Reverse osmosis at home: pros, cons and what it removes

Updated 2026-10-27 · Written from EPA, NSF, CDC and maker documents, each linked at the end · How we decide what to say

Short answer

Reverse osmosis is one of the few home technologies that reduces dissolved salts, many metals and PFAS in one step, but it wastes water, removes minerals, needs maintenance and only treats one tap. Look for NSF/ANSI 58 certification and, for waste, the WaterSense label.

How it works

An RO system uses pressure to push water through a membrane that limits the size of particles that can pass. The membrane rejects contaminants into a separate stream of “reject” water that goes to the drain, and the treated water goes to a faucet. Most residential units add carbon and sediment pre-filters and a polishing stage, so they are certified to more than one standard.

What it does well

EPA WaterSense lists these benefits: it improves taste and odor, removes sodium, dissolved inorganics and organics, and some systems can reduce nitrates, pesticides, dioxins, chloroform and petrochemicals. EPA also found RO point-of-use systems it studied can greatly reduce PFAS, and the Minnesota Department of Health lists RO among the technologies shown effective for PFAS when properly installed and maintained.

What to weigh against it

Wasted water. EPA estimates a typical POU RO system generates at least five gallons of reject water per gallon of treated water, and some inefficient models up to ten. WaterSense-labeled models generate 2.3 gallons or less. EPA’s PFAS filter page puts it at about one gallon for every gallon treated for the systems it described, so the range is wide; ask for the system’s recovery rating.
It does not remove everything. WaterSense notes RO “does not remove all inorganic and organic contaminants”, and that it also removes beneficial minerals such as calcium.
Cost and upkeep. WaterSense calls RO costly to install and maintain; it says RO systems typically cost more than pitchers and tap filters and may require professional installation, plus periodic filter and membrane replacement.
One tap. An under-sink unit treats the water you drink and cook with, not the whole house.
Extra treatment may be needed depending on incoming water quality (EPA’s PFAS filter page).

The certification

Look for NSF/ANSI 58 (Reverse Osmosis Drinking Water Treatment Systems). Because an RO system often includes carbon and other stages, specific claims such as lead or PFOA/PFOS may sit on a separate listing for a cartridge under NSF/ANSI 53 or 42. EPA’s advice: check the performance data sheet or the certifier’s database for the exact contaminant you care about (certifications explained).

Is RO the right choice for you?

It tends to make sense where your utility’s results or a lab test show contaminants that carbon alone does not address, such as dissolved salts or nitrate, or where you want a single system that covers a wide range. For lead alone, a certified carbon filter may be enough (lead filters).

Under-sink RO systems with certification listings

As an Amazon Associate this site earns from qualifying purchases, at no extra cost to you. Links are marked sponsored and never change what the data says. We list a product only where a certifier or the maker's data sheet supports the claim. We do not test products, and prices are on Amazon, not here. Certification is specific to a model and cartridge: confirm on the NSF database or IAPMO R&T listings before buying.

Waterdrop G3P600 under-sink reverse osmosis systemReverse osmosis at one tapListing: certified to NSF/ANSI 58 (TDS), 42 and 372; PFOA/PFOS claims appear on a separate NSF/ANSI 53 listing for its carbon cartridge. Needs power.Check the IAPMO or NSF listing for this exact model and cartridge. Many PFAS certificates on file test to under 20 ppt combined; NSF/ANSI 53-2025 aligns PFOA/PFOS with the 4 ppt federal limit, required of certified products by 2030. Check which the data sheet reflects.

iSpring RCC7AK-BN 6-stage alkaline reverse osmosis systemReverse osmosis at one tapListing: system certified to NSF/ANSI 58; under-sink with storage tank, no power needed. The listing also states PFAS reduction of 96-99%.NSF lists contaminant claims under the -BN and -BLK variants and TDS only for the plain RCC7AK; confirm the exact model. The PFAS figure is a manufacturer claim, not a certified one.

Not medical or legal advice. This guide summarizes public documents so you can ask better questions of your utility, your health department or a certified lab. For health concerns, talk to a clinician; for compliance questions, to your state drinking water program. Pages on this site that name products may earn a commission, as disclosed on the affiliate disclosure page.