5 Best Tankless Reverse Osmosis Systems – Tested and Reviewed

A reverse osmosis system is a great way to produce healthy water at an affordable price. Drinking RO water is cheaper than buying bottled water. It fits the most critical requirements for residential water demands.

And tankless RO system helps you avoid secondary pollution. It also lets you enjoy more space in your kitchen.

But choosing the best tankless reverse osmosis system is a daunting task. As it’s a long term investment, you need to be extremely sure which model will best meet your immediate and long-term needs.

But worry not!

After conducting thorough research and testing several models, our water experts team has short-listed 5 reliable models.

Go through our tankless reverse osmosis system reviews to discover them.

Best No Tank Reverse Osmosis System – Our Top Picks

Check out the following quick overview to compare all the essential specs of these 5 best-selling products at a glance.

  • Best Overall: Waterdrop WD-G3-W: A water filtration system that offers excellent performance, saves water waste by 300%, improves water taste, and saves money on your water bills.
  • Best Space-Saving: iSpring RO500: Features a no-tank design, thus frees up more space in your undersink storage area and adds aesthetics to your kitchen.
  • Best for Large Families: Frizzlife PD600-TAM3: With a high capacity of PD600 and fast water flow rate, this device can meet the daily pure water needs for your big household.
  • Best Smart: PURLETTE PL400G: Track filter life and filtered water quality with your voice when using this next-generation water treatment device at your home.
  • Best for Small Households: Greatwell ROG400 : Rated at 400GPD and a water flow rate of 0.4 gallons per minute, this system will sustain your small family’s daily needs for pure water.

Best Tankless Reverse Osmosis System Reviews

We aim to recommend you the best no tank RO system for home to ensure that you enjoy safe and healthy water to prevent adverse health effects.

We hope this list and reviews will be helpful for you to find the best one that will meet your needs.

 Let’s get started!

1. Waterdrop WD-G3-W RO Drinking Water Filtration System

Waterdrop WDG3

We start our review with one of the trustworthy water purification solutions, WD-G3-W, from a well-known and professional water filtration brand Waterdrop.

WD-G3-W is an all-in-one, innovative, and smart RO drinking water filtration system. It’s the first smart reverse osmosis system in the U.S market that comes with a tankless design and composite filters.

So, what makes the Waterdrop WD-G3-W stand out?

The unit uses new composite filter element technology to more efficiently filter out harmful elements from water.

It comes equipped with three filters that provide seven stages of filtration. It excels at preventing 1000+ contaminants, including fluoride, limescale, and heavy metals in your tap water. Moreover, the system is certified against NSF 58 for 94% TDS reduction.

The included pre-sediment and carbon-block filter act 3-in-1 filter combined.  Besides, the efficiency of the RO membrane is equal to or more than three-stage of filtration. It offers excellent filtration performance with a seven-layer RO membrane and with a filtration accuracy of 0. 0001μm.

Moreover, the activated carbon block filter improves the water taste. Thanks to its high-precision carbon granules which are all made from natural coconut shell.

Waterdrop RO system filters 400 gallons of water per day. It can deliver a cup of water for about 12 seconds. Thereby, it meets the needs of filtered water of your whole family and even a small office.

The drain ratio of this system is 1:1. That means it saves water waste by 300% compared to conventional RO water filter. Thus, it saves money on your water bills.

G3 RO System comes with several smart features such as auto shut-off reminders, automatic flushing, and filter life indicators. It also monitors water quality 24/7. This model includes an integrated water circuit to avoid leakage.

The tankless design makes it easy to install. You’ll require only 30 minutes for complete installation and only 3 seconds for filter replacement.

Conveniently, it comes included with a smart and lead-free faucet that has an indicator of water quality and filter service life. Most importantly, it’s NSF 372 certified for lead and BPA free material.


  • Tankless, compact design for more storage space in your kitchen
  • Faster water flow (400 gallons per day)
  • 94% TDS reduction
  • 99.99% contaminant removal
  • Easy installation and filter replacement
  • Economical and environmentally friendly
  • NSF Certified, UL Listed


  • It requires under-sink electricity.
  • Somewhat expensive

2. Frizzlife Tankless Reverse Osmosis System with Alkaline Remineralization – PD600-TAM3

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

Frizzlife PD600 provides the healthiest and greatest testing water to you.

Water produced by Conventional RO systems is slightly acidic and lacks in natural minerals. But this is not the case with the Frizzlife RO system.

The filtered water by this model is well-balanced for alkalinity. It also adjusts the pH to more than 7.5. Importantly, it retains the beneficial health minerals to your filtered water.

You are guaranteed to provide safe and ultra-pure water for you and your family!

This three-stage filtration system uses a 2 in 1 composite filter in the 1st stage that blocks fine debris and particles. Thus it conditions water and prolongs the life of the RO membrane.

In the second stage, the high grade 0.0001 micron RO membrane removes 99.99% of the contaminants, including lead, VOCs.

Stage 3 involves restoring natural minerals, balancing the alkalinity of filtered water, and adjusting the pH. It also reduces the odor, bad taste, and polishes the flavor. Thanks to its alkaline remineralization filter (TAM3).

Get a full cup of freshwater in a snap!

The high capacity of PD600 can meet the daily needs of your large family. It adopts an internal prompt and produced 600 gallons of water per day. The water flow rate is stable and fast, filling a 330ml cup of water in about 10 seconds.

It pays for itself in water savings!

The advanced water-saving technology maximizes efficiency and makes it cost-effective. This model can save your water up to 460% compared with the traditional RO system.

Conveniently, the built-in TDS system monitors the quality of your drinking water 24/7. Of course, the color-coded indicators always remind you to replace the filters in advance.

Another stunning feature of this unit is its smart LED display panel that clearly shows real-time out TDS and the remaining lifespan of each filter.

The compact footprint of its housing takes less space under the kitchen sink. It’s worth noting that this model comes with filters inside and one lead-free faucet.

With well-organized step-by-step instructions and video and all included parts, you can completely install it in a few minutes.


  • Economical and environmental friendly
  • Reduce TDS & 1000+ contaminants
  • 0.01-micron filtration accuracy
  • Restores natural minerals and produces weakly alkaline RO water
  • Compact design; saves up to 60% of spaces
  • Less wastewater; save up to 450% of water than a conventional RO system
  • Integrated water line; no leaking worry
  • Easy installation & quick filter change
  • Clear instruction manual


  • It produces a slight hum sound when getting water.

3. iSpring RO500 Tankless Reverse Osmosis Water Filtration System

iSpring RO500

iSpring RO500 is one of the most advanced RO water filtration systems that overcome all traditional RO filters’ drawbacks.

RO500 is an under-sink RO system that features three-stage filtration. Featuring a sleek no-tank design, it not only frees more space in your under-sink storage area but also adds aesthetic pleasure to your kitchen.

It comes with a multi-layered composite filter as the first line of defense against polluted water that filters out dirt, rust, sand, particles, as well as chlorine, and odor.

This unit’s high-flow RO membrane is built specially to filter out 1000+ contaminants, including fluoride, lead, asbestos, arsenic, and more.

The Carbon block filter in the stage-3 flushes out residual dirt found in water and brings you odorless and tasty water.

Impressively low drain ratio!

RO500 is economical and ecological. It’s rated at 500 GPD, and the pure to wastewater ratio is 2:1, which saves water waste up to 400% compared to a conventional RO system.

One of the outstanding aspects of this model is its unbeatable performance.

The flow rate is up to 0.4 GPM, which is four times more efficient than any conventional RO unit.

This is not the end; there is more…

The included smart faucet will enhance your user experience. It features a real-time TDS with codes indicator that helps you monitor your water quality most conveniently.

Conveniently, its indicator displays the TDS of filtered water. Besides, the filter status indicator suggests a filter change schedule and shows codes to help trouble-shooting.

The installation of the RO500 is hassle-free. The re-inforced integrated water route design simplifies the installation process and eliminates leaking concerns.

Furthermore, you can easily change the filter without any water leakage or spill. Thanks to its tool-free twist and pull design.


  • Innovative, sleek Design
  • The convenience of filter change
  • Real-time water quality monitoring
  • Super filtration Performance
  • Industry-leading pure to wastewater ratio
  • Hassle-Free DIY Installation and filter replacement
  • Backed by a 30-day money-back and 1-year manufacturer warranty


  • Pricey, but it is well worth the investment.

4. PURLETTE PL400G Reverse Osmosis Water Filtration System


Purlette PL400G is world’s first smart hybrid water filtration system. It’s an elegant, convenient, and innovative water treatment solution that will clean and purify city tap water right from your kitchen sink.

You can rest assured that your family has access to refreshing and safe drinking water from the Comfort of your home.

This model removes suspended particles from hard water, stops scaling, and eliminates chlorine flavor from water.

The five-stage filtration system eliminates 99% of over 1000 contaminants and harmful impurities commonly found in tap water. It’s exceptionally efficient at Lead, Chlorine, Fluoride, and TDS reduction.

So, how is this achieved?

The hybrid dual filter design serves as the foundation of this system. It houses the first three filtering stages with sediment pre-filter, active carbon filter, and high precision PP filter.

The five layer RO membrane filters water deeply, which then returns to the hybrid filter again for the final step of post-carbon block filtration.

It can filter up to 400 gallons of tap water per day. The hybrid dual filter has more capacity but wastes less. In two years, this system requires three filters only, equivalent to the use of 13 filters in the traditional RO system.

It’s worth noting that you may need to replace the hybrid filter every 12 months and the RO filter every 24 months for a family of four members.

What’s more, this unit has leak protection. At the first sign, if any leakage, it’ll cut off the system’s water supply.

With this next-generation water treatment device, you can use your voice to check filtered water quality and track filter life. 

Finally, it comes included with one satin nickel finished faucet. Importantly, it’s BPA and lead-free.


  • UL, NSF, FCC tested and certified for effectiveness and safety.
  • All in one space-saving design
  • Easy to fit under any standard size kitchen sink
  • Smart and convenient design
  • Real-Time monitoring of TDS levels and high TDS alerts
  • Designed for easy installation and DIY maintenance


  • Designed for filtering city water only with a TDS level of less than 500. If you plan to use it for well-water, you have to install a pre-treatment device on the water source.

5. GreatWell ROG400 Reverse Osmosis

GreatWell ROG400 Reverse Osmosis

Greatwell ROG400 is a new generation RO system that transforms your tap water into purified drinking water on demand. Whether you have bad taste in tap water or safety concern, this unit is perfect for solving your drinking water problems.

It removes all harmful elements from your drinking water far beyond EPA standards.

Greatwell’s PAC filter is a 3-in-1 carbon wrap filter. It works as a combination of two sediment filter and a carbon filter. This aspect saves more than 30% of space within the housing and cost of filter replacement in the long term.

PAC composite filter removes rust, sand, chlorine, etc. from tap water. Additionally, the active carbon polishes water to ensure water taste and quality.

Besides, the precise RO membrane removes up to 99% of over 1000+ harmful contaminants from water. This membrane is rated at 400GPD, and the water flow rate is 0.4 gallons per minute.

What’s more, ROG400has an impressive pure to wastewater ratio, which is 1.5: 1. That means, it could save more than 1000 gallons of water going into waste each year.

A leak-free integrated water route minimizes connectors and makes ROG400 installation a breeze. Additionally, snap-on filters and system cover makes filter replacement easy. Conveniently, it features a build-in true filter change indicator that monitors each filter’s life.

Of course, the all-in-one and no tank design provides more under sink or countertop space.

It’s worth noting that its vertical filter replacement design saves around 30% of space under the sink compared to a horizontal configuration.

You can rest assured that it is safe to use as all parts of ROG400 complies strictly with NSF/ANSI standards for water quality and safety.

Finally, you’ll applaud its included artisan-style stainless steel drinking water faucet.

Did we mention said that you could connect this system to the refrigerator or ice-maker?

You can do this.


  • Thoughtful, innovative design
  • Simple installation process
  • Easy to filter replacement and maintain
  • Superb water taste
  • Fast water flow
  • Tested by an independent 3rd party against NSF/ANSI standards
  • Backed by 1-year limited manufacturer warranty
  • Lifetime technical support


  • The installation instructions should be more detailed.

How to Choose the Right Tankless Reverse Osmosis System

No tank RO system produces water instantaneously, so this variation is ideal for both home use and small commercial purposes.

All the above-reviewed units are reliable to meet your need. But, before getting yourself one, you need to consider some factors to make the right fit.

The GPD/ Gallon Per Day

When buying an RO system, the first thing you should consider is its GPD rating. Check it is enough for your drinking water needs of your family. Higher GPD means higher performance. But if you have a small family, buying a unit with a higher GPD would a waste of money.

Filtration Stages

Another vital aspect to consider is filtration stages and the number of filters. This type of system uses the filter composition technology, which removes most of the contaminants in tap water. But based on the filtration stages that undergoes, the quality of filtered water may be different.

RO systems have three to five stages of filtration. However, some models incorporate two more steps and continue to give ultra-safe water for drinking.

You should look at how many types of filters the unit uses and the stages of filtration the product offers.

Don’t forget to check how long it works effectively before you need to replace the filters.

Efficiency and Low Water rejection rate

RO systems waste-water during purification. Its efficiency is summarized by a ratio of wasted water to pure water produced, indicated by the drain ratio.

Check the drain ratio and make sure the model you are going to buy is eco-friendly and cost-effective.

Ease of installation

Installing a RO system for home use is a simple DIY activity.

If you’re somewhat mechanical and handy, installing a no tank unit won’t be too difficult for you. Make sure the model you’re going to buy comes with clear installation instructions and a well-labeled diagram.

The Price

No tank RO units are pricey than the traditional RO system. But no-tank models deliver better-filtered water than regular RO models, and it will save you a lot by producing low waste-water. So, when water quality and safety are of concern, the price may be overlooked.

If you greatly value space-saving solution and instant filtered water, a no-tank variation might be a worthwhile investment for you.


Look out for the warranty when purchasing a unit. Note that the warranty laws may vary from state to state. So, buy one which warranty laws comply with the laws of your state so that you can enjoy the full benefits. In general, these systems come with a one-year warranty. Some also offer a money-back guarantee for the month.


To enjoy instantly filtered drinking water without the need for a storage tank, these above reviewed 5 best tankless reverse osmosis systems are unbeatable.

You can rely on any of these best-selling systems to meet your drinking water needs.

Pick one from our comprehensive list and enjoy purer and cleaner water at a lower cost!

When you buy something through our affiliate links, we earn a commission without you having to pay extra.