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 was developed to aid water conservation efforts by providing manufacturers with an efficiency target for their RO system designs.
Traditional ROs are known to be one of the least efficient treatment products in the market. This is due to the fact that of all of the water that enters into the system only a small percentage is returned to the user as drinkable. In fact, for traditional RO systems, 3 gallons of water go to the drain as waste for every gallon produced as treated water. Being mindful of the need for more sustainable systems, manufacturers of RO systems have been working to improve the efficiencies by reducing the amount of rinse water needed to operate the devices.
As is often the case when making changes to complicated designs, tradeoffs exist that affect other aspects of the design’s performance. As efficiencies in the system improve, there can be a reduction in the life of the membrane. The manipulations made to RO systems that result in increased efficiency can often cause the membrane to foul. Fouled membranes no longer produce significant amounts of purified water. This leads to the membranes needing to be replaced much more frequently. Replacing membranes more often can lead to customer dissatisfaction due to the increased cost of operation.
It became clear that there was a need to have standards and specifications covering water efficiency for residential RO systems that included performance testing to address the membrane life concerns of high-efficiency RO systems. ASSE 1086, Performance Requirements for Reverse Osmosis Water Efficiency – Drinking Water, was developed and focuses on the environmentally friendly aspect of the treatment technology while also ensuring that efficiency is not compromising membrane life.
Additionally, the U.S. EPA WaterSense program developed an efficiency specification, WaterSense Specification for Point of Use Reverse Osmosis Systems, Version 1.0 (published in 2024). The WaterSense specification requires testing to be in accordance with ASSE 1086. The pass/fail criteria within the WaterSense specification is 30% efficiency as opposed to that in previous ASSE 1086-2022, which was 40% efficiency. Since the publication of the WaterSense specification, the ASSE 1086 standard has been revised to match the WaterSense requirements.
There are other standards that are also relevant to the performance of reverse osmosis treatment devices. Most notable is — NSF/ANSI 58, Reverse Osmosis Drinking Water Treatment Systems. Note that compliance with NSF 58 is a requirement of ASSE 1086-2025 and the EPA WaterSense specification.
The ASSE 1086 standard includes test requirements for complete systems or components, including system manifolds, RO membranes, pre- and post-filtration assemblies, supply and drain connections. It focuses on three main requirements:
- As mentioned before, the system must be compliant with NSF 58.
- The product must meet a minimum efficiency rating when tested in accordance with the NSF/ANSI Standard 58. Note, the NSF 58 standard is not an efficiency standard. While the testing protocol is present, there are no minimum requirements to meet with respect to efficiency. This is where ASSE 1086 comes in, requiring the RO device to be at least 30% efficient.
- To ensure membranes continue to function for long periods of time, a membrane life test was developed. It is an accelerated 20-day test that simulates one year use of an RO membrane.
Other performance aspects evaluated by ASSE 1086 include the verification of the reliability of the system’s automatic shut-off valve and a flow restrictor tolerance test. These two attributes were included because they can also have an effect on efficiency.
ASSE 1086 certification, along with the EPA WaterSense mark, is a valuable tool for helping consumers make informed decisions about purchasing a reverse osmosis treatment system. It provides the peace of mind knowing that the published efficiency has been verified and the product has been evaluated to rigorous performance requirements.
