Waterdrop G3P600
#4 in TanklessFull review
For a household that wants a certified tankless RO system with a smart faucet at a mid-range price. Its NSF 58 listing is the main reason to pick it over cheaper tankless units.
Amazon $439$439
The Waterdrop G3P600 is the better under-sink reverse osmosis system overall, rated 3.6 to 2.9. The Waterdrop G3P600 leads on certification. The iSpring RO600 wins on filter cost. The iSpring RO600 costs $9.01 less ($429.99 vs $439).
iSpring RO600
#15 in TanklessFull review
For buyers who want fast tankless RO with little wasted water and cheap filters. Pick a certified model if third-party proof of performance matters.
Amazon $429.99$429.99
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 Waterdrop G3P600 for certification (certified to NSF/ANSI 58 vs no third-party certification).
- Choose the iSpring RO600 for filter cost ($98 a year in replacement filters vs $145 a year in replacement filters).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every tankless under-sink reverse osmosis system; a clear win is highlighted. How we rank explains each one.
| Factor weight | Waterdrop G3P600 | iSpring RO600 |
|---|---|---|
| Overall rating | 3.6/5 | 2.9/5 |
| Certification 25% | 100 certified to NSF/ANSI 58 | 0 no third-party certification |
| Filter cost 20% | 34 $145 a year in replacement filters | 58 $98 a year in replacement filters |
| Water wasted 15% | 95 2:1 pure to drain | 98 2.5:1 pure to drain |
| Output 10% | 43 600 gallons a day | 43 600 gallons a day |
| Price 15% | 56 $439 | 58 $429.99 |
| Warranty 15% | 0 1-year warranty | 0 1-year warranty |
Specifications
| Waterdrop G3P600 | iSpring RO600 | |
|---|---|---|
| Filtration | ||
| Output | 600 gallons a day | 600 gallons a day |
| Pure to drain | 2:1 | 2.5:1 |
| Stages | 8 | 2 |
| Remineralization | No | No |
| NSF/ANSI 58 | Yes | No |
| Other certifications | NSF/ANSI 42, 53, 372 | - |
| Replacement filters | $145 a year | $98 a year |
| Build | ||
| Tank | Tankless | Tankless |
| Booster pump | Yes | Yes |
| Smart faucet | Yes | No |
| Warranty | 1 year | 1 year |