A. O. Smith AOS-DFRO800
#8 in TanklessFull review
For a household that wants fast, certified tankless RO for less than most rivals. Buyers without a spare faucet should get the brushed nickel version.
Amazon $449.99 Amazon $484.99$449.99
3.2/5
For buyers who want a certified tankless system with remineralization and fast flow. Running costs are high, so it suits households that value the certification over cheap filters.
- 500 gallons a dayOutput
- 2:1Pure to drain
- $196 a yearFilters
- YesNSF/ANSI 58
Check price at Amazon$625.06
Price checked November 2, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- Fills an 8 oz glass in about 10 seconds, with no tank to wait on
- Sends one gallon to drain for every two it makes
- Certified to NSF/ANSI 58 as a complete system
- Adds minerals back for a less flat taste
Cons
- Filters cost close to $200 a year, among the highest in the category
- Needs an outlet under the sink
- Costs more than most 500 to 600 gpd tankless rivals
How it scores
The rating comes from 6 measured or published factors, each scored 0-100 against fixed reference points for its type. How we rank explains each one.
Specifications
| Model number | RO500AK-BN |
|---|---|
| Filtration | |
| Output | 500 gallons a day |
| Pure to drain | 2:1 |
| Stages | 3 |
| Remineralization | Yes |
| NSF/ANSI 58 | Yes |
| Replacement filters | $196 a year |
| Build | |
| Tank | Tankless |
| Booster pump | Yes |
| Smart faucet | No |
| Warranty | 1 year |
Alternatives in this type
Aquasana HealthShield RO
#9 in TanklessFull review
For a buyer who wants the broadest certification in a fast tankless system and doesn’t mind the price. Most households get similar output for much less elsewhere.
Amazon $1,299.99$1,299.99
Frizzlife PD600-TAM3
#11 in TanklessFull review
For a buyer who wants mineralized tankless RO with low running costs and accepts maker test claims instead of NSF 58 certification.
Amazon $399.49$399.49
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