Water Efficiency (Building)
Using less potable water in buildings through fixtures, systems, and reuse.
Quick Answer
Building water efficiency is the practice of reducing potable water use in a building and its site. Typical strategies include low-flow and WaterSense-labeled fixtures, efficient irrigation and cooling systems, leak detection, and reuse of graywater or harvested rainwater for non-potable needs such as toilet flushing and landscaping.
The Full Picture
Water efficiency matters because buildings consume large volumes of potable water and generate wastewater that must be treated, and water and sewer costs are rising in many regions. Lower consumption reduces operating cost, supply stress, and the energy used to pump, heat, and treat water.
The usual approach follows a hierarchy. First reduce demand with efficient fixtures, such as WaterSense-labeled toilets, urinals, and faucets, efficient appliances, and smart irrigation. Then reduce losses through metering, submetering, and leak detection. Finally substitute alternate sources, such as rainwater, condensate from air handlers, or treated graywater, for uses that do not need drinking-quality water.
The details are heavily regulated. Alternate water systems require plumbing code compliance and often local health department approval, with dual piping, labeling, and backflow protection. Landscape choices, such as native plantings and drip irrigation, often cut the largest share of outdoor use. Cooling towers are another significant load in commercial buildings.
Efficiency measures have tradeoffs. Very low-flow fixtures can cause drain-line carry problems in long horizontal runs, and reuse systems add maintenance. Good projects set a baseline and target, verify performance with meters after occupancy, and plan operations for the systems. Poor projects specify reuse systems that no one is trained to maintain.
Real Examples
Common Misconceptions
People assume: Water efficiency is only about low-flow fixtures.
Actually: Fixtures are the easy part. Irrigation, cooling towers, process loads, leaks, and alternate water sources often account for more savings in commercial buildings.
People assume: Graywater and rainwater reuse is simple to add to any project.
Actually: These systems need dual plumbing, treatment, signage, and local approvals, plus ongoing maintenance. Rules vary by jurisdiction, so involve the authority having jurisdiction early.
Frequently Asked Questions
What is water efficiency in buildings?
It is reducing potable water consumption through efficient fixtures and equipment, leak control, smart irrigation, and the use of alternate water sources where allowed.
What is WaterSense?
WaterSense is an EPA program that labels products, such as toilets, faucets, and irrigation controllers, that meet water-efficiency and performance criteria.
What is the difference between graywater and rainwater?
Graywater is used water from sinks, showers, and laundry, excluding toilets and kitchen sinks. Rainwater is precipitation collected from roofs. Both can serve non-potable uses when treated and permitted.
Who pays for water efficiency measures?
Owners typically fund them as capital cost, then recover savings through lower water and sewer bills. Payback varies by local rates and building type.