Reverse osmosis (RO) pushes water through a membrane fine enough to remove most dissolved solids, along with many contaminants a basic carbon filter misses. The certification that matters is NSF/ANSI 58, the standard for RO systems. We list every standard each system is certified to, and say when a figure is only the maker's claim.
- Best overallWaterdrop G3P800$999 list
- Best value tanklessWaterdrop G3P600About $439
- Best no-installAquaTru Classic$475 list
- Best budgetiSpring RCC7AK$229.99 list
- Best basic tank systemAPEC ROES-50$230.99 list
Side by side
| Model | Price | Type | Gallons per day | Pure to drain | Certified to | Power |
|---|---|---|---|---|---|---|
| Waterdrop G3P800 | $999 list | Tankless | 800 | 3:1 | NSF/ANSI 42, 53, 58, 372 | Needs an outlet |
| Waterdrop G3P600 | About $439 | Tankless | 600 | 2:1 | NSF/ANSI 42, 53, 58, 372 | Needs an outlet |
| AquaTru Classic | $475 list | 0.75 gal clean tank | Batch | 4:1 (claimed) | NSF/ANSI 42, 53, 58, 401 | Needs an outlet |
| iSpring RCC7AK | $229.99 list | 3.2 gal tank | 75 | About 1:3 (reported) | NSF/ANSI 58 | No electricity |
| APEC ROES-50 | $230.99 list | 4 gal tank | 50 | About 1:3 (reported) | NSF/ANSI 58, 372 | No electricity |
Waterdrop G3P800
- Price
- $999 list
- Type
- Tankless
- Gallons per day
- 800
- Pure to drain
- 3:1
- Certified to
- NSF/ANSI 42, 53, 58, 372
- Power
- Needs an outlet
The G3P800 is a tankless under-sink system rated at 800 gallons per day with a 3:1 pure-to-drain ratio, the best waste ratio of any under-sink system here. It's certified by IAPMO R&T to NSF/ANSI 42, 53, 58 and 372, adds a UV light, and comes with a faucet that shows water quality (TDS) and filter life.
Filters cost about $160 a year: a $29.99 carbon filter every six months, a $29.99 carbon block every year and a $139.99 RO membrane every two years. It needs an outlet under the sink, and the warranty is just one year.
What we like
- 800 GPD, 3:1 ratio
- Certified to NSF/ANSI 42, 53, 58 and 372
- UV light and smart faucet
What to know
- $999 list (often on sale)
- Needs an outlet
- 1-year warranty
Waterdrop G3P600
- Price
- About $439
- Type
- Tankless
- Gallons per day
- 600
- Pure to drain
- 2:1
- Certified to
- NSF/ANSI 42, 53, 58, 372
- Power
- Needs an outlet
The G3P600 is the G3P800 minus the UV light and smart faucet, for about $439. It's rated at 600 GPD with a 2:1 ratio and carries the same NSF/ANSI 42, 53, 58 and 372 listings. Filters run about $145 a year.
What we like
- About $439
- Same certifications as the G3P800
What to know
- No UV or smart faucet
- Wastes more water than the G3P800
AquaTru Classic
- Price
- $475 list
- Type
- 0.75 gal clean tank
- Gallons per day
- Batch
- Pure to drain
- 4:1 (claimed)
- Certified to
- NSF/ANSI 42, 53, 58, 401
- Power
- Needs an outlet
The AquaTru Classic sits on the counter. You fill its tank from the tap, it filters into a 0.75-gallon clean-water tank, and you pour. It's certified to NSF/ANSI 42, 53, 58 and 401 and AquaTru claims a 4:1 ratio. The RO membrane lasts up to two years or 600 gallons.
It's ideal for renters, but it uses counter space and makes water in batches, so it suits one or two people best.
What we like
- No plumbing
- Certified to NSF/ANSI 42, 53, 58 and 401
What to know
- Small clean tank
- Uses counter space
iSpring RCC7AK
- Price
- $229.99 list
- Type
- 3.2 gal tank
- Gallons per day
- 75
- Pure to drain
- About 1:3 (reported)
- Certified to
- NSF/ANSI 58
- Power
- No electricity
A classic under-sink tank system for $229.99, with six stages including an alkaline remineralization filter, NSF/ANSI 58 certification and a 3.2-gallon tank. It needs no electricity, and a year of filters costs about $81.
Tank systems waste more water, roughly 1:3 by reported figures, and fill a glass more slowly than tankless ones.
What we like
- $229.99 list
- About $81 a year in filters
- No electricity
What to know
- Wastes more water
- Large tank under the sink
APEC ROES-50
- Price
- $230.99 list
- Type
- 4 gal tank
- Gallons per day
- 50
- Pure to drain
- About 1:3 (reported)
- Certified to
- NSF/ANSI 58, 372
- Power
- No electricity
APEC's ROES-50 is a long-running budget favorite: five stages, a 4-gallon tank, NSF/ANSI 58 and 372 listings and a 2-year warranty, at $230.99 list and often less. It's rated at 50 GPD and has no remineralization stage.
What we like
- 2-year warranty
- 4-gallon tank
- No electricity
What to know
- 50 GPD
- No remineralization
Tankless or tank?
Tankless systems are faster, smaller and waste less water, but need an outlet and cost more. Tank systems are cheaper and need no power. See tankless vs tank RO.
Questions
Does RO remove minerals?
Yes, most of them. Some systems add a remineralization stage to put a little calcium and magnesium back for taste.
How much water does RO waste?
It depends on the system. The ratio tells you: 3:1 means three gallons of clean water for every gallon sent to the drain.
Can I use RO water in my ice maker?
Yes. Countertop ice makers are filled by hand, so you fill from the RO faucet. Check your ice maker's manual for any water guidance.
