Reverse osmosis

RO forces water through a membrane fine enough to reject most dissolved substances. It treats the water you drink and cook with — at one tap.

What it does

• Broad reduction of dissolved solids at a single point of use
• Specific models carry certified reduction claims for named contaminants — the claim is per contaminant, per model, and that's what a match means
• Often paired with carbon stages for taste

What it does not do

• An under-sink unit does not treat showers, laundry or the rest of the home
• It sends reject water to the drain — typically several gallons per gallon produced
• Whole-house RO exists but is rarely the right answer for a municipal home; treat that as a specialist conversation, not a default

When it fits

A confirmed lab result for a contaminant an RO model is certified to reduce, or a drinking-water taste concern at one tap. If your evidence is a symptom or a news story, a qualifying test comes first — certified claims only match named, measured contaminants.