Reverse osmosis explained: what an under-sink RO system does for Palos Heights homes

How it works

EPA describes RO as forcing water through a thin barrier, usually in a three-, four-, or five-stage process, that separates chemicals from the water. One stream is filtered drinking water; the other carries what was held back down the drain.

What it helps with (and what it doesn't)

• Lead: Yes — certified to reduce lead (NSF/ANSI 53/58)
• Chlorine by-products (TTHM): Yes — certified to reduce TTHM (NSF/ANSI 53/58)
• Chlorine taste & smell: Yes — at the kitchen sink
• Hard water & scale: No — not a softener
• PFAS ("forever chemicals"): Yes — certified to reduce PFOA/PFOS (NSF/ANSI 53/58)

Claims apply to the exact certified model and its listing. We write the model and certification on every quote.

What to know before you buy

• Certification: look for NSF/ANSI 58 for the RO system, plus the specific claims you care about (lead, PFOA/PFOS, VOCs).
• Maintenance: EPA notes RO needs its cartridges and membrane replaced on schedule to keep working.
• Water use: about one gallon goes down the drain for each gallon treated, per EPA.
• One tap: the filtered water comes from a dedicated faucet. Showers and laundry aren't affected.

Cost

EPA puts RO systems at roughly $150 to $1,000 before maintenance. Our under-sink RO starts at $1,195 installed by a licensed plumber — about 33¢ a day over 10 years before filter changes — with the exact model and certification listing written on your quote.

Prefer to start smaller? A certified pitcher is a real option too; see safe water on any budget.