Indoor Efficiency, Outdoor Irrigation, Leakage, Rainwater and Stormwater Management, and Local Water Reuse

Technical Brief — September 7, 2026
Qizhong (George) Guo, Ph.D., P.E., BC.WRE
Professor, Civil and Environmental Engineering
Rutgers University–New Brunswick

On August 26, 2026, TIME published “We Asked Experts For the Easiest Ways to Shrink Your Home Water Usage,” which included interviews with me and two other university professors. The article prompted me to look more closely at the numbers behind household water conservation and to place everyday conservation practices in a broader water-systems context.

Indoor Efficiency Has Improved Dramatically

One encouraging finding is how much indoor water efficiency has improved. The Water Research Foundation’s 2026 Residential End Uses of Water study reports average single-family indoor use of about 38.5 gallons per person per day, down 44.4% from 69.3 gallons in 1999. More efficient toilets, clothes washers, showerheads, faucets, and dishwashers have played a major role.

At the same time, the commonly cited U.S. household-use figure of about 82 gallons per person per day includes both indoor and outdoor use and comes from an older national dataset. The two figures therefore should not be directly subtracted to estimate current outdoor consumption.

Water Losses Occur from the Home to the Public System

Significant opportunities remain. Household leaks collectively waste large quantities of water, although losses vary greatly from home to home. Beyond the house, leaking service lines and aging public water systems form another major source of loss.

These problems must be addressed at very different scales—from replacing an inexpensive toilet flapper, to repairing an underground service line, to renewing major water mains—but they are complementary parts of the same conservation challenge. Household conservation cannot substitute for maintaining the infrastructure that captures, treats, pumps, and delivers drinking water.

Outdoor Water Use Depends Strongly on Climate and Landscape

Outdoor use is much more dependent on climate and season than indoor use. Nationally, roughly 30% of residential water use occurs outdoors, while the share can become much higher during hot or dry conditions.

Conservation can come not only from watering less, but from watering according to actual plant needs, accounting for recent rainfall, irrigating when evaporative losses are lower, maintaining irrigation equipment, using better controls, reducing unnecessary turf, and selecting native or climate-adapted vegetation.

Landscape choice matters. Turf can be retained where it serves recreation, gathering, play, or erosion-control functions, while less intensively irrigated vegetation may be appropriate where lawn is primarily ornamental. The potential savings, however, are highly climate-dependent and should not be transferred uncritically from arid regions to humid climates such as New Jersey.

Rainwater and Stormwater Can Be Managed as Local Resources

Rainfall itself is also a substantial resource. One inch of rain on 1,000 square feet of roof represents about 623 gallons of water, while the same storm over a 2,000-square-foot roof represents about 1,247 gallons before collection losses.

A household need not be limited to a single rain barrel. Multiple barrels can serve different downspouts or be connected together, and detached garages, sheds, or other roofed structures may provide additional collection areas where gutters and downspouts are available. Two conventional 55-gallon barrels provide 110 gallons of storage, four provide 220 gallons, and six provide 330 gallons. Even several barrels, however, may capture only part of the runoff from a substantial storm, and storage must be used or emptied between storms to regain capacity.

Rain barrels and cisterns can directly substitute captured rainwater for potable irrigation water. Downspout disconnection, rain gardens, landscaped infiltration areas, and other green-infrastructure practices can also retain, infiltrate, and manage stormwater close to where it falls.

Rain gardens provide an especially useful connection between water conservation and stormwater management. When established rain gardens replace irrigated turf, they can reduce the need for potable irrigation water. At the same time, where a stormwater utility offers credits, a properly designed and maintained rain garden may qualify for a partial stormwater-fee credit. These are two distinct benefits: one comes from reducing metered water use, while the other comes from reducing or managing runoff onsite.

A less explored possibility is foundation-drainage or sump-pump water, which may sometimes provide another nonpotable source for irrigation. Its availability, water quality, timing, storage requirements, pumping energy, and economics deserve further research rather than being assumed beneficial everywhere.

The Financial Value of Conservation Depends on Rate Structure

A conserved gallon does not necessarily have the same financial value everywhere. Indoor conservation can often reduce both water and sewer costs and, where hot water is involved, energy costs as well. Outdoor irrigation savings may reduce only the water bill where sewer charges are flat or based on winter water use.

Appendix A of the full brief compares two New Jersey communities to illustrate this quantitatively. The same reduction in indoor water use can produce substantially different household savings because one community charges a flat residential sewer fee while another uses a volumetric, winter-based sewer formula.

Stormwater utilities introduce a third household cost signal. Unlike potable-water and sewer bills, stormwater fees are generally related to runoff contribution or impervious area rather than gallons of water consumed. New Brunswick became the first municipality in New Jersey to establish a stormwater utility in 2024, following state enabling legislation enacted in 2019. Its program also provides for credits for qualifying onsite stormwater-management measures.

From Household Conservation to Water-System Resilience

Household water conservation is therefore more than a collection of isolated tips. It operates at several connected scales:

  • Inside the home: use efficient fixtures and appliances and eliminate leaks.
  • Outside the home: irrigate efficiently and choose landscapes suited to local climate and function.
  • At the property scale: capture, retain, infiltrate, and reuse rainwater and other suitable local nonpotable sources.
  • At the community scale: reduce losses from service lines and aging distribution infrastructure and provide sustainable funding for water and stormwater systems.

The broader lesson is simple:

Use potable water efficiently. Eliminate avoidable losses. Choose landscapes suited to local climate and need. Match water quality to the intended use. Retain and reuse local water where practical. And maintain the infrastructure that delivers the water in the first place.

**Read the full technical brief (PDF)

**Read the full technical brief (PDF) — Chinese Translation of the English Version (中文翻译版)

Related: TIME, “We Asked Experts For the Easiest Ways to Shrink Your Home Water Usage”, August 26, 2026.