Last year, I outlined the updates introduced in the 2025 revision of ASSE 1086, Performance Requirements for Reverse Osmosis Water Efficiency – Drinking Water. In 2026, the standard will undergo an additional, smaller revision prompted by an EPA request to incorporate language consistent with the WaterSense program. This article summarizes the upcoming changes, reviews the revisions made in 2025, and explains the steps listees must take to transition from ASSE 1086 2022 to the 2025 and forthcoming 2026 editions.
Reverse osmosis (RO) systems are effective at removing a wide range of contaminants but are historically among the least water efficient treatment technologies. Many systems return less than 20% of input water as treated water, largely due to the rinse water required for proper membrane function. ASSE 1086 was created to support water conservation by establishing efficiency targets for RO system design.
Since ASSE 1086 was first published in 2020, the EPA WaterSense program released its Specification for Point of Use Reverse Osmosis Systems, Version 1.0. Under this specification, performance testing must follow ASSE 1086. WaterSense now requires a minimum efficiency of 30%, reduced from the 40% previously required in ASSE 1086-2022. ASSE 1086 has been updated accordingly.
To comply with ASSE 1086-2025 and the WaterSense specification, systems must meet the following requirements:
- Achieve at least 75% total dissolved solids (TDS) reduction each day
- Maintain an average recovery of at least 30% over 20 days, with no result below 23%
- Retain at least 50% of the Day 1 flow rate throughout testing
Additionally, systems must comply with NSF/ANSI Standard 58, Reverse Osmosis Drinking Water Treatment Systems, achieve a minimum 30% efficiency, and demonstrate resistance to premature membrane plugging — an issue commonly associated with higher efficiency designs.
The 2026 revision will require manufacturers to include a statement indicating the following: “This system has a [XX] percent efficiency rating in the production of treated water. Efficiency rating means the percentage of the water going into the system that is available to the user as RO treated water. This means that the system will send [YY gallons or liters] of water down the drain for every [gallon or liter] of treated water it produces.”
Products currently listed to the 2022 edition will require retesting to meet the stricter 2025 requirements. Products already certified to the 2025 revision will not need additional testing. Updating to the 2026 edition will require verification that the mandated efficiency statement has been included.
The goal of ASSE 1086 and WaterSense is to help consumers, jurisdictions, and system designers identify high efficiency RO systems. By preparing early, listees can more easily meet these requirements and streamline the certification process.
For certification inquiries, contact ASSE at staffengineer@asse-plumbing.org. To purchase ASSE 1086, visit assewebstore.com/asse-ansi-1086-2025-download. For questions regarding product certification, contact Christopher White, ASSE senior manager of Product Certification, at chris@asse-plumbing.org.
