Water recycling 101: the most common questions about onsite water reuse, answered.

Water

Water scarcity, aging infrastructure, and rising utility costs are no longer distant problems; they’re reshaping how developers, building owners, and cities think about water. Onsite water reuse is one of the most powerful tools available to address these challenges at the building level. But what exactly is it, how does it work, and is it right for your project? We’re answering the most common questions we hear.

What is the difference between water recycling, water reclamation, and water reuse?

The term “water recycling” is generally used synonymously with “water reclamation” and “water reuse.” Water recycling is a broad, umbrella term that can be applied to the general process of collecting used water, treating it, and putting it back to work in some form. Water reclamation focuses specifically on the treatment phase. It’s the act of taking wastewater (water that has already been used and would otherwise be discharged) and processing it to make it suitable for a beneficial use again. Water reuse is about the application — what you actually do with the reclaimed water after treatment. 

What is onsite water reuse and how is it different from regular water recycling?

Onsite water reuse systems collect, treat, and reuse a building’s wastewater locally, rather than sending it to a centralized municipal treatment facility. 

Wastewater (whether blackwater, greywater, rainwater, stormwater or HVAC condensate) is captured, stored, and treated through an advanced multi-step biomimic process that typically includes membrane filtration, UV treatment, and chlorine disinfection. Once treated, the reclaimed water is recirculated back into the building for non-drinking uses such as toilet flushing, irrigation, clothes washing, and cooling towers.

The key difference from conventional recycling? It happens right where the water is used. This creates a decentralized, circular approach in which a building or campus becomes self-sufficient in managing its own water supply. 

What is greywater and blackwater, and which can be reused?

Not all wastewater is created equal. Greywater (also called “gray water”) refers to wastewater from sinks, showers, bathtubs, and clothes washers. Blackwater refers to all wastewater including from toilets and urinals, which requires more advanced treatment due to potential higher pathogen levels. Rainwater, stormwater, and HVAC condensate are additional alternative water sources that can also be collected and reused.

All of these types of wastewater can be safely treated and reused onsite, though the type of system, treatment requirements, and permitted end uses vary by jurisdiction. In many cities, greywater systems are a simpler first step, while blackwater systems capture a larger share of a building’s total water flows and offer higher reuse and savings potential. 

Source: Onsite Non-potable Water Reuse Practice Guide, William J. Worthen Foundation

Learn more about the differences between greywater and blackwater reuse systems.

 

What’s the difference between DPR and IPR?

Both Direct Potable Reuse (DPR) and Indirect Potable Reuse (IPR) are methods of treating wastewater to drinking-water standards, but the key distinction lies in what happens before the water reaches your tap.

With IPR, treated wastewater is first introduced into an environmental buffer, such as a groundwater aquifer, river, or surface water reservoir. The water is held there and mixes with natural sources for a period of time, where it undergoes natural filtration and dilution, before being extracted and treated again to meet drinking water standards. This environmental buffer has made IPR a widely accepted form of potable reuse, with successful implementations across the U.S. for over 50 years.

DPR skips the environmental buffer entirely. Highly purified recycled water is introduced directly into a municipal water supply system or upstream of a drinking water treatment facility. Because there is no intermediate environmental step, DPR relies on advanced treatment technology and continuous water quality monitoring. It is generally more cost-efficient, with one study finding a hypothetical DPR system costs roughly half as much to build as an equivalent IPR system, and produces a smaller carbon footprint due to shorter pumping distances. 

It’s worth noting that both DPR and IPR are distinct from the onsite reuse that Epic Cleantec specializes in. As regulations evolve and public familiarity with water reuse grows, DPR is gaining traction. California passed its DPR regulation in 2024, and as Epic Cleantec’s team has noted: as California goes, so goes the nation.

 

Is recycled water safe to use inside a building?

Yes. When properly designed, operated, and regulated, onsite water reuse systems produce water that is safe for its intended purpose. 

The treatment process, which combines ultrafiltration membranes, UV disinfection, and chlorine,  removes pathogens and contaminants, producing a highly purified output. In fact, the treated water meets disinfected tertiary reuse effluent standards. 

By design and regulatory requirement, cross-contamination between the domestic water supply and the recycled water supply is prohibited, and in many jurisdictions, full-building testing is required periodically to verify that no cross-connection has occurred.

How much water can an onsite reuse system actually save?

The savings are significant. 

Onsite water reuse can account for between 50 and 95 percent of the water used in residential or commercial buildings, depending on the system type and building characteristics. At Epic Cleantec, our OneWater^TM system is designed to recycle up to 95% of a building’s wastewater.

Real-world examples underscore the impact:

• The Salesforce Tower in San Francisco treats 30,000 gallons of wastewater per day, saving over 10 million gallons of water annually, equivalent to the yearly water use of 16,000 residents, and saves an estimated $395,000 in utility costs.

• Kuilei Place, a planned 43-story luxury residential tower in Honolulu, HI, will use Epic Cleantec’s OneWater^TM system to recycle up to 30,000 gallons of greywater per day for toilet flushing and irrigation across its 1,005 units. The system is projected to conserve roughly 11 million gallons of potable water per year and save an estimated $133,000 in utility costs annually. It will be one of Hawaii’s first onsite residential greywater reuse systems. 

What are the financial benefits for building owners?

Water reuse isn’t just an environmental play; it’s an increasingly strong economic one.

U.S. water and sewer rates have surged more than 50% over the last decade, with annual increases of 5–20% in many regions. Los Angeles and Honolulu will see 106% and 115% cumulative sewer rate increases by 2030, respectively. These costs are felt most acutely by large building owners. Onsite water reuse insulates buildings from those escalating costs.

For large buildings over 100,000 square feet, onsite water reuse can save building owners an average of 30–50% — or anywhere from $50,000 to $1 million annually — on water and sewer-related expenses. Additional savings can come from reduced connection and impact fees at the time of construction, as well as energy savings through wastewater heat recovery.

Are there regulations requiring onsite water reuse?

In a growing number of cities, yes, and momentum is building nationally. 

San Francisco was a pioneer, adopting a Non-Potable Water Ordinance (Article 12C) that requires new development projects of 100,000 gross square feet or more to install and operate an onsite water reuse system. This initiative is projected to save 1.3 million gallons of potable water per day in the city by 2040. Los Angeles has similarly mandated that new large residential buildings source 100% of their cooling tower makeup water from non-potable sources, while new construction must reduce overall potable water use by 20%. 

Cities like Austin, Seattle, Denver, Honolulu, and New York are also rolling out their own regulations and incentives. At the federal level, California has now passed Direct Potable Reuse (DPR) regulations allowing treated wastewater to be reused for drinking, effective October 2024.

Check out Epic Cleantec’s list of onsite reuse regulations by state here. 

Is onsite water reuse only for large buildings or new construction?

Not entirely, but new construction is the best fit. 

Installing a reclaimed water distribution system is far easier and more cost-effective during construction than retrofitting an existing building. That said, systems can be tailored to different scales, from individual buildings to entire districts or campuses. Advances in decentralized treatment technologies and modular systems make it feasible across a wide range of project sizes and types.

Epic Cleantec’s OneWater^TM system, for example, can process flows ranging from 1,000 to 30,000 gallons per day and is designed to occupy just a few parking spaces’ worth of square footage, making it one of the most space-efficient systems available.

Why isn’t onsite water reuse more widely adopted yet?

Awareness is the biggest barrier. 

In an informal poll conducted by Epic Cleantec, 36% of respondents cited a lack of awareness as the main reason water reuse hasn’t been more widely adopted in the United States, more than any other factor, including cost or regulatory complexity.

The “yuck factor” is a perception problem, not a technical one. Wastewater recycling is not a new concept, and modern municipal systems have used similar treatment technology for decades. What’s new is doing it at the building scale, which is unfamiliar to most people. 

 

The U.S. EPA’s research highlights that increasing pressures on water resources from climate change, population growth, and aging infrastructure are driving greater interest in onsite water reuse as a practical solution. 

As regulations expand, technology matures, and more real-world case studies demonstrate financial returns, the conversation is shifting. The question for most building owners and developers is no longer if water reuse will be part of their future; it’s when.

Epic can help guide you through deciding which onsite reuse solution is right for your project. Request a free assessment from Epic Cleantec to understand the water savings potential, ROI, and payback period for your building.

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