Buildings are significant users of 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 balance.1 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 additional guidance on water conservation, see the water overview and planted roof pages.
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.
Water reuse regulations
Water reuse may be regulated at the state or local level. EPA’s Regulations and End-Use Specifications Explorer or REUSExplorer tool links to summaries of state water reuse regulations or guidelines and is searchable by source of water and end-use application.
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 Federal New Buildings Handbook for Net Zero Energy, Water, and Waste [PDF].
U.S. General Services Administration