The best under-sink water filters

An under-sink filter connects to the cold-water line in the cabinet below the kitchen sink and filters the water you drink at the tap. What it is certified to reduce is on its listing, and some are listed for chlorine, taste and odor only, or not listed at all. Every system here was checked against the certifiers' own listings, NSF, WQA and IAPMO, on October 16, 2026. TapBuff has not tested these systems.

They are ranked by what those listings cover, 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
Express Water StreamLine Direct Connect System (USC001)	Lowest five-year cost	Lead, PFOA, PFOS and 1 more	$527
Brondell Coral UC300 Under Sink Water Filtration System	Most claims for the money	Lead, PFOA, PFOS and 3 more	$900
Aquasana Claryum Direct Connect (AQ-MF-1)	Most claims on your own faucet	Lead, PFOA, PFOS and 3 more	$1,078
LARQ Under Sink Water Filter	Broadest PFAS claim	PFOA, PFOS, PFHxS and 3 more	$1,090
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.

Listed for chlorine, or not listed at all

NSF/ANSI 42 covers chlorine, taste and odor. It says nothing about lead or PFAS, which are claims under NSF/ANSI 53. Three under-sink filters stop at 42 or carry no listing at all:

• Waterdrop 10UA, 15UA and 17UA. IAPMO lists them under NSF/ANSI 42 for chlorine, taste and odor, and nothing else. Waterdrop says they reduce heavy metals and calls them third-party tested, which is not certification. The "NSF/ANSI 372" on its page is about the lead content of the filter's own parts, not lead in your water.
• iSpring US31. Its name on iSpring's store says "NSF Certified", and its description says it was tested by an independent third party against NSF/ANSI 42, 53 and 61. No listing for it was found at NSF, WQA or IAPMO. NSF lists iSpring only for reverse osmosis systems.
• Clearly Filtered's under-sink filter. WQA lists it under NSF/ANSI 42 for chlorine, taste and odor only.

If chlorine taste is all you want gone, the Waterdrop 10UA does that for $159 over five years. For lead or PFAS, the listing has to say so.

How the picks are ranked

What the listings cover comes first. A filter with lead and PFAS claims ranks above one with a lead claim alone, which ranks above one with health claims but no lead claim, then one listed for chlorine only, then one with no listing found.

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

The picks

Lowest five-year cost

Under-sink carbon

Express Water StreamLine Direct Connect System (USC001)

Best for lead and PFOA/PFOS claims for the least over five years

Strengths

• Lead and PFOA/PFOS under NSF/ANSI 53 on IAPMO's listing, with cysts, asbestos, atrazine, carbofuran and p-dichlorobenzene
• The lowest five-year cost of any under-sink filter here with a lead claim, at Express Water's list prices
• Connects to your existing faucet. One filter, rated 1,500 gallons or six months, at $48.99

Trade-offs

• No chloramine, mercury or VOC claim
• Feeds your own faucet, so dishwater and rinse water go through it too: above about 8 gallons a day it runs out before six months
• Seven claims under NSF/ANSI 401, where the Coral and the Claryum have 16. Microplastics are not among them
• PFOA and PFOS only: no Total PFAS claim

Most claims for the money

Under-sink carbon

Brondell Coral UC300 Under Sink Water Filtration System

Best for lead, PFOA/PFOS, chloramine and VOC claims for the least over five years

Strengths

• Lead, PFOA/PFOS, mercury, MTBE and VOCs under NSF/ANSI 53, on WQA's listing
• Chlorine, chloramine and Class I particulates under NSF/ANSI 42, and 16 claims under NSF/ANSI 401, microplastics among them
• Three filters replaced as a set, rated 600 gallons or 12 months: at 3 gallons a day, about every 7 months

Trade-offs

• $79.99 a set, and the stages are not sold separately
• Its own faucet goes through a separate 7/16-inch hole in the sink, so it takes some installing

Most claims on your own faucet

Under-sink carbon

Aquasana Claryum Direct Connect (AQ-MF-1)

Best for the Coral's health claims with no new faucet to install

Strengths

• Lead, PFOA/PFOS, mercury, MTBE and VOCs under NSF/ANSI 53, on IAPMO's listing
• Chlorine, chloramine and Class I particulates under NSF/ANSI 42, and 16 claims under NSF/ANSI 401, microplastics among them
• Connects to your existing faucet. One filter, rated 784 gallons or six months

Trade-offs

• $91.99 a filter at the one-time price, every six months
• Costs more over five years than the Coral, which carries the same health claims

Broadest PFAS claim

Under-sink carbon

LARQ Under Sink Water Filter

Best for PFAS beyond PFOA and PFOS

Strengths

• Total PFAS under NSF/ANSI 53 on NSF's listing: seven PFAS, PFOA, PFOS, PFHxS and PFNA among them
• The only under-sink filter here with a Total PFAS claim
• One filter every six months, rated 1,453 gallons

Trade-offs

• No lead claim on any listing. LARQ's lead figures come from independent testing, not certification, and LARQ says so
• $99 a filter at the one-time price

Every under-sink filter TapBuff tracks

The picks come from this table. It lists every under-sink filter in TapBuff's catalog, reverse osmosis aside, and it changes as filters are added.

Under-sink filters, by what their listings cover

Under-sink carbon	Its listings cover	Refills	Five years
Lead and PFAS claims
Express Water StreamLine Direct Connect System (USC001)$86 to buy	Lead, PFOA, PFOS and 1 moreIAPMO 42, 53, 401	Every 6 months1,500 gallons or 6 months each	$527
Brondell Coral UC300 Under Sink Water Filtration System$180 to buy	Lead, PFOA, PFOS and 3 moreWQA 42, 53, 401	Every 7 months600 gallons or 12 months each	$900
A.O. Smith 2-Stage Under Sink Water Filter (AO-US-200)$140 to buy	Lead, PFOA, PFOS and 3 moreWQA 42, 53, 401	Every 5 months500 gallons or 6 months each	$980
Aquasana Claryum 2-Stage (AQ-6200)$250 to buy	Lead, PFOA, PFOS and 3 moreWQA 42, 53, 401	Every 5 months500 gallons or 6 months each	$990
Aquasana Claryum Direct Connect (AQ-MF-1)$250 to buy	Lead, PFOA, PFOS and 3 moreIAPMO 42, 53, 401	Every 6 months784 gallons or 6 months each	$1,078
Aquasana Claryum 3-Stage Max Flow (AQ-6300M)$450 to buy	Lead, PFOA, PFOS and 3 moreWQA 42, 53, 401	Every 6 months800 gallons or 6 months each	$1,278
A lead claim
Frizzlife SK99 Under Sink Water Filter$126 to buy	Lead, ChlorineIAPMO 42, 53	Every 3 to 12 monthsSediment filter: 3 monthsCarbon block filter: 6 monthsCarbon block filter: 12 months	$590
Multipure Aquaversa (MP750)$550 to buy	Lead, Chlorine, Chloramine and 1 moreNSF 42, 53, 401	Every 8 months750 gallons or 12 months each	$1,215
Health claims, but not lead
LARQ Under Sink Water Filter$199 to buy	PFOA, PFOS, PFHxS and 3 moreNSF 42, 53	Every 6 months1,453 gallons or 6 months each	$1,090
Chlorine, taste and odor only
Waterdrop 10UA Under Sink Water Filter (WD-10UA)$59 to buy	ChlorineIAPMO 42	Every 12 months11,000 gallons or 12 months each	$159
No listing found
iSpring US31 3-Stage Under Sink Water Filtration System$143 to buy	Nothing found on NSF, WQA or IAPMO listings	Every 6 months6 months each	$431
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 Oct. 16, 2026.

Your own faucet, or a new one

• On your own faucet. The Express Water StreamLine, Aquasana Claryum Direct Connect, LARQ Under Sink, Frizzlife SK99 and Waterdrop 10UA connect to the cold-water line and feed the faucet you have, with no new hole. Every gallon of cold water from that faucet runs through the filter, rinse water included, so it can use more than the 3 gallons a day the five-year costs here assume. Above about 4 gallons a day, the Claryum Direct Connect runs out before its six months; the LARQ and the StreamLine, above about 8.
• With a faucet of its own. The Brondell Coral, A.O. Smith AO-US-200, Aquasana Claryum 2-Stage and 3-Stage Max Flow and iSpring US31 come with a separate drinking-water faucet, which needs a hole in the sink or the countertop. A.O. Smith's claims are for the version with its faucet.
• Either way. The Multipure Aquaversa sells as a base unit. Its below-sink kit with a faucet costs $70 to $90 more, and the five-year figure leaves that out.

A filter that screws onto the end of the faucet needs no installing at all, but its cartridge is rated for far less water. The best faucet water filters compares those.

If your utility uses chloramine

A chlorine claim doesn't cover chloramine, which some utilities use instead. Under NSF/ANSI 42, the Aquasana Claryum systems, A.O. Smith AO-US-200, Brondell Coral and Multipure Aquaversa carry chloramine claims. The Express Water StreamLine, Frizzlife SK99, LARQ and Waterdrop 10UA don't. Your utility's report on TapBuff shows which disinfectant it reported to EPA, and chlorine vs. chloramine explains the difference.

Carbon filter or reverse osmosis?

For lead and for PFOA and PFOS, a carbon filter under the sink can carry the claims for less than a reverse osmosis system, and it sends no water down the drain. Reverse osmosis is where the nitrate, arsenic and fluoride claims are: none of the carbon under-sink filters TapBuff tracks carries one. The best reverse osmosis systems compares those.

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

To see what your utility reports for lead, PFAS and its disinfectant: