Reverse osmosis (RO) systems help to eliminate a wide spectrum of harmful contaminates from water. Historically, however, ROs have shown to be one of the least efficient water treatment options. It is not uncommon for an RO device to have a return on water of less than 20%, especially for end users. The reason for this is that in order to function properly, RO systems need a certain amount of “rinse water,” which is typically sent to the drain. This is why ASSE 1086, Performance Requirements for Reverse Osmosis Water Efficiency – Drinking Water, was developed to aid water conservation efforts by providing manufacturers with an efficiency target for their RO system designs.
Since ASSE 1086 was first published, the U.S. EPA’s WaterSense Program has developed water efficiency specifications for RO systems, WaterSense Specification for Point of Use Reverse Osmosis Systems, Version 1.0. Within the WaterSense Specification, the performance requirements shall be tested in accordance with ASSE 1086. The pass/fail criteria within the WaterSense specification is 30% efficiency as opposed to the previous ASSE 1086-2022, which was 40% efficiency. Consequently, the ASSE 1086 standard has been revised to match the requirements of WaterSense.
Below is a summary of the test requirements for a system to be compliant with ASSE 1086-2025 and the WaterSense specification:
- The percent total dissolved solids (TDS) reduction shall be at least 75% each day.
- The system recovery shall be on average a minimum of 30% efficient determined over 20 days. At no time shall the efficiency be less than 23%.
- The flow rate shall not decrease by more than 50% of the Day 1 value throughout the test.
The be listed to ASSE 1086, an RO system must meet all the requirements of NSF/ANSI Standard 58, Reverse Osmosis Drinking Water Treatment Systems, which focuses on the reduction of chemicals typically reduced through a reverse osmosis system. Next, the system must meet a minimum efficiency of 30% return on water. Finally, the RO system must show the ability to avoid premature membrane plugging often associated with higher efficiency systems.
The goal of ASSE 1086 and WaterSense is to help higher efficiency systems be recognized so that water-conscious homeowners, jurisdictions, and plumbing system designers can easily recognize and select these products.
To have your product certified to ASSE 1086, please contact ASSE International at staffengineer@asse-plumbing.org. To purchase a copy of ASSE 1086, please visit https://assewebstore.com/asse-ansi-1086-2025-download/.
For questions regarding certification to the standard, contact Christopher White, ASSE senior manager of Product Certification and Standards, at chris.white@asse-plumbing.org.
