The best reverse osmosis systems

Reverse osmosis systems can carry claims that kitchen carbon filters rarely do, for nitrate, arsenic and fluoride among them. But a system is certified only for the claims on its listing, and NSF/ANSI 58 requires just one: total dissolved solids. Every system here was checked against the certifiers' own listings: NSF, WQA and IAPMO. TapBuff has not tested these systems.

They are ranked by what those listings cover beyond the required claim, then by what each costs over five years at the maker's list prices, for a household of three using 3 gallons a day for drinking and cooking.

The picks at a glance

Filter	Pick	Certified for	Five years
Waterdrop G3P600	Best under-sink	Lead, PFOA, PFOS and 2 more	$1,149
AquaTru Classic (AT2000)	Most claims	Lead, Copper, PFOA and 8 more	$1,344
APEC Ultimate RO-90	Lowest five-year cost	Lead, Copper, Arsenic and 2 more	$549
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)	Most claims under the sink	Lead, Copper, PFOA and 8 more	$2,917
Five-year cost for a household of 3 at the makers’ list prices, cartridges included. A plus sign means a part due in those five years has no published price.

What NSF/ANSI 58 does and doesn't promise

Every system certified to NSF/ANSI 58 has to reduce total dissolved solids (TDS): the minerals and salts dissolved in water. That claim shows the membrane works. It doesn't say the system is certified for lead, arsenic, nitrate or fluoride. Each of those is a separate claim that a given system may or may not hold, and the listing names them one by one.

These systems carry the TDS claim and nothing more:

• iSpring RCC7 and RCC7AK. NSF lists both for TDS only. It lists the RCC7-BN, RCC7-BLK, RCC7AK-BN and RCC7AK-BLK, made at a different plant, with lead, fluoride and other claims. Check the model number on the box.
• APEC Essence ROES-50, ROES-100 and ROES-PH75. WQA lists all three for TDS only. APEC's RO-90, a pick below, is listed for lead, arsenic and fluoride as well.
• Express Water RO5DX and RO10DX. NSF lists both for TDS only.
• Waterdrop's X12, X14 and X16 tankless systems, and its K19 and M6 countertop units. IAPMO lists them for TDS only. Waterdrop's G3 systems carry more.
• A.O. Smith AOS-DFR800. IAPMO lists this tankless system for TDS only.

How the picks are ranked

What the listings cover comes first. A system with lead and PFAS claims ranks above one with a lead claim alone, which ranks above one listed for TDS only.

Then five-year cost. Each figure is the system's list price plus every filter and membrane due in five years, at the maker's list prices, with the first set in the box. Makers rate each stage in gallons, in months or both, and you replace it at whichever runs out first. The figure leaves out installation and the water sent down the drain. Where a maker publishes no price, there is no figure, rather than a guess.

The picks

Best under-sink

Under-sink reverse osmosis

Waterdrop G3P600

Best for lead, fluoride and PFOA/PFOS claims at the lowest five-year cost under the sink

Strengths

• Lead, fluoride, cadmium, barium and radium under NSF/ANSI 58, and PFOA/PFOS under NSF/ANSI 53, on IAPMO's listings
• The lowest five-year cost of the systems with lead and PFAS claims, at Waterdrop's list prices
• Tankless, and Waterdrop rates it at 2 gallons of filtered water for every 1 sent down the drain

Trade-offs

• No nitrate or arsenic claim
• The PFOA/PFOS claim is for its carbon block. Waterdrop's remineralization and alkaline add-ons are on no listing
• Three filters on three schedules, from six months to two years

Most claims

Countertop reverse osmosis

AquaTru Classic (AT2000)

Best for nitrate and arsenic as well as lead and PFAS, with no plumbing

Strengths

• Lead, nitrate and nitrite, arsenic, fluoride, copper, chromium and perchlorate under NSF/ANSI 58, and PFOA and PFOS under NSF/ANSI 53, on IAPMO's listings
• Sits on the counter and is filled by hand. No plumbing and no drain line
• AquaTru rates it at 75% efficiency

Trade-offs

• The water it rejects collects in the tap-water tank and has to be poured out
• Its arsenic claim covers pentavalent arsenic at 50 ppb or less
• Three filters, rated six months to two years; at 3 gallons a day they come due every 6 to 13 months

Lowest five-year cost

Under-sink reverse osmosis

APEC Ultimate RO-90

Best for a lead claim at the lowest five-year cost

Strengths

• Lead, arsenic, fluoride, copper, hexavalent chromium and radium under NSF/ANSI 58, on WQA's listing
• The lowest five-year cost of any reverse osmosis system TapBuff tracks
• Pre-filters once a year, and the membrane and post-filter every three years, by APEC's manual

Trade-offs

• No PFAS claim, and no NSF/ANSI 42 claim for chlorine taste and odor
• APEC publishes no gallon ratings and no waste ratio
• A storage tank to fit under the sink

Most claims under the sink

Under-sink reverse osmosis

Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)

Best for nitrate, arsenic and chloramine claims in a plumbed-in system

Strengths

• Lead, PFOA and PFOS, cysts and VOCs under NSF/ANSI 53, and nitrate, nitrite, arsenic, fluoride and chromium under NSF/ANSI 58, on WQA's listings
• Chlorine and chloramine under NSF/ANSI 42, and 16 claims under NSF/ANSI 401, microplastics among them
• A remineralizer stage comes with it

Trade-offs

• The highest five-year cost here: its carbon filters are rated for 250 gallons or six months, at $91.99 a set
• Aquasana's efficiency rating is 27.4%, about 2.6 gallons down the drain for each gallon filtered

Every reverse osmosis system TapBuff tracks

The picks come from this table. It lists every reverse osmosis system in TapBuff's catalog, under the sink and on the counter, and it changes as systems are added.

Reverse osmosis systems, by what their listings cover

Filter	Its listings cover	Refills	Five years
Lead and PFAS claims
Waterdrop G3P600Under-sink reverse osmosis, $539 to buy	Lead, PFOA, PFOS and 2 moreIAPMO 42, 53, 58	Every 6 months to 2 yearsCF composite filter: 550 gallons or 6 monthsCB carbon block filter: 1,100 gallons or 12 monthsRO filter: 2,200 gallons or 24 months	$1,149
AquaTru Classic (AT2000)Countertop reverse osmosis, $475 to buy	Lead, Copper, PFOA and 8 moreIAPMO 42, 53, 58, 401	Every 6 to 13 monthsPre/Carbon filter: 600 gallons or 6 monthsReverse osmosis filter: 1,200 gallons or 24 monthsVOC carbon filter: 600 gallons or 12 months	$1,344
Waterdrop G3P800Under-sink reverse osmosis, $999 to buy	Lead, PFOA, PFOS and 2 moreIAPMO 42, 53, 58	Every 6 months to 2 yearsCF composite filter: 550 gallons or 6 monthsCB carbon block filter: 1,100 gallons or 12 monthsRO filter: 2,200 gallons or 24 months	$1,669
Brondell Capella RC250 Reverse Osmosis SystemUnder-sink reverse osmosis, $330 to buy	Lead, Copper, PFOA and 7 moreWQA 42, 53, 58, 401	Every 3 months to 2 yearsSediment and carbon block set: 300 gallons or 6 monthsRO membrane: 24 months	$1,950
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)Under-sink reverse osmosis, $450 to buy	Lead, Copper, PFOA and 8 moreWQA 42, 53, 58, 401	Every 3 to 12 monthsCarbon block and advanced carbon block set: 250 gallons or 6 monthsRO membrane: 12 monthsRemineralizer: 6 months	$2,917
A lead claim
APEC Ultimate RO-90Under-sink reverse osmosis, $265 to buy	Lead, Copper, Arsenic and 2 moreWQA 58	Every 12 months to 3 yearsPre-filter set, stages 1 to 3: 12 monthsRO membrane: 36 monthsCarbon post-filter: 36 months	$549
Bluevua RO100ROPOT-Lite Countertop Reverse Osmosis SystemCountertop reverse osmosis, $349 to buy	Lead, Chromium (total)WQA 58	Every 12 months5-in-1 replacement filter: 12 monthsRemineralization filter 2-pack: 12 months	$805
Total dissolved solids only
APEC Essence ROES-50Under-sink reverse osmosis, $231 to buy	TDSWQA 58	Every 6 months to 2 yearsSediment filter: 3,000 gallons or 6 monthsCarbon block filters, two per change: 3,000 gallons or 6 monthsRO membrane: 24 monthsPost carbon filter: 24 months	$692
iSpring RCC7Under-sink reverse osmosis, $231 to buy	TDS ReductionNSF 58	Every 6 months to 2 yearsSediment filter: 6 monthsGAC carbon filter: 6 monthsCarbon block filter: 6 monthsPost carbon filter: 6 monthsRO membrane: 24 months	$1,100
Grouped by what their listings cover, then ranked by five-year cost: a household of 3 using 3 gallons a day for drinking and cooking, at the makers’ list prices, with the first filters in the box. “No price” means the maker publishes none. Listings checked between Oct. 4, 2026 and Oct. 9, 2026.

Water down the drain

A reverse osmosis membrane flushes what it rejects away with some of the water. By each maker's own figure, for every gallon of filtered water:

• Waterdrop G3P800: about a third of a gallon, rated 3 to 1.
• AquaTru Classic: about a third of a gallon, at a 75% efficiency rating. It collects in the tap-water tank rather than going down a drain.
• Waterdrop G3P600: half a gallon, rated 2 to 1.
• Brondell Capella: about 2.4 gallons, at a 29.1% efficiency rating on its data sheet. Brondell advertises 1 to 1.
• Aquasana SmartFlow: about 2.6 gallons, at a 27.4% efficiency rating.
• iSpring RCC7: 3 gallons, rated 1 to 3 with its tank.

APEC and Bluevua publish no figure. At 3 gallons of drinking water a day, the spread runs from about 1 gallon a day down the drain to 9. The five-year costs leave water out, since what it costs depends on your utility.

Arsenic: check the level and the type

The arsenic claims under NSF/ANSI 58 cover pentavalent arsenic, one of arsenic's two forms in water, at one of two levels: 50 ppb or 300 ppb. NSF's listings say a system with the claim is meant only for water shown to be at or below that level and of that form. The AquaTru and Aquasana claims are at 50 ppb; the APEC RO-90 and Brondell Capella claims are at 300 ppb. Test your water before you rely on any of them, and ask whether the lab can tell the two forms apart; arsenic and nitrate in well water explains why. The arsenic page has EPA's limit and what utilities report.

Under the sink or on the counter

• On the counter. The AquaTru Classic and Bluevua RO100ROPOT-Lite sit beside the sink and are filled by hand, so they suit renters and kitchens with no room under the sink.
• Under the sink, with a tank. The APEC, Aquasana, Brondell and iSpring systems fill a storage tank and send their reject water down the sink drain. They usually come with a faucet of their own.
• Under the sink, tankless. The Waterdrop G3 systems filter on demand and take less room.

Carbon filter or reverse osmosis?

For lead or PFOA and PFOS alone, a carbon filter certified under NSF/ANSI 53 can carry the claim for less, with no wastewater. The lead filter picks and PFAS filter picks include several, and the best under-sink water filters compares every one TapBuff tracks that fits under the sink. Reverse osmosis is where the nitrate, arsenic and fluoride claims are: in TapBuff's catalog, only reverse osmosis systems and one pitcher, the Culligan with ZeroWater technology, carry them.

Put in your own household's use in the five-year cost calculator, which starts with the four picks.

To see whether your utility reports nitrate, arsenic or fluoride: