Multi-benefits of Onsite Non-potable Water Systems

What’s an “Onsite Non-potable Water System”?

  • Onsite: Placed in a location that varies in size from single-family-residential up to a neighborhood or district (example: Hassalo on 8th NORM system) and even up to a wastewater treatment facility in cases where water is reused close to the facility (example: John Day hydroponic wastewater treatment facility)
  • Non-potable: Not drinkable (but great for many other uses!)
  • Water: That substance that we’re all mostly made of and we can’t live without for more than a few days.
  • System: A collection of treatment, storage, and conveyance hardware and/or software (basically the pipes, tanks, and technology that stores, treats and moves water for our use).

Put all these words together and onsite non-potable water systems include:

  • Rainwater harvesting
  • Condensate harvesting (water from the air)
  • Stormwater harvesting
  • Reuse of water from fixtures without sewage (e.g. sink, tub/shower)
  • Reuse of water from fixtures with sewage (e.g. toilet)
Phipps Botanical Garden (Pittsburgh, PA). Constructed wetlands/lagoon and sand filter treats water from fixutres with and without sewage before additional mechanical treatment. Water is then used for watering orchids.
Photo credit: Paul G. Wiegman

When properly planned, designed, constructed, and maintained, these systems have numerous benefits over conventional “waste” and water treatment systems. Generally, onsite water reuse systems often do two or more of the following:

  • Save and/or generate money
  • Protect public health
  • Preserve instream flows and fish habitat
  • Promote resilience
  • Enhance emergency preparedness
  • Save and/or generate energy

Why is this important?

We shouldn’t be treating water to a standard higher than it is needed for the end use. For instance, we shouldn’t be using drinking water to flush our toilets! This is called “fit-for-purpose” water and we can save a lot of water and energy, which protects environmental quality, makes us more resilient in the face of climate change, and still protects public health.

Choose from the talking points you or your audience is most concerned with. Click here to jump to:

Public Health Benefits
Social Benefits,
Financial Benefits,
Water Quality Benefits,
Water Quantity Benefits,
Other Environmental Benefits,
Resilience Benefits

Public Health Benefits

  • Proper sanitation prevents disease. Water infrastructure was initially developed to protect the public from water-borne diseases. As populations grow and climate change impacts our access to water supplies, demands on our drinking water systems can be alleviated by reusing onsite water for non-potable uses. Non-potable water reuse can reduce domestic water use by up to 60% when applied to non-potable end uses such as irrigation and toilet flushing. Source: US Department of Energy
  • Reduce urban heat island effect. The urban heat island effect increases summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and deaths, and water quality. Increasing vegetation at a variety of canopy levels lowers surface and air temperatures by shading and cooling. To conserve drinking water for health and sanitation needs, non-potable onsite water should be used to irrigate these landscapes. Sources: Purdue University, EPA: Heat Island Effect
  • Free model codes and ordinances are available for under-resourced jurisdictions. Language for onsite non-potable water systems has been developed by health and environmental agencies in 11 states and the District of Columbia for use in other local and/or state programs. It’s now possible to develop permit programs using an internationally-accepted approach that is more protective of public health than current Environmental Protection Agency standards for conventional water systems.  Source: National Blue Ribbon Commission for Onsite Nonpotable Water SystemsSource: Water Environment & Reuse Foundation (WE&RF)

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Social Benefits

  • Equitably provide a means of self-reliance. Smaller systems with a lower upfront cost would be easier to finance compared to massive investments in centralized water and wastewater infrastructure, making communal ownership an option. Onsite water systems generate a water supply that may be sold to pay off the systems and generate a profit for those communities, if desired.
  • Generate good-paying green jobs. Jobs in water are already good-paying jobs. Onsite non-potable water systems would be numerous, distributed, and smaller than a single conventional water or wastewater treatment plant, creating more opportunities for planning, design, constructing, and especially maintaining and operating these systems. Dividing maintenance and operation requirements to different levels of expertise can create more entry-level jobs with opportunity to move up through on-the-job training and professional development. This division of tasks would make these systems even more cost-effective to maintain and operate, which is always the biggest cost of infrastructure development. Source: Making the Utility Case for Onsite Non-potable Water Systems
  • Enrich building occupants’ relationship with water. People living in buildings that generate their own water supply tend to be more aware of the water they’re using and what they’re putting in the drains. Onsite non-potable water systems have been shown to create a greater appreciation for water and good habits around conservation and preventing pollution. Source: Puttman Infrastructure tour of Hassalo on 8th
  • Enhance livability. Vegetated onsite water treatment systems are the easiest to maintain with lowest energy demand. “Green infrastructure” like this reduces crime, lowers traffic speeds, gives site users a sense of well-being and more. Source: Green Cities: Good Health
  • Create an opportunity for art. Onsite water systems often have tanks, ponds, and other structures that can be artfully integrated into the landscape and architecture.

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Frick Environmental Center (Pittsburgh, PA). Rainwater floods this installation during storms, mimicking the nearby ravine watersheds. This water is then harvested and treated to non-potable standards, and used to flush toilets and irrigate. When the weather is dry, the space is interactive and explorable.

Financial Benefits

  • Avoid large capital improvement costs and rate hikes. Decentralized systems can be integrated into centralized system infrastructure, avoiding large capital improvement costs that get passed on to ratepayers by reducing the need to expand municipal water and wastewater systems. Source: Environmental Protection Agency
  • Blending water supplies optimizes affordability. Across the United States, onsite water systems are generating a profit. Switching from single or dual water supply to a diversified water portfolio with onsite systems will allow public agencies to integrate these systems into existing infrastructure to optimize cost-savings for ratepayers.
  • The cost to upgrade our existing centralized municipal water infrastructure increases every year. “The total investment gap through 2025 is expected to be $105 billion, and $152 billion, by 2040 if left unaddressed. This doesn’t include replacing more than 7.3 million lead service pipes, which adds at least $30 billion to the investment gap.” Large municipal system use a lot of energy to move massive amounts of water and nutrients across large areas and may not be the most sustainable investment. Investing in the current infrastructure will be more expensive than optimizing our investment across the less expensive and more resilient onsite nonpotable water systems. Source: American Society of Engineers

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Water Quality Benefits

  • Reduce algae blooms and other low flow impacts. Using water more than once leaves more water in the environment to lessen the frequency and impact of low river flows.  (Source: Environmental Protection Agency) Trout Unlimited’s Coastal Streamflow Stewardship Project demonstrates how rainwater harvesting can solve timing problems to reduce draws during low flow periods.
  • Protect nutrient-sensitive waterways. Water reuse has been used to reduce or eliminate wastewater discharges where excess nutrients would impact sensitive waterways. On the other hand, water with high levels of nutrients is beneficial for irrigation, keeping water and nutrients onsite as plants uptake them.
  • Reduce and prevent pollution generally. Stormwater and wastewater reuse lowers the amount of pollution entering a waterway. Where combined sewers are carrying both these waters, combined sewer overflow events occur less often. Source: Environmental Protection Agency

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Water Quantity Benefits

  • Minimize flooding. One type of onsite water system captures rainwater and stores it in a tank for reuse and can reduce flooding. “Active” rainwater harvesting systems, which integrate this water supply with a conventional stormwater runoff detention system (
    which has been used for decades at the site scale to reduce community flooding ) have been found to be even more effective for reducing runoff and promoting a cleaner surface water supply. Source: Environmental Protection Agency
  • Enhance wetlands, groundwater, and surface supply. Reusing water more than once relieves pressure to draw on water from the ground and surface, which are hydrologically connected to each other and to wetlands, too, and influence their ecological health. Source: Environmental Protection Agency
  • Protect watershed health with small-scale approaches. Conventional municipal systems usually draw a lot of water from one watershed and pump and convey it long distances. After people use it, those large volumes of wastewater are conveyed long distances, treated, and discharged to a entirely different watershed. While the downstream may experience beneficial stream restoration, plants and animals in both watersheds can be impacted by downstream flooding and upstream drying out. Onsite water systems can capture, treat, use, reuse, and discharge water all within a small, localized area, much smaller than a watershed. Source: Eco-environmental impact of inter-basin water transfer projects: a review

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The WATER TABLE / WATER GLASS by Buster Simpson at the Ellington Condominiums in Seattle, WA collects rainwater and reuses it for irrigation of the wetland and other courtyard plantings. Photo credit: Maria Cahill

Other Environmental Benefits

  • Reduce energy demand. At over 8 pounds per gallon, water is heavy. Any time water must be pumped (which occurs in almost every system at some point) energy demands increase. Onsite water systems usually convey and pump water over much shorter distances than conventional municipal systems. Source: Environmental Protection Agency
  • Minimize fire damage to buildings. Increasing vegetation, like planting more trees, is an effective approach to restore local and global climate regulation. Wetter soils are cooler soils and both help slow the spread of and intensity of fires, and irrigating with non-potable water is a prudent use of water supplies that can aid establishing vegetation, especially in drought-stricken areas where it may be illegal to water landscapes. Source: United States Department of Agriculture, Forest Service
  • Reduce resources used in the treatment process. Conventional water systems treat all water to the same level of quality, whether we’re drinking it or flushing toilets with it.  Instead of treating all water to a single drinkable standard, onsite waters can be treated to a level that considers their end use and disposal point (e.g. water draining to a municipal wastewater treatment plant versus irrigation), which is also known as “fit for purpose” water.

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Resilience Benefits

  • Diversify a community’s water portfolio. Many places purchase or receive water from outside of their own jurisdiction. Non-potable onsite water reuse systems provide a local, alternate water supply. Source: Environmental Protection Agency
  • Improve emergency preparedness. Onsite non-potable water systems often include smaller, distributed storage ponds and tanks to support a more resilient and robust infrastructure. Additionally, when water is harvested from a roof, reliance on buried pipes are avoided, making continuous water access more likely in widespread fire and earthquake events.  

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Bullitt Center (Seattle, WA), rainwater to potable system.