Express Water RO5DX
#6 in With tankFull review
For a budget buyer who wants a certified system with cheap filters. Anyone paying for water or on a septic system should pick a lower waste design.
Amazon $179.99$179.99
The Express Water RO5DX is the better under-sink reverse osmosis system overall, rated 3.6 to 2.8. The Express Water RO5DX leads on filter cost and price. The Aquasana SmartFlow RO wins on warranty. The Express Water RO5DX costs $300 less ($179.99 vs $479.99).
Aquasana SmartFlow RO
#13 in With tankFull review
For a buyer who wants the broadest certification and mineralized water in a tank system. The running cost is high, so budget buyers should look elsewhere.
Aquasana $479.99$479.99
Prices were last checked November 2, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Express Water RO5DX for filter cost ($81 a year in replacement filters vs $310 a year in replacement filters) and price ($179.99 vs $479.99).
- Choose the Aquasana SmartFlow RO for warranty (2-year warranty vs 1-year warranty).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every with tank under-sink reverse osmosis system; a clear win is highlighted. How we rank explains each one.
| Factor weight | Express Water RO5DX | Aquasana SmartFlow RO |
|---|---|---|
| Overall rating | 3.6/5 | 2.8/5 |
| Certification 25% | 100 certified to NSF/ANSI 58 | 100 certified to NSF/ANSI 58 |
| Filter cost 20% | 70 $81 a year in replacement filters | 0 $310 a year in replacement filters |
| Water wasted 15% | 50 drain ratio not published (neutral score used) | 50 drain ratio not published (neutral score used) |
| Output 10% | 0 50 gallons a day | 3 51.4 gallons a day |
| Price 15% | 85 $179.99 | 3 $479.99 |
| Warranty 15% | 0 1-year warranty | 25 2-year warranty |
Independent measurements
Express Water RO5DX
| Tested by | TDS reduction | Output | Pure to drain | Conditions |
|---|---|---|---|---|
| Water Filter Guru | - | 51.8 gpd | - | At 48 psi and 58.6 F. |
| Water Filter Guru | - | - | 0.2 :1 | 64 oz purified to 336 oz drained (1:5.25); a 12 oz test gave 1:5.9. |
Aquasana SmartFlow RO
| Tested by | TDS reduction | Output | Pure to drain | Conditions |
|---|---|---|---|---|
| Water Filter Guru | 95.4 % | - | - | TDS before and after filtration on the reviewer’s tap water. |
| Water Filter Guru | - | 44.6 gpd | - | At 51 psi and 59.2 F. |
| Water Filter Guru | - | - | 0.5 :1 | 64 oz test gave 1:2; a 12 oz test gave 1:2.25. |
Specifications
| Express Water RO5DX | Aquasana SmartFlow RO | |
|---|---|---|
| Filtration | ||
| Output | 50 gallons a day | 51.4 gallons a day |
| Stages | 5 | 4 |
| Remineralization | No | Yes |
| NSF/ANSI 58 | Yes | Yes |
| Other certifications | NSF/ANSI 372 | NSF/ANSI 42, 53, 372, 401 |
| Replacement filters | $81 a year | $310 a year |
| Build | ||
| Tank | 3.2 gal | 3.2 gal |
| Booster pump | No | No |
| Smart faucet | No | No |
| Warranty | 1 year | 2 years |
| Released | - | 2023 |