Best Tankless Reverse Osmosis Systems

Image Product Editor’s Comment Rating Get The Best Deal
Waterdrop G3P800 Most Recommended Option

1. Faster water flow (800 gallons per day).
2. Certified against NSF/ANSI Standard 58 for TDS reduction.
3. 30-Day Return No Questions Asked Policy.

9.7/10 Check Current Price
NU Aqua Efficiency Series Tankless Reverse Osmosis System Most Elite Option

1. One of the Most efficient RO systems, drastically cuts down on waste water.
2. No messy filter changes. Just twist & remove the old filter and install the new one in less than 20 seconds.
3. Tankless design provides unlimited water on demand.

9/10 Check Current Price
Frizzlife Tankless Reverse Osmosis System Most Budget-Friendly Option

1. Composite pre-filter and RO membrane with highest filtration precision at 0.0001 microns.
2. Innovative tankless design to safe space.
3. Low drain ratio and ultra long service life.

8.5/10 Check Current Price
Waterdrop D6 Most Environmental-Friendly Option

1. 2:1 low drain ratio. More pure water but less waste water to save your water bills.
2. Advanced composite under sink reverse osmosis filter with 6-stage fine filtration, it can reduce 1000+ harmful substances.

8/10 Check Current Price


Why Invest in The Best Tankless Reverse Osmosis System?

Though many people reside in places where tap water is safe to drink, a much larger number do not. Due to this, consumers are compelled to buy distilled or purified water from a nearby company or grocery shop.

In either case, it will cost money, and it isn’t acceptable to constantly spend money on something as essential as water. But you can create potable water right from your local tap water with the best tankless reverse osmosis systems.

Pure, drinkable water is produced via the water distillation process known as reverse osmosis. Reverse osmosis distillation is a pretty common technique, and you can simply purchase a system that uses it to prepare tap water for consumption. These systems don’t have tanks, so if you want to have a lot of water on hand at once, you’ll need to keep it in containers.

Our article today will review the best tankless reverse osmosis systems available for you to purchase, as well as other important information on reverse osmosis systems that you need to know.

Best Tankless Reverse Osmosis Systems You Can Buy

Waterdrop G3P800

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One of the best tankless reverse osmosis systems currently on the market, the Waterdrop G3 stands out for its smart and practical features.

It has a faucet with a filter-change indicator light and a useful reminder that lets you know when your filters need to be changed. A TDS metre informs you of the number of impurities eliminated from your water, demonstrating that the filters are functioning properly. There are three filtration stages on the G3 water purifier:

The water filter includes a post-activated carbon filter to get rid of any lingering impurities, a RO filter to get rid of total dissolved solids (TDS), and a polypropylene (PP) cotton and carbon block filter to get rid of silt, chlorine, and lead.

Installation of the G3 takes only 30 minutes. You can put it on holiday mode while you’re away to prevent filter problems during this period. The system uses significantly less energy than most RO systems because it produces pure water and wastewater at a ratio of 1:1.


  • This system includes three different filters that are each home to seven filtration stages. A sediment pre-filter, a carbon post-filter, and a 0.0001 micron RO membrane make up the filter stages. The RO membrane eliminates 99% of all TDS.
  • The only tankless RO unit with an inbuilt UV purification filter that can destroy microbiological pollutants like viruses and bacteria is the Waterdrop G3P800.
  • The Waterdrop G3P800 has a highly effective 3:1 pure water to waste water ratio despite its comprehensive filtration.
  • Even the busiest household may utilise this machine, which can create up to 800 gallons of filtered water daily.
  • This Waterdrop model has a lot of smart features, such as a built-in TDS metre to show you how well the system is functioning and an LCD ring that changes colour to show you how the filters are doing.
  • Since the filters can be changed from the front of the device, which is only 5.7 inches wide, you won’t need to remove the housing for maintenance.


  • You’ll need a sizable budget for the Waterdrop G3P800 because it is, as expected, more expensive than rival filters.
  • Despite the faucet’s strong flow, a tank-based reverse osmosis system will provide clean water more quickly.
  • The alkaline filter is available separately for an additional fee if you want to remineralize your water.

NU Aqua Efficiency Series Tankless Reverse Osmosis System

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The NU Aqua Tankless 600GPD reverse osmosis water filtration system (WU-600GPD-TL) has been introduced to NU Aqua Systems’ already remarkable lineup as part of the tankless movement.

The NU Aqua tankless RO system has an excellent 2:1 pure water to waste ratio and can process 600 GPD, compared to the 100 GPD of competitive tankless systems and the 100 GPD of conventional undersink RO systems.

The NU Aqua Tankless RO system has almost all of its components in a single box, including 4 stages of filtration. This keeps everything more neater under the sink than traditional RO systems, where everything is exposed! Just 5 straightforward connections, all of which are easily situated on the rear top of the case, connect everything—the power supply and faucet are the only components that reside outside of the main body.

Anyone with basic DIY abilities may install the reverse osmosis systems from NU Aqua under the sink. Installation does not require a licenced plumber. Drilling a hole in the sink or countertop for the filtered water faucet is the only aspect of the entire installation that can be challenging. If a hole for a hand sprayer, soap dispenser, or blank cover is already present, this may not be required.

The majority of competitive systems come with a 1-year or even 3-year warranty. All RO systems from NU Aqua Systems come with a complete 5-year guarantee, during which time any damaged parts will be replaced.

Additionally, they provide a 120-day risk-free home trial. If you don’t enjoy it after using their system for 120 days, you can return it!


  • With four stages of filtration that can remove a variety of impurities, including VOCs, chlorine, rust, and suspended sediment particles, the NU RO filter offers an effective and efficient water filtering solution.
  • This system has three filters: a RO membrane that filters out salts, heavy metals, nitrate, and other contaminants; a polypropylene/carbon block filter that filters out sediment and chlorine tastes and odours; and a granular activated carbon filter that absorbs chemicals and flavours.
  • This machine operates more effectively, using just 1 gallon of water to generate 2 gallons of filtered water.
  • You’ll be happy to know that this system is 25% smaller than a conventional under-sink reverse osmosis system if you value your under-sink space.
  • You are not taking a chance when you purchase this system because the NU RO filter is covered by a 120-day money-back satisfaction guarantee.
  • The NU Aqua Efficiency Series makes filter replacement simple; simply remove the front cover and twist the filters in and out of position. The GAC filter lasts one year, the RO membrane lasts 36 months, and the PP/CB filter lasts up to six months.
  • There is no waiting around with this system’s impressive 600 GPD (gallons per day) flow rate.


  • You’ll require a sizable budget to be able to purchase the item because of its high cost.
  • Since the NU RO filter is not NSF certified, there is no independent assurance that it performs as promised.
  • The most intelligent tankless RO system available today is not this one.

Frizzlife Tankless Reverse Osmosis System

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The Frizzlife Tankless RO System has seven filtration techniques to provide nearly TDS-free alkalized water: sediment filter, carbon block filter, reverse osmosis membrane, remineralization filter, and weak alkaline filter.

This cutting-edge tankless reverse osmosis system may conserve up to 450% more water than a conventional under-sink filtration system and has a low drain ratio. The filter may be changed by simply taking out the old filter and clicking in the new one.

The unit also requires less effort to install. In contrast to other systems, the Frizzlife increases pH levels by reintroducing calcium and magnesium, enhancing the water’s health benefits.

Alkalinized water has health advantages and is superior to the water produced by conventional RO distillation techniques. Additionally, it has a low drain ratio of 1.5:1 and has no tank, so your kitchen and cabinets underneath will have plenty of room to spare.

The LED display, which provides real-time information about your filter and notifies you when to change it, is arguably the greatest feature.

The fact that RO system water is slightly acidic and, much worse, has little to no minerals is one of its key downsides. Since the membrane removes all impurities, even healthy minerals that would have been good for your health are removed. The Frizzlife contains a remineralization filter that is attached to the main device to gently alkalinize the water in order to address this issue.


  • The Frizzlife Tankless RO System combines seven deep filtration techniques to produce water that is almost entirely TDS-free and alkaline. These techniques are contained within a sediment filter, a carbon block filter, a RO membrane, a remineralization filter, and a weak alkaline filter.
  • This cutting-edge tankless RO system eliminates a variety of pollutants, such as cysts, chlorine and chloramine, lead, chromium, fluoride, arsenic, and organic and inorganic pollutants.
  • The tankless, space-saving design of the Frizzlife unit allows for up to 60% space savings.
  • With its extremely low drain ratio, the device can help you save up to 450% more than you would with a conventional under-sink tankless reverse osmosis system.
  • Additionally, it is considerably simpler to install, and replacing the filters only requires that you twist out the old one and click in the new one.
  • The device restores vital minerals to your water and raises pH, enhancing its health-promoting qualities.


  • One of the most expensive tankless reverse osmosis units currently on the market is the system.
  • The supplied faucet has drawn criticism from customers for being somewhat fragile.
  • It was produced in China. Customers concur that having the product created in the US would be preferable.
  • When the system is turned on, the motor hum is fairly audible.

Waterdrop D6

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The ratio of pure to contaminated water is 2:1, which is the best among all of its rivals. Consequently, purchasing this filter will benefit the environment. Additionally, it features a smart display faucet that displays the TDS value and the lifespan of the filters.

The Waterdrop D6 RO filter uses five different composite filters to purify water of hazardous impurities. Large visible particles, organic matter, salt, lead, chromium, and benzene levels are decreased, and chlorine flavour and odour are improved as the water goes through six layers. Additionally, this lowers the water’s TDS concentration.

This filter is also really easy to fix because it comes with all the necessary wiring, attachments, and instruction booklet. You can handle everything on your own; no plumbing assistance is needed. There are no particular maintenance requirements for this 6-level filtering system. It won’t need replacing for at least a year if you adhere to the apparent dos and don’ts.

600 gallons of water can be filtered via it each day. Compared to its rivals, this capacity is by far the best. There is a 0.42 GPM flow rate (gallons per minute). A glass of water can be filled in only a few seconds with this flow rate.


  • The contaminants that are removed by this Waterdrop drinking water filtering system include chlorine, lead, salt, nitrates, chromium, and more. The system incorporates a single filter cartridge with two cotton polypropylene layers, an activated carbon block layer, a reverse osmosis membrane layer, and a post-activated carbon block layer.
  • This RO system should provide enough drinking water for the entire household, providing up to 600 gallons a day.
  • The Waterdrop filtration system requires less maintenance because it is simple to install and the filter cartridge has a respectable 1-year filter life. The intelligent faucet displays the TDS level and remaining filter life in real-time.
  • The device features an outstanding wastewater to pure water ratio of 1.5:1 and a quick flow rate of 600 GPD. The fact that this system only requires a single filter cartridge makes it more economical at first.
  • The drain ratio of the device is an amazing 1.5 gallons of pure water to 1 gallon of effluent.


  • When in use, the Waterdrop D6 makes a lot of noise.
  • Even though you only need to replace one filter, doing so is expensive.
  • The unit’s back requires you to replace the filter, which is less practical than the front-loading filters on the Waterdrop.

Buying Guide For Tankless RO Systems

I’ve covered all you need to know in the buyer’s guide below if you’re interested in learning more about tankless RO systems before deciding if they’re the correct choice for you.

What is a Tankless Reverse Osmosis System?

The only difference between a tankless reverse osmosis unit and a typical reverse osmosis system is that the former does not utilize a tank.

Before usage, purified water from conventional reverse osmosis systems is stored in a tank. This implies that you don’t have to wait for the water to finish filtering through the RO system before you can drink it; instead, you may immediately get filtered water when you open the faucet.

Although tankless RO systems lack a tank, they nonetheless operate just as well. Many tankless RO systems are quick, filling a glass with filtered water in less than 10 seconds, and thanks to their tankless design, they take up significantly less room.

How Does A Tankless RO System Work?

The entire RO procedure is the same in a tankless RO system. The only major difference is that water is filtered on-demand rather than entering a tank after it has already been filtered; it then flows directly through the tankless system and out of the faucet.

A sediment pre-filter, an activated carbon or carbon block filter, and a semi-permeable reverse osmosis membrane are typically included in this kind of tankless reverse osmosis system. Some tankless RO systems additionally include a post-filter that gets rid of any remaining impurities or a remineralization filter that adds healthy minerals back into the water and makes it more alkaline.

To forcefully push water through each filter step, a high pressure is necessary. The RO membrane eliminates the bulk of the total dissolved solids, while the pre-filter removes suspended solids. The carbon filter removes pollutants like chlorine and pesticides (TDS).

Small pores in the semi-permeable membrane, typically 0.0001 microns or smaller, serve as a barrier to most pollutants. These contaminants eventually return to the RO chamber and are removed by a little amount of wastewater.

Next, assuming the tankless water filtration system has one, is the post-filter and/or mineral filter. After passing through these processes, the water will be sent directly out of the system’s designated faucet and be prepared for consumption.

Advantages of Tankless Systems

The following are some benefits of tankless reverse osmosis systems:

Space-Saving Design

A tankless RO water filtration system is the logical solution if space is at a premium. Most tankless RO systems are small enough to store in the corner of a cabinet without taking up valuable space, as there is no storage tank to take up space underneath your counter or kitchen sink.

On-Demand Water Filtration

Any bacteria or other microbiological pollutants that may have accumulated in the water while it was being held in the tank must be removed by an additional filter in traditional RO systems with a water storage tank.

With a tankless RO system, there is no risk of this contamination because the device offers immediate, on-demand water filtering. Additionally, there is no chance for secondary pollution.

Fewer Individual Filter Changes

Tankless RO systems frequently include fewer filter cartridges because of their small, space-saving designs, or they may combine many filter stages into a single cartridge. This reduces the number of individual filters in the water filtration system that need to be changed, which is a benefit if you want to perform as little maintenance as possible.

More Economical

To keep the storage tank full at all times, a tank-based reverse osmosis water filtration system creates a continuous flow of water. Since tankless RO systems only create cleaned drinking water when it is truly needed, they are more cost-effective.

By using an at-home RO filtering system, you may decrease your own plastic waste and save money on bottled water. Most tankless RO systems also don’t require a power source to operate.

Improved Water Taste

The flavour of water that has been provided directly from a smart faucet is superior to water that has been sitting in a storage tank. When you need it, tankless RO systems deliver clean, fresh drinking water.

Better Smart Features

The best tankless RO systems currently on the market come with a number of innovative features that are uncommon in tank-based systems. For these water filters, a built-in TDS reader and a smart faucet with a filter life indicator light are both very useful.

Easier to Install & Maintain

Tankless RO water filters often require less than 30 minutes to install because they just have one unit.

While installing a whole-home or under-kitchen-sink tank-based system might require hiring a plumber, most tankless designs are straightforward enough for do-it-yourselfers. A feed water adapter is a common feature of RO filter units, preventing leaks during installation.

Most tankless systems make it much simpler to change the filters. Simply remove the outdated filter and install a fresh one after opening the appliance.

Disadvantages of Tankless Systems

It’s important to be aware of the following tankless RO water filtering system drawbacks:

More Expensive

Tankless RO water filters are often more expensive than traditional RO systems with a tank because of the benefits of their on-demand, space-saving water supply. For one of these water filtration systems, you should be prepared to shell out at least $450. Some even have a $600 price tag.

Still Quite Inefficient

Even though tankless RO water filters are made to be more effective and less wasteful, they nevertheless use more tap water than other types of water filters during the reverse osmosis process. If you object to paying extra money to use water that you don’t actually get to drink, this may irritate you.

May Take Slightly Longer to Deliver Water

As I’ve already indicated, tankless reverse osmosis systems offer filtered drinking water quickly, but before the water can reach the smart faucet, it must pass through every single RO filtration stage, including a potential remineralization filter.

This implies that compared to a system with a tank, you’ll probably have to wait a few extra seconds for high-quality drinking water from this system.

No Water Storage in Emergencies

If an emergency arises and your water supply line is cut off, a tank-based RO system will give you access to a batch of clean, filtered water. When you turn on your faucet (or the associated smart faucet), a tankless unit can only create clean water, thus it doesn’t provide this benefit.

Considerations When Buying a Tankless RO Filter

Think about the following points before purchasing a tankless reverse osmosis system:

Incoming Source Water

With a tankless reverse osmosis system, the source of your incoming water is less crucial because most RO water filtration systems can already remove more than 99.9% of all TDS from water.

However, if you are aware of the precise contaminants that you want to get rid of, you may choose the best RO water filter system for your needs depending on what contaminants the filter is designed to get rid of.

Before investing in a RO system, I advise testing your water to identify the pollutants that are most prevalent.

Water Pressure

Most tankless reverse osmosis water systems have less of an impact on your incoming water pressure than a whole-house system would.

A water pressure range between 15 and 85 psi is needed for the majority of tankless reverse osmosis drinking water filtering systems.

The water flow rate through your RO water filter may, however, be slower if your water pressure is on the lower end of this range, particularly at the reverse osmosis membrane. This could generate a slower stream of cleansed drinking water and more waste water than is necessary.

Purchase a booster pump to easily fix low water pressure. Your water pressure can be increased by a booster pump to a steady level, enabling your RO system to function faster.

Occasionally, you can upgrade your initial RO purification system purchase by purchasing a booster pump. Otherwise, they are accessible on the majority of web markets.

Produced to Wastewater Ratio

Compared to conventional under-sink models, tankless RO systems have a higher pure water to waste water ratio.

For every 1 to 1.5 gallons of pure water generated, a tankless purification system may only produce up to 1 gallon of waste water. You’ll waste less daily tap water and spend less money if this ratio is better.

Flow Rate

Water pressure and flow rate are partially related, however depending on the design, a tankless reverse osmosis system may purify your tap water at its own measured flow rate, regardless of your water pressure.

An RO system must have a good sediment filter that is capable of removing big particles that could obstruct later filtration stages and delay the flow of tap water.

As the filters near the end of their useful lives, the flow rate will also inevitably decrease. 400 gallons of water per day should be the maximum flow rate that RO systems can provide. Even up to 600 gallons per day of flow are available from some systems.

Remineralization Needs

Reverse osmosis water filtration systems are exceptionally efficient and can virtually eliminate all impurities from your water. The issue with this filtration method is that it also removes helpful contaminants, including healthful minerals.

Remineralization filter stages, which inject minerals back into the filtered water and raise its alkalinity, are now being offered by an increasing number of tankless reverse osmosis machines. You get to enjoy pure, clean drinking water that still includes beneficial minerals and tastes better as a result of this.

Before choosing a new RO system, think about if you’re interested in using an alkaline remineralization filter because it’s not necessary. If you want a RO filtering system with a built-in remineralization stage, your options will be more constrained, and the system will probably cost more than other systems.

As an alternative, you might decide to add mineral drops to your water before consuming it. By doing this, you’ll still have access to a wider range of RO filter systems and won’t need to worry about purchasing additional replacement filters.

Filter Lifespan

Reverse osmosis drinking water systems without tanks frequently employ the same kinds of filters as conventional under-sink systems, so you can anticipate that their filter life will also be generally comparable.

Three filters need to be changed, so keep that in mind. A semi-permeable membrane typically has a filter life of two years. Pre-filters typically have a lifespan of 6 to 9 months, while RO carbon filters have a filter life of around 12 months.

Finding a RO water purification system with a smart faucet and filter life indicators will eliminate the guesswork associated with filter changes and guarantee that you always have access to fresh water.

Space Available for Installation

The space-saving advantages of a RO system without a tank are probably your main reason to get one. This type of system requires less space than conventional tank-based rival systems, however not all tankless RO units do so equally.

It’s crucial to thoroughly measure the area you have available and compare those figures to the specifications of a unit you’re considering. Even though the majority of units are thin, some may be too tall for your cabinet or under-sink area. Remember that in addition to the unit itself, you will also need room for a waste line and possibly a special RO faucet.

Do the measurements before you buy anything to avoid the headache of having to return a system that won’t fit in your space.


Manufacturers of reverse osmosis systems can submit an application to NSF International, an independent agency that tests, inspects, and certifies food and water consumer products, just like most drinking water filters in the US.

An RO system may be certified by NSF in a number of ways:

  • NSF 58

The certification specifically for reverse osmosis systems is NSF 58. A system can remove total dissolved solids to the advertised level and offers the high level of performance required from a RO unit if it has an NSF 58 certification.

  • NSF 53

In order to remove heavy elements like lead, arsenic, and mercury, reverse osmosis systems are frequently certified to NSF 53.

  • NSF 372

Manufacturers can receive the NSF 372 certification if they can demonstrate that their system complies with lead compliance requirements (i.e., that it isn’t constructed with materials that can cause lead to leach into water).

Tankless Reverse Osmosis Water Filter Maintenance

Reverse osmosis systems without tanks require little maintenance. The only maintenance required is filter replacement, which is simpler to carry out than with a conventional under-sink system.

How frequently you must replace the filters will depend on the specific RO system you choose. Additionally, some systems may have more filters than others. For instance, one system can have an all-in-one filter that needs to be changed only once a year, while another might have three separate filters as well as a remineralization filter with different lifespans.

Make sure you’re happy and dedicated to this maintenance work before you make a purchase because you should anticipate having to replace your filters at least once a year.

The frequency of filter replacement for your RO system will depend on how much water you use. The filters will clog and wear out more quickly the larger your family or the more water you consume.

On the other hand, if you live alone and only use the water in the mornings and nights, your filters may last considerably longer than they were intended to.

I advise purchasing a RO system with a built-in filter life indicator if you’re unsure that you’ll remember to change your filter. When your filter has to be modified, this will change colour to let you know.

Frequently Asked Questions

How Does a Reverse Osmosis Water Filtration System Work?

In order to comprehend water filtration, it is important to define the scientific word osmosis. Osmosis is the process by which a solvent, such as water, diffuses into a solution with a higher solute concentration through a semipermeable membrane, such as a living cell.

The reverse of osmosis is the idea behind a tankless reverse osmosis system. Water filters assist in reducing the concentration level and supplying water that is less concentrated, as opposed to creating more concentrated water.

The common pollutants found in tap water from public utilities or private wells are removed by pressurising the water and forcing it through filters.

Which is Better: A Tank or Tankless RO Water Purifier?

Reverse osmosis (RO) water purifiers for the house come in two basic varieties: those with a drinking water storage tank and those without.

drinking water reservoir The usage of a tankless RO water purifier eliminates the need to wait for the drinking water container to fill up before utilising the filtered water that RO water purifiers deliver at your convenience.

Filter dealers have introduced an enhanced reverse osmosis system with huge storage capacity—and no tank—as the need for cleaned water rises with an improved standard of living.

This drinking water filtration system’s key selling point is that it does away with the pressure container, which frees up less room under the sink and gets rid of any contamination that the storage tank might have introduced.

How much wastewater do reverse osmosis systems produce?

Although tankless reverse osmosis system is a widely used method for water purification, it wastes a lot of water.

Each model of a tankless reverse osmosis system has a different waste ratio. However, a tankless reverse osmosis system typically produces three gallons of wastewater for every gallon of clean water.

Will RO filters remove minerals from my water?

Some water filtration systems filter the water while keeping some good minerals, however most systems remove a variety of chemicals from the water, including harmful minerals. Minerals from tap water are not taken out by ceramic and activated carbon filters.

Chlorine, VOCs, THMs, and other organic contaminants can be removed from water using carbon filters, however minerals, salts, heavy metals, etc. cannot.

To compensate for various drawbacks of carbon filtration, ceramic filters are sometimes utilised in home water filtration applications (e.g., carbon is not enough to remove viruses and other pathogens from your tap water; thus, ceramic is used).

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