Yes. Most residential and commercial RO systems waste significant amounts of water during the filtration process. While exact efficiency varies by model, the majority operate with a 4:1 or 5:1 rejection ratio—meaning:

  • For every gallon of purified water produced,

  • 4 to 5 gallons are discharged as wastewater.

This wastewater contains a higher concentration of contaminants than the original source water because RO membranes trap impurities and flush them out in the reject stream. That concentrated water is then sent down the drain or into the environment.

Key Considerations

  • RO wastewater must be disposed of properly, which can complicate installation and increase overall system costs.

  • In regions with high nitrate levels, drought regulations, or strict wastewater management, RO systems can be difficult or impractical to use.

  • One of our California customers, for example, chose Altitude Water’s AWG instead of RO due to the high volume of nitrate-rich wastewater an RO system would have produced.

Additional Concerns

While RO filters out many contaminants, it is not 100% effective. Certain substances—such as PFAS (forever chemicals), VOCs, and trace pharmaceuticals—can still pass through some RO membranes. This means you may get cleaner water, but not necessarily contaminant-free water.