and organizations:
- Reduce the total ownership cost of facilities
- Improve energy efficiency and water conservation
- Provide safe, healthy, and productive built environments
- Promote sustainable environmental stewardship
Guiding Principles for Sustainable Federal Buildings and Associated Instructions
Hardscape
Hardscape is the inanimate elements of the building’s landscaping. For instance sidewalks, plazas, parking lots, and stone walls are all hardscape. Hardscape prevents water from being absorbed into the soil and can contribute to the heat island effect if it is dark in color.
High-Efficiency Faucet
A faucet with a flow rate that does not exceed 1.5 gpm for private settings and 0.5 gpm for public settings.
EPA WaterSense | Bathroom Sink Faucets & Accessories
DOE FEMP | Best Management Practices - Faucets and Showerheads
High-Efficiency Plumbing Fixture
High-efficiency plumbing fixtures use less water than code-compliant, standard plumbing fixtures. The following is a listing of specific high-efficiency fixtures.
- High-Efficiency Faucet
- High-Efficiency Showerhead
- High-Efficiency Toilet (HET)
- High-Efficiency Urinal (HEU)
High-Efficiency Showerhead
A showerhead that does not exceed a flow rate of 2.0 gpm.
DOE FEMP | Best Mangement Practices - Faucets and Showerheads
High-Efficiency Toilet (HET)
A toilet with an effective flush volume that does not exceed 1.28 gpf.
DOE FEMP | Best Management Practices - Toilets and Urinals
High-Efficiency Urinal (HEU)
A urinal that does not exceed 0.125 gallons per flush (1 pint per flush).
DOE FEMP | Best Management Practices - Toilets and Urinals
Lavatory
Lavatory is a term meaning a basin for washing. Essentially, the hand washing basins located within a restroom are called lavatories.
Leak Detection
Leak detection is a process that involves monitoring water distribution systems for leaks to help identify and pin point leak locations so that they can be repaired.
DOE FEMP | Best Management Practices - Distribution System Audits, Leak Detection, and Repair
Low-Flow Fixture
Antiquated term that was used to describe efficient plumbing fixtures after the passage of EPAct 1992. The current industry standard term is “high-efficiency”.
Makeup Water
Water fed into a cooling tower system to replace water lost through evaporation, drift, bleed-off/blowdown, or other causes.
Nonwater/Waterless/Dry Fixtures
A nonwater fixture is a type of high-efficiency fixture. There are nonwater toilets and nonwater urinals, although nonwater urinals are far more common. Nonwater urinals have no flush mechanism. Liquid travels through a gel-filled cartridge which forms a seal designed to prevent odors from escaping. Maintenance involves the replacement of the cartridge after a certain number of uses, specified by the manufacturer. There are various types of nonwater toilets including foam, incinerating and composting - all of which eliminate the need to flush water down the toilet during normal operation.
Pervious
Pervious ground surfaces allow precipitation to percolate through, letting the water be absorbed and naturally filtered by the ground. Pervious surfaces reduce the amount of water that is sent to storm drains. Types of pervious surfaces include landscape, pavers, porous asphalt, and pervious concrete.
Potable water
Potable water is drinkable water. It flows from faucets and showerheads and is used in dishwashers, all of which require clean water for sanitary purposes. Potable water is also used to flush toilets and irrigate landscapes – both are functions that could easily use greywater (recycled water) without compromising efficiency. Where feasible, greywater should be used for these functions.
Pre-Rinse Spray Valve
Pre-rinse spray valves are spray nozzles that are used in commercial kitchens to remove large food scraps from dishes typically prior to being placed in a dishwasher.
EPA | WaterSense at Work - Pre-Rinse Spray Valves
DOE FEMP | Best Management Practices - Commercial Kitchen Equipment
Pressure-Assisted Toilet
A pressure-assisted toilet is a type of high-efficiency fixture. Pressure-assisted toilets use the pressure from the main water line to more efficiently empty the bowl and use less water.
Process Water
Water used for industrial processes and building systems, such as cooling towers, boilers, and chillers. Greywater can sometimes be appropriately used as process water, conserving potable water.
Rainwater Harvesting
Rainwater harvesting captures, stores, and uses rainwater for beneficial uses such as landscape irrigation. Rainwater harvesting typically refers to capturing rainwater that falls onto a roof surface and has not come into contact with the ground. Rain that hits the ground, called stormwater, can easily pick up contaminants such as oil and other pollutants and requires more treatment than rain that is collected from a roof. To get more information on rainwater harvesting, go to the EPA’s WaterSense at Work.
Reclaimed Wastewater
Reclaimed wastewater is wastewater that has been treated to a level that is safe for reuse. The level of treatment determines the potential uses for reclaimed wastewater. Some reclaimed wastewaters are restricted to only non-potable reuse (e.g., irrigating non-public areas), while others are approved for potable reuse, where the water is so pure that it can be introduced directly into a water treatment plant. Reclaimed wastewater is becoming more commonly provided by municipal water suppliers. Some military installations also reclaim wastewater at on-site wastewater treatment plants. To get more information on reclaimed wastewater, see the EPA’s WaterSense at Work.
Showerhead
Showerheads control the speed and pressure of the water flowing from the pipe with standard or high-efficiency rated flow rates.
See High-Efficiency Showerhead
Side Stream Filtration
Side stream filtration continuously filters a portion of recirculating water in a cooling system, removing suspended solids and debris from the water that can lead to less fouling of the system and improves system performance. Find information on side stream filtration on the Federal Energy Management Program’s side stream filtration fact sheet.
Single Pass Cooling/Once Through Cooling
Single pass cooling or once through cooling equipment removes heat from a process or application by circulating water through a heat exchanger only once and is discharged to drain.
EPA | WaterSense at Work - Single-Pass Cooling
DOE FEMP | Best Management Practices - Single-Pass Cooling Equipment
Soil-moisture Sensor
Soil-moisture sensors measure the amount of moisture in the soil. It is typically a probe that is inserted directly into the ground that measures the soil’s conductivity. Conductivity of the soil increases as water content increases. Soil-moisture sensors are used in irrigation controls to help determine the amount of irrigation needed to reach a desired soil moisture content.
Find more information on soil-moisture sensors at the Alliance for Water Efficiency’s website.
Standard Plumbing Fixture
Standard plumbing fixtures are plumbing fixtures that meet the current federal requirements established by the Energy Policy Act (EPAct) of 1992. Standard fixtures meet minimal code requirements.
The following list provides the current standards for plumbing fixtures:
- Toilets: 1.6 gallons per flush (gpf)
- Urinals: 1.0 gpf
- Faucets: 2.2 gpm (at 60 pounds per square inch (psi) operating pressure)
- Showerheads: 2.5 gpm (at 80 psi operating pressure)
Steam Systems
Steam systems generate steam to provide heat for buildings and process needs such as commercial kitchens and manufacturing. Steam boilers produce steam, steam is sent through a distribution network, and often condensed steam is returned back to the boiler, called a condensate return. As water evaporates in the boiler, dissolved solids build up creating scale in the boiler. To reduce scale, contaminated water is released from the boiler, called “blowdown”, and fresh water is replaced, called “make-up”. To get more information on steam systems, go to EPA’s WaterSense at Work.
Toilet
Toilets typically are standard or high-efficiency. Older buildings may have toilets that do not meet the current standards and exceed the standard flush rate of 1.6 gpf. These are typically buildings built before 1994.
Urinal
Urinals typically are standard or high-efficiency. Older buildings may have urinals that do not meet the current standards and exceed the standard flush rate of 1.0 gpf. These are typically buildings built before 1994. Of the high-efficiency types, the most water-efficient is the nonwater type.
Water Closet
Water closet is a term meaning flush toilets.
See Toilet.
Water Conservation
Over 400 billion gallons of water are used every day in the United States. Demand is increasing even though usable supply is decreasing. Civilian agencies in the federal government use 47 billion gallons of water per year, the equivalent of more than 70,000 Olympic-size swimming pools. These agencies could save 7.8–12.3 billion gallons (17–26%) annually just by using simple “off the shelf” water conservation measures, including replacing existing toilets, faucets, and showerheads with more efficient versions.
GSA | Indoor Water Conservation
DOE | Developing a Water Management Plan
DOE | Guidance for the Implementation and Follow-up of Identified Energy and Water Efficiency
DOE | Measures in Covered Facilities
Water Efficiency
Buildings are significant users of the Earth’s freshwater supply. The goal of a responsible building operator should be to encourage a smarter use of water, both inside and outside the facility. Indoor water use reduction is typically achieved through efficient plumbing fixtures, fittings, appliances and process equipment used to heat and cool the building; outdoor water use reduction efforts should focus on water-wise landscaping and efficient irrigation.
Learn more about Water Efficiency.
Water Purification
Water purification is a process where undesired contaminants are removed from a water supply to provide pure water typically when high-quality water is needed such as laboratory and medical applications. Water purification systems include reverse osmosis, deionization, and distillation. To get more information on water purification, go to EPA’s WaterSense at Work.
Water Use Baseline
Estimated or metered water use in a specified year from which water use reductions are expected to occur.
International Association of Plumbing and Mechanical Officials
Xeriscaping/Native Landscaping
Xeriscaping or native landscaping is a type of landscaping method that makes routine irrigation unnecessary. The practice uses water-efficient choices in planting and irrigation design. It incorporates climate-appropriate and native plants to decrease the amount of watering required. The choices will vary depending on the ecosystem and weather patterns of the location. In some locations, xeriscaping means use of drought-tolerant plants; in other, it means the use of wetlands plants. Xeriscaping also uses soil amendments such as compost and mulch to reduce evaporation of water.
University of Missouri Extension | Water-Efficient Gardening and Landscaping
EPA WaterSense | Water-Smart Landscapes Start With WaterSense
EPA | WaterSense at Work - Landscaping
DOE FEMP | Best Management Practices - Water-Efficient Landscaping
