AO Smith water filter review: what each model is certified for
5 filters: 3 under-sink filters, 1 RO system and 1 whole-house system, $79.99 to $474.99. An AO Smith water filter from Lowe’s or Amazon is certified for lead if it’s one of the three under-sink models, and for chlorine only if it’s the whole house tank. As of October 15, 2026, WQA lists the AO-US-200 and IAPMO lists the AO-MF-ADV to NSF/ANSI 53 for lead, mercury, PFOA/PFOS and VOCs. IAPMO lists the smaller AO-MF for lead but not PFAS, and NSF lists the AO-WH-FILTER to NSF/ANSI 42 for chlorine. Fluoride appears only in A. O. Smith’s reverse osmosis listings. A. O. Smith also owns Aquasana, and the two lines share the Claryum filter name.
By Daryna Klochko · Published · Prices and listings checked Oct 15, 2026 All 5 A. O. Smith filters
Listing: "certified" counts only substances in the certifier's public listing for that model. A. O. Smith's own reduction claims that are not in a listing are shown separately on each model page.
Verdict: which A. O. Smith filter to buy and what to skip
The AO-MF is listed for lead, cysts, atrazine and lindane, and its cartridge is rated for 1,389 gallons. At Amazon prices on October 15, 2026, its cartridges cost about $110 a year, the least of A. O. Smith’s under-sink filters.
NSF lists the AO-WH-FILTER for chlorine taste and odor only. Leaks are its most negative topic on Amazon: 57 of 72 mentions.
Two A. O. Smith RO systems at Lowe’s are listed for fluoride, and neither is sold on Amazon. The store-linked RO from the same company is Aquasana’s SmartFlow RO.
Alternatives worth considering: Aquasana, the same company
A. O. Smith Water Treatment (North America), Inc. owns Aquasana. The company is named on Aquasana’s warranty. A. O. Smith’s Lowe’s pages call its under-sink cartridges Claryum, the name Aquasana uses for its own filters. So the closest alternatives to A. O. Smith are Aquasana models, sold from Aquasana’s own store. The full lineup is in our Aquasana review.
Prices, cartridge costs and listings checked October 15, 2026
The AO-MF-ADV and the Claryum Direct Connect have the same published specs: a cartridge rated for 784 gallons or 6 months, 1.5 gpm, a 1-year limited warranty. They hold separate IAPMO certificates, and only the Aquasana is listed for chlorine and chloramine. On October 15, 2026 the A. O. Smith cost $119.99 on Amazon and the Aquasana $249.99 at Aquasana. The AO-US-200 and the Claryum 3-Stage both cost $168 a year to run. The Aquasana adds a third stage and a 600-gallon cartridge, against 500 for the A. O. Smith.
The contaminants or other substances removed or reduced by this water treatment device are not necessarily in your water. All under-sink models are compared in the best under-sink water filters. You can also browse all water filters by type.
The AO Smith water filter lineup: Lowe’s, Amazon and dealers
A. O. Smith sells water filters through two channels. The retail line on A. O. Smith at Lowe’s is marked “Lowes Exclusive” for stores, and the same models are sold on Amazon by A. O. Smith Water Treatment. The dealer line on aosmith.com, with HomeShield, InterFlo and the AORO-50 RO system, goes through installers. Its older AOW-100, AOW-2000 and AOW-3000 are marked “series discontinued”. This review covers the retail line.
| Model | Type | Price | Standards in the listing | Sold at |
|---|---|---|---|---|
| AO-US-200 | Under sink, own faucet | $111.11 (MSRP $139.99) | 42, 53, 401 (WQA) | Lowe’s, Amazon |
| AO-MF-ADV | Under sink, your faucet | $119.99 | 53, 401 and 42 (IAPMO) | Lowe’s, Amazon |
| AO-MF | Under sink, your faucet | $79.99 | 42, 53, 401 (IAPMO) | Lowe’s, Amazon |
| AO-MF-B | Under sink, chlorine only | Not shown | 42 (NSF) | Lowe’s |
| AO-US-RO-MB-4000 | Reverse osmosis with remineralizer | Not shown | 42, 53, 58, 401 (IAPMO) | Lowe’s |
| AOS-HERO-CHR | Reverse osmosis | MSRP $249.99 | 42, 53, 58, 401 (WQA) | Lowe’s |
| AOS-DFRO800 | Tankless reverse osmosis | $474.99 | 58, TDS only (IAPMO) | Amazon |
| AO-WH-FILTER | Whole house carbon tank | $399.99 (MSRP $349.99) | 42 (NSF) | Lowe’s, Amazon |
| AO-WH-PREL | Whole house sediment pre-filter | $76.99 | 42, as a component (NSF) | Lowe’s, Amazon |
| AO-FF | Refrigerator line filter | MSRP $39.99 | 42, 53, 401 (WQA) | Lowe’s |
The UV system, AO-WH-UV, and the salt-free descaler, AO-WH-DSCLR, are also on the Lowe’s site. I found no listing for either under A. O. Smith. The softeners are listed by NSF to NSF/ANSI 44.
Is AO Smith NSF certified? The listings by certifier
Yes, but by three certifiers and not always for everything the box says. WQA, IAPMO and NSF all certify to NSF/ANSI standards. I matched each retail model against all three databases on October 15, 2026.
| Model | Certifier | What the listing names | What the brand adds |
|---|---|---|---|
| AO-US-200 | WQA | 53: lead, mercury, PFOA, PFOS, VOCs, cysts, asbestos, MTBE. 42: chlorine, chloramine. 401: 15 chemicals and microplastics | “Reduces up to 99% of 78 harmful contaminants” (Lowe’s page) |
| AO-MF-ADV | IAPMO | 53: lead, mercury, PFOA/PFOS, VOCs, cysts, asbestos, MTBE. 401: 6 chemicals and microplastics. 42: the row repeats the 401 list and names no chlorine | Chlorine (Lowe’s page) |
| AO-MF | IAPMO | 42: chlorine. 53: lead, cysts, atrazine, lindane. 401: microplastics | — |
| AO-US-RO-MB-4000 | IAPMO | 58: fluoride, arsenic (V), lead, chromium 6, radium, copper, TDS and more. 53: PFOA/PFOS, VOCs. 42: chlorine, chloramine | “Certified to standard 42, 53, 58, 401, P473 and P231” (Lowe’s page); no P473 or P231 row in the listing |
| AOS-HERO-CHR | WQA | 58: fluoride, arsenic (V), nitrate, nitrite, chromium 6, radium and more. 53: lead, PFOA, PFOS, VOCs. 42: chlorine, chloramine | — |
| AO-WH-FILTER | NSF | 42: chlorine, taste and odor | “Reduces Chloramine: Yes” in the specs (Lowe’s page) |
| AOS-DFRO800 | IAPMO | 58: TDS only | Chlorine, 99.4% in A. O. Smith’s own test (data sheet) |
P231 is the protocol for microbiological water purifiers. The RO-MB-4000 page makes a microbial claim for its remineralizer stage, and the IAPMO listing has no row for that protocol. The AO-US-200 Amazon listing gives its standards as “42, 43 and 401”; there is no NSF/ANSI 43 row in the WQA listing.
A listing tells you what a filter is certified to reduce, not what’s in your tap water. A lead test tells you whether you need it. Other brands’ lead listings are in lead-certified water filters. The contaminants or other substances removed or reduced by this water treatment device are not necessarily in your water.
A. O. Smith reverse osmosis: fluoride is in two listings
A. O. Smith has three retail RO systems, and the two listed for fluoride are sold at Lowe’s, not on Amazon. The AO-US-RO-MB-4000 is listed by IAPMO under NSF/ANSI 58 for fluoride, arsenic (V), lead, chromium 6 and radium, and under 53 for PFOA/PFOS. Its Lowe’s page, checked October 15, 2026, puts the stage 1 and 3 filters at 6 months or 365 gallons and the yearly cost at $240. The same page gives the membrane 12 months in the feature list and 2 years in the replacement section.
The AOS-HERO-CHR is listed by WQA for fluoride, nitrate and nitrite under NSF/ANSI 58. Its MSRP on October 15, 2026 was $249.99, and its flow is 0.8 gpm by A. O. Smith’s figure. Its membrane is sold as the “SmartFlow RO Membrane”, the name of Aquasana’s RO system.
The tankless AOS-DFRO800 was $474.99 on Amazon on October 15, 2026. It has leak detection with an automatic shutoff and makes 800 gallons a day in the IAPMO listing. IAPMO lists it under NSF/ANSI 58 for TDS only, and TDS is a measure of dissolved minerals, not of safety. Its data sheet gives a 64% efficiency rating, about half a gallon to the drain per gallon kept. The AOS-DFRO-CPP carbon filter is $79.99 for 6 months or 365 gallons, and the AOS-DFRO-ROM membrane $129.99 at A. O. Smith’s list price for 12 months or 730 gallons: about $290 a year.
For fluoride with a store link here, the Aquasana SmartFlow RO is listed by WQA for fluoride, arsenic, lead and PFOA/PFOS. It was $449.99 on October 15, 2026, about $310 a year in filters. More options are in the best reverse osmosis systems and filters certified for fluoride. The contaminants or other substances removed or reduced by this water treatment device are not necessarily in your water.
AO Smith whole house water filter: chlorine only, and leaks
The AO-WH-FILTER is a single carbon tank on the main line, rated for 6 years or 600,000 gallons at 7 gpm. NSF lists it to NSF/ANSI 42 for chlorine reduction and taste and odor, nothing else. The Lowe’s page lists “Reduces Chloramine: Yes” in its specs. Chloramine isn’t in the listing. The Amazon listing says it isn’t a water softener, won’t reduce TDS, sulfur or iron, and recommends a pre-filter. A. O. Smith’s sediment pre-filter, the AO-WH-PREL, was $76.99 on Amazon on October 15, 2026.
Owners like the water: 25 of 28 water-taste mentions are positive. Leaks are the problem: 57 of 72 leakage mentions are negative, 2.9% of all 1,980 ratings, and durability is negative in 29 of 45. Value for money splits 57 to 37.
The tank has a 6-year limited warranty. The NSF listing names a replacement element, AO-WH-FILTER-R, but neither Lowe’s nor Amazon sold it on October 15, 2026, so I couldn’t price the seventh year. If lead or PFAS is the worry, a whole house carbon tank isn’t the fix. An under-sink filter with an NSF/ANSI 53 listing is. Tanks with wider listings are in the best whole house water filters.
AO Smith replacement filters: what a year costs
A. O. Smith’s yearly figures are lower than what the cartridges cost on Amazon. The under-sink cartridges and the RO carbon stages last 6 months, so a year is two of each.
| System | Replacement | Amazon price | Per year on Amazon | A. O. Smith’s yearly figure |
|---|---|---|---|---|
| AO-US-200 | AO-US-200-R, stage 1 and 2 set | $83.99 | $168 | “$120 or Less” |
| AO-MF-ADV | AO-MF-ADV-R | $93.49 | $187 | $140 |
| AO-MF | AO-MF-R | $54.99 | $110 | Not shown |
| AOS-HERO-CHR | AOS-HERO-S1S3 every 6 months, AOS-HERO-S2 membrane every 12 | $99.99 and $69.99 | $270 | $220 |
| AOS-DFRO800 | AOS-DFRO-CPP every 6 months, AOS-DFRO-ROM membrane every 12 | $79.99; membrane $129.99 MSRP | $290 | Not shown |
The AO-US-200 cartridge set has 1,561 Amazon ratings at 4.6 stars, but value for money is the weak topic: 40 of 69 mentions are negative. A. O. Smith rates the under-sink cartridges by gallons too: 500 for the AO-US-200, 784 for the AO-MF-ADV, 1,389 for the AO-MF. A big household can reach the gallon limit before 6 months.
Does AO Smith filter fluoride, PFAS or bacteria?
- Fluoride: only the two RO systems at Lowe’s, the AO-US-RO-MB-4000 and the AOS-HERO-CHR, are listed for it. No under-sink carbon filter and not the whole house tank.
- PFAS: PFOA and PFOS are in the NSF/ANSI 53 listings of the AO-US-200, the AO-MF-ADV, the AO-FF refrigerator filter and both Lowe’s RO systems. The AO-MF and the whole house filter aren’t listed for PFAS. The dealer-line HomeShield AOS-HS-1200 is listed by WQA for five PFAS, including PFHxS and PFNA, and is sold through installers.
- Bacteria and viruses: no A. O. Smith listing I found covers them. The UV system has no NSF/ANSI 55 listing under A. O. Smith, and the RO-MB-4000 listing has no P231 row.
- TDS: only the RO systems reduce it. The AO-US-200 Amazon listing says it won’t.
The contaminants or other substances removed or reduced by this water treatment device are not necessarily in your water.
What AO Smith owners say
I checked the Amazon ratings and Amazon’s review topics for the four models on October 15, 2026. Each is sold by A. O. Smith Water Treatment.
- AO-US-200: 4.4 stars from 305 ratings. Installation is praised in 27 of 32 mentions and taste in 20 of 21. Durability is negative in 9 of 10, leakage in 9 of 14, value in 10 of 16, and water flow in 11 of 30.
- AO-MF-ADV: 4.4 stars from 180 ratings. Installation is praised in 21 of 27; leakage is negative in 8 of 13 and water flow in 6 of 11.
- AO-MF: 4.5 stars from 72 ratings, with no negative mentions of installation, quality or taste so far.
- AO-WH-FILTER: 4.3 stars from 1,980 ratings. Leakage is negative in 57 of 72.
Leaks show up in every model with enough reviews to have a leakage topic. Check the fittings for the first days after you install one.
Warranty, returns and where to buy
The warranties are limited: 1 year on the under-sink filters, 2 years on the RO systems and 6 years on the whole house filter. In stores, the retail line is a Lowe’s exclusive. Online, A. O. Smith Water Treatment sells it on Amazon, where the AO-MF-ADV and AO-MF pages showed a 30-day return window on October 15, 2026; the AO-US-200 and whole house filter pages didn’t state one. The dealer line on aosmith.com is sold and installed by local dealers.
Questions people ask
Is AO Smith the same company as Aquasana?
Does an AO Smith water filter reduce lead?
Does AO Smith filter fluoride?
How often do you change an AO Smith water filter?
Where can I buy AO Smith water filters?
Does the AO Smith whole house filter soften water?
Does AO Smith reduce TDS?
Listing by model
NSF, WQA and IAPMO public listings, checked Oct 15, 2026. The contaminants or other substances removed or reduced by these devices are not necessarily in your water.