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Is reverse osmosis wasteful?

While RO systems can improve water quality, these systems can also generate a significant amount of water waste to operate. For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced.

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A point-of-use reverse osmosis (RO) system is a water filtration device that is connected to a single fixture (e.g., under the kitchen sink) and uses the process of RO to remove contaminants from the water supplied to that fixture. RO is the process by which pressure forces water through a semi-permeable membrane, creating a stream of treated water, called “permeate,” and a stream of reject water called “concentrate” or “brine.” These systems can potentially remove water contaminants such as lead, volatile organic compounds (VOCs), PFAS, arsenic, bacteria, and viruses. Point-of-use RO systems are typically installed in residential settings but can also be found in commercial office spaces or kitchens.

Why a Specification?

While RO systems can improve water quality, these systems can also generate a significant amount of water waste to operate. For example, a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of permeate produced. Some inefficient units will generate up to 10 gallons of reject water for every gallon of permeate produced. In recent years, membrane technology has improved and some point-of-use RO systems have been designed to operate more efficiently, with some manufacturers advertising a 1:1 ratio of permeate to concentrate production, meaning only one gallon of reject water is generated for each gallon of treated water. Because there is a range of water efficiencies represented within the RO system market, EPA believes these systems could be a suitable product category for WaterSense labeling. As with all WaterSense labeled products, an RO system that bears the WaterSense label would be required to meet prescribed performance standards (e.g., minimum contaminant removal rates) to ensure the product performs as well or better than typical, less efficient RO systems. There are no current federal requirements that regulate the water efficiency of point-of-use RO systems. Due to the water-intensive nature of RO, WaterSense does not intend to promote the installation of RO systems for all applications or encourage their use over other water treatment technologies that do not waste as much water (e.g., filtration systems). However, WaterSense recognizes that RO systems might be appropriate in certain applications, depending on the user’s desired water quality, characteristics of the incoming water supply, and consumer perception and preferences. In these instances, WaterSense intends to help consumers identify and purchase more water-efficient models, thereby contributing to water and cost savings for users. WaterSense estimates that replacing a typical point-of-use RO system with a more efficient system can save approximately 3,200 gallons of water per household per year.

Draft Specification

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EPA released a draft specification for WaterSense labeled point-of-use RO systems on December 1, 2022. EPA is also sharing its draft product notification template for point-of-use RO systems. When EPA releases a final specification for RO systems, licensed certifying bodies will be required to submit information regarding WaterSense labeled RO systems to EPA using this template: EPA will accept written comments and plans to hold a public meeting to discuss stakeholder comments. This public meeting will be held virtually via Zoom on Thursday, January 12, 2023, from 2:00 to 4:00 p.m. Eastern Time (ET). Please register to attend the webinar. All interested parties are welcome to comment on the proposed requirements in the draft specification, as well as the product notification template, until February 3, 2023. Please send any comments or suggestions to watersense-products@erg.com. Please review the instructions on the cover letter if you are submitting any data that needs to be handled as confidential business information (CBI). All comments, except data claimed as CBI, become part of the public record. To facilitate the consistency and usefulness of comments received, please submit your comments using the Template for Public Comment Submission (docx) . You can either download and save this document template and directly insert your comments, or attach your comments in your own document, provided that you clearly reference the text/section in question, your recommended changes, and why you think these changes are needed.

Notice of Intent

In January 2022, EPA issued a Notice of Intent (NOI) to develop a WaterSense specification for point-of-use RO systems to reduce water waste and recognize the most efficient technologies available. In developing a potential specification, EPA’s goal is to encourage the production of and – where the installation and use of the technology is appropriate – the adoption of more efficient RO systems. On February 16, 2022, EPA hosted a teleconference and webinar with stakeholders to discuss the NOI. Register to view a recording of the webinar. Are you interested in finding out more about the development of a WaterSense specification for RO systems? Please email watersense-products@erg.com to be added to the stakeholder list.

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