A. O. Smith AO-US-200 2-Stage Under Sink Filter review
By Daryna Klochko · Published · Specs checked Oct 15, 2026 · 
Scores 9.75/10, tied for 7th of the 32 under-sink filters we track. At $111.11 it costs less than the category median of $199.50. Its cartridge cost of about $168 a year is level with the $168-a-year median of the 32 under-sink filters with a stated cartridge cost. Buyers on Amazon rate it 4.4/5 across 305 ratings.
The widest listing: 7 substances in the WQA listing, tied for the most among the 32 under-sink filters
- Price
- $111.11
- Certified for
- Lead · Cysts · VOCs +6
- Flow
- 0.5 gpm
- Cartridge life
- 500 gal
- Cost per year
- $168
- Warranty
- 1 year limited
Certification
Listed by WQA under NSF/ANSI 42 · 53 · 401 for Chlorine, Chloramine, Lead, Cysts, VOCs, PFOA/PFOS, Microplastics, checked Oct 15, 2026. Search the WQA listings
- Chlorine
- Chloramine
- Lead
- Cysts
- VOCs
- PFOA/PFOS
- Microplastics
The contaminants or other substances removed or reduced by this water treatment device are not necessarily in your water. Listing checked on Oct 15, 2026. What a listing means and what it doesn't
Specs and sources
Checked Oct 15, 2026 · source under each valueFiltration
Cartridges and install
Buying
Warranty, returns and shipping
Warranty: 1 year limited. Returns: Set by the retailer. Shipping: not stated by the brand. Source: A. O. Smith data sheet, checked Oct 15, 2026.
Source: A. O. Smith data sheet, checked Oct 15, 2026.
Compared with similar under-sink filters
All 32 under-sink filters →| Model | Price | Certified for | Cost per year | Warranty | Score | Where to buy |
|---|---|---|---|---|---|---|
| A. O. Smith AO-US-200 2-Stage Under Sink FilterTHIS MODEL | $111.11 | Lead · Cysts +7 | $168 | 1 year limited | 9.75/10 | Check price → |
| Doulton QT Under Counter System (Ultracarb) | $119.99 | Lead · Cysts +2 | $42 | 3 years (limited) | 9.5/10 | Check price → |
| A. O. Smith AO-MF-ADV Advanced Direct Connect Faucet Filter | $119.99 | Lead · Cysts +5 | $187 | 1 year limited | 9.75/10 | Check price → |
| Frizzlife SK99 3-Stage Under Sink Water Filter | $125.99 | Lead · Cysts +1 | $95 | 1 year | 10/10 | Check price → |
| Epic Water Filters Smart Shield Under Sink | $129 | Lead · Cysts +3 | $115 | 3 years limited | 9.75/10 | Check price → |
What owners say
Checked Oct 15, 20264.4/5 from 305 ratings on Amazon. In our score this is 2 of 2 points. How we score
- Installation32 mentions27 positive5 negative
- Water flow30 mentions19 positive11 negative
- Water taste21 mentions20 positive1 negative
- Value for money16 mentions6 positive10 negative
- Leakage14 mentions5 positive9 negative
- Durability10 mentions1 positive9 negative
- Filtration performance9 mentions8 positive1 negative
Store ratings change over time; the date shows when we checked.