Reverse osmosis (RO)

Reverse osmosis

Stasis Home Research Every claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated June 2026

Reverse osmosis, usually shortened to RO, is an under-sink filter that pushes water through a membrane fine enough to strain out dissolved contaminants that a carbon filter misses.

What does Reverse osmosis (RO) mean?

Installed under the kitchen sink, reverse osmosis forces water under pressure through a semi-permeable membrane, and it covers the widest range of dissolved contaminants of any point-of-use filter. It removes the large majority of both long- and short-chain PFAS, along with lead, hexavalent chromium, nitrate, and perchlorate, the soluble compounds an ordinary carbon filter leaves in the water. Two tradeoffs come with that reach. RO sends a portion of each batch down the drain as reject water, so it uses more water per glass produced than a carbon filter. It also strips out the beneficial minerals, like calcium and magnesium, that carbon filtration leaves intact. RO works at the tap, treating the drinking-water route only. It does nothing about PFAS or other exposures that arrive through food, packaging, or household dust.