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The Best Tankless Reverse Osmosis Systems of 2021

Here we provide a detailed comparison of the best tankless reverse osmosis systems to complement our standard reverse osmosis system reviews.

The best tankless reverse osmosis systems

Tankless reverse osmosis water filtrations systems have unique features and benefits that make them a very compelling option for filtering your drinking water.

If you are looking for a great reverse osmosis water filter, then a tankless RO system may be the best current option.

Waterdrop G3 RO System
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Frizzlife PD600-TAM3 RO with Remineralization
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NU Aqua Tankless 600 GPD
Waterdrop G2 P600 RO System
Our Rating
Stages
7
7
4
6
Output
400 GPD
600 GPD
600 GPD
600 GPD
Wasted Water
1 Gal : 1 Gal Filtered
1 Gal : 1.5 Gal Filtered
1 Gal : 2 Gal Filtered
1 Gal : 2 Gal Filtered
Smart Faucet
Real-time TDS Reading
Filter Life Indicator
Water Leak Detector
Remineralization
Optional Add-on
Optional Add-on
Size
18.06" x 5.68" x 17.76"
14.7" x 5.3" x 15.5"
9.25" x 9.75" x 18.25"
17.32" x 5.91" x 13.9"
Relative Price
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Waterdrop G3 RO System
Model
Our Rating
Stages
7
Output
400 GPD
Wasted Water
1 Gal : 1 Gal Filtered
Smart Faucet
Real-time TDS Reading
Filter Life Indicator
Water Leak Detector
Remineralization
Optional Add-on
Size
18.06" x 5.68" x 17.76"
Relative Price
Our Review
Free Shipping
Learn More/Buy
ON SALE NOW!
Frizzlife PD600-TAM3 RO with Remineralization
Our Rating
Stages
7
Output
600 GPD
Wasted Water
1 Gal : 1.5 Gal Filtered
Smart Faucet
Real-time TDS Reading
Filter Life Indicator
Water Leak Detector
Remineralization
Size
14.7" x 5.3" x 15.5"
Relative Price
Our Review
Free Shipping
Learn More/Buy
ON SALE NOW!
NU Aqua Tankless 600 GPD
Our Rating
Stages
4
Output
600 GPD
Wasted Water
1 Gal : 2 Gal Filtered
Smart Faucet
Real-time TDS Reading
Filter Life Indicator
Water Leak Detector
Remineralization
Size
9.25" x 9.75" x 18.25"
Relative Price
Our Review
Free Shipping
Learn More/Buy
Waterdrop G2 P600 RO System
Our Rating
Stages
6
Output
600 GPD
Wasted Water
1 Gal : 2 Gal Filtered
Smart Faucet
Real-time TDS Reading
Filter Life Indicator
Water Leak Detector
Remineralization
Optional Add-on
Size
17.32" x 5.91" x 13.9"
Relative Price
Our Review
Free Shipping
Learn More/Buy

What is Reverse Osmosis?

Reverse osmosis water filtration (RO) is a process in which tap water is forced through a very fine membrane to remove contaminants.

Reverse osmosis water filtration systems combine an RO membrane with a series of other water filters to remove as much as 99% of all sediment, chemicals, colors, and odors from your tap water.

You can learn much more about reverse osmosis water filtration and how it works on our best reverse osmosis filter systems page.

What is Tankless Reverse Osmosis?

There are quite a few big differences between the tankless reverse osmosis systems in this review and “traditional” undersink RO systems with a storage tank…

Tankless Reverse Osmosis Throughput

Reverse osmosis water filtration systems with a storage tank deliver drinking water very quickly from a full pressurized tank. This is great for a single glass of water or if you want to connect the system to the water line of your ice maker.

Unfortunately, after you have drained the storage tank, the water pressure drops considerably and you have to wait for the system to slowly produce more filtered water.

The tankless reverse osmosis water filters on this page use an internal booster pump to filter water in real time at a high consistent rate. They also filter much higher gallons per day (GPD) than non-tankless systems.

Unfortunately, the booster pump does not provide immediate pressure and these systems don’t work well when connected to ice maker in your refrigerator.

Tankless Reverse Osmosis Efficiency

The process of reverse osmosis water filtration “wastes” tap water by flushing a percentage of processed water containing all of the filtered contaminants down the drain.

Because of their internal booster pumps and high-throughput filters, tankless reverse osmosis drinking water systems are extremely efficient. The RO systems on this page produce between 1 and 2 gallons of filtered drinking water per 1 gallon of waste water.

Compare this to traditional RO systems that waste up to 4 gallons of tap water to produce one gallon of filtered water!

You also don’t have to worry about your tap water pressure when there is a booster pump to maintain optimum pressure.

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Tankless System Size

Tankless reverse osmosis drinking water filtration systems are less than half the size of RO systems with a tank. If you store other things under your kitchen sink, then you will appreciate having more space available.

Smart Features

Tankless reverse osmosis water purification systems have many “smart” features that provide valuable information about your water and the status of the system.

All of these water filter systems have filter life indicators that remind you when it’s time to replace a filter. Efficient filters are critical to clean filtered water, so it is important to follow the manufacturer’s recommended schedule.

An extension of the filter indicators is a “smart faucet” that has an LED right built in. When the system is working normally, the LED will glow blue or green and if there is a problem, including the need to replace a filter, the LED will glow red.

TDS (total dissolved solids) is a measure of how much non-water (including contaminants) there are in your water. Some of these systems include a TDS meter that continuously tests your water and reports on the level of your filtered water.

All of these smart features are possible because tankless revers osmosis water filters require a 110V power connection, which most traditional water filters don’t have.

Easy Installation and Maintenance

Tankless drinking water filtration systems are easier to install under your sink because almost everything is contained in one case. There are fewer connections and less components.

Also, tankless water filters are super simple to replace without shutting off any water lines, using extra tools, or difficult access angles.

All of our recommend best tankless reverse osmosis systems have easy twist and replace filters right in the front of the case and you can expect almost no water drips during the filter replacement process.

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No Secondary Pollution

One last benefit is the prevention of secondary pollution from the storage tank.

While uncommon, the storage tank in other reverse osmosis water filtration systems can become a breeding ground for bacteria that will contaminate your filtered drinking water.

Tankless systems don’t have this problem!

Tankless RO vs Storage Tank RO Systems Comparison

 
Tankless RO
RO with Tank
System SizeSmallLarge
Speed and GPDHigh to Very HighLow to Medium
Waste WaterLow to MediumMedium to Very High
Booster PumpAlwaysRarely
Filter Life IndicatorsAlwaysNever
"Smart" FeaturesOftenRarely
Ease of MaintenanceEasyMedium to Difficult
Powers ice maker wellNoYes
Requires PowerAlwaysSometimes

Waterdrop G3 Reverse Osmosis System

Waterdrop G3 RO System
Waterdrop G3 Reverse Osmosis System

The Waterdrop G3 is a powerful NSF-certified undersink reverse osmosis drinking water system that provides the most smart features of any tankless RO system.

Read our full review of the Waterdrop G3 water purification system.

Waterdrop G3 Pros

  • The only NSF/ANSI 58 certified tankless reverse osmosis system
  • Smart faucet alerts you when the filters need changing
  • Real-time TDS readings on front of system
  • Integrated leak detector in system body

Waterdrop G3 Cons

  • 1:1 waste water ratio is good but not great
  • More expensive than competing systems
  • Taller than competing systems and may not fit under all sinks
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Frizzlife PD600-TAM3 with Alkaline Remineralization

The Frizzlife PD-600-TAM3 is unique because it comes with an alkaline remineralization filter that adds essential minerals back to the filtered water and raises the pH to more than 7.5.

Read our full review of the Frizzlife PD600 water filtration system.

Frizzlife PD600-TAM3 Reverse Osmosis with Remineralization
Frizzlife PD600-TAM3 Reverse Osmosis System

Frizzlife Pros

  • The only tankless reverse osmosis system with an alkaline remineralization stage
  • Real-time TDS readings on front of system
  • Very good 1.5:1 ratio of filtered drinking water to waste water
  • 600 GPD filtering is the fastest available

Frizzlife Cons

  • No smart faucet but still has filter life indicators on system body

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Buy or More Info

NU Aqua Tankless 600 Reverse Osmosis System

The NU Aqua Tankless 600 RO water filter hits the sweet spot of excellent performance, nice features including a smart faucet, and an average price among the tankless reverse osmosis competition.

NU Aqua Efficiency Series Tankless 600GPD Reverse Osmosis System
NU Aqua Tankless 600 Reverse Osmosis System

Read our full review of the NU Aqua Tankless 600.

NU Aqua Pros

  • Smart faucet alerts you when the filters need changing
  • Excellent 2:1 ratio of filtered drinking water to waste water
  • Shortest tankless reverse osmosis option that should fit under most sinks
  • 600 GPD filtering is the fastest available
  • 5 year warranty when registered online is longest of any tankless reverse osmosis system

NU Aqua Cons

  • No integrated TDS meter
  • Fewer stages of filtration than competing systems

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Buy or More Info

Waterdrop G2 P600 Reverse Osmosis System

Waterdrop G2 P600 Reverse Osmosis
Waterdrop G2 P600 Reverse Osmosis System

The Waterdrop G2 P600 system has fewer smart features than the G3 but more throughput and a much cheaper price tag.

Read our full review of the Waterdrop G2 P600.

Waterdrop G2 Pros

  • The least expensive recommended tankless RO system
  • Excellent 2:1 ratio of filtered drinking water to waste water
  • 600 GPD filtering is the fastest available

Waterdrop G2 Cons

  • No smart features except for filter life indicators on system body
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You may also be interested in:

Our top rated accessories for this or any other RO water system will help you customize your installation!

Compare these tankless drinking water systems with all other undersink reverse osmosis in our reviews and guide to the best undersink reverse osmosis systems.

If you like the idea of tankless reverse osmosis water filtration systems and want even more installation flexibility, check our our reviews of the best countertop water filtration systems.

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