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Reverse osmosis (RO) systems are incredibly effective at removing large numbers of contaminants from your water supply as they use efficient RO membrane tech. The only issue is that whole-house systems tend to take up a fair bit of space and can be tricky to install. That’s why a compact countertop RO system that requires little installation can be such a good option.

In our list of the 4 best countertop RO systems, the AquaTRU Countertop RO System comes out on top. It’s the only system we reviewed that’s NSF certified which means its contaminant removal capabilities have been independently tested. Plus, it requires no installation and has a separable filtered water tank you can store in your fridge.

The runner-up is the RKIN U-1—the best option if you’re looking for hydrogen-enriched water. It also uses advanced RO filtration to remove contaminants and features a UV light to keep your stored water fresh.

For a more budget-friendly unit, we’d recommend the Waterdrop N1 at just 9.

Countertop RO Systems Comparison Table

1. AquaTru Reverse Osmosis Water System – Best Overall

AquaTru Reverse Osmosis Water System is the best overall reverse osmosis system because it offers 4 stages of RO filtration, 1-gallon water tank capacity, 4:1 waste water ratio, and the NSF certification to prove it’s effective against drinking water contaminants like lead, fluoride, copper, barium, radium, chlorine, and PFAS.

If you’re looking for a countertop RO system that requires no installation, is highly efficient, and uses a 2-tank water storage system, we’re sure you’ll love this unit’s features.

Advanced 4-Stage Filtration

The 4-stages of filtration are broken down as follows:

• Mechanical pre-filter: It prevents large particles like sediment from entering the system and hindering the filtration process.
• Activated carbon filter: It reduces the majority of aesthetic impurities like chlorine and chloramines, improves turbidity, and reduces the presence of chemicals and heavy metals, thus easing the work of the RO membrane.
• RO membrane: This highly effective RO membrane is responsible for the removal rates listed in the datasheet.
• Activated coconut shell carbon VOC filter: It’s designed to trap volatile organic compounds (VOCs) that might have escaped through the RO membrane.

This AquaTrue model can remove up to 99% of contaminants, making it one of the most effective RO systems we’ve tested. It was also excellent at removing bad tastes and odors from water and preventing faucets and appliances from staining.

2-Tank System

In addition to these 4-filtration stages, this system has two tanks: a 3-gallon tap water tank and a 1-gallon filtered water tank. Once you plug in the device and fill the tap water tank with water, you’ll start getting filtered water in a matter of minutes. What’s even better is that the filtered water tank is totally separable from the unit. So, on hot summer days, you can simply put the water tank in your fridge for cold, filtered water.

LED Indicators

When testing this unit, we found the LED indicators really helpful as they told us when it was time to replace the filters. We always take points off a filter system if it lacks a digital display, so we were pleased to see this included in this unit.

That being said, one downside is that the AquaTRU filters aren’t as long-lasting compared to the other options in this article. Depending on your usage, the LED display will likely inform you of a filter change in just 4 to 6 months.

2. RKIN U-1 – Runner-Up

The RKIN U-1 is the most versatile countertop RO system we tested while making this list. It combines RO filtration with a UV light to keep water fresh when not in use. Plus, it comes with an optional hydrogen filtration stage that creates hydrogen-enriched water, and it can also provide instant hot water.

So, we’d highly recommend it to anyone who wants a couple of useful extras for a fairly affordable price.

RO Filtration with A UV Light

The U-1 removes up to 99% of contaminants using a combination of an RO membrane with a sediment filter, an activated carbon filter, and an alkaline post-filter. Yet, that’s not all. One thing we liked about this unit is the fact it also comes with a UV light. This isn’t part of the filtration process but is used to keep water stored in the tank fresh when you’re not using the device.

This gives you access to clean and fresh water directly from the tank without having to wait for more water to be filtered.

Hydrogen Tech

The final stage of the U-1’s filtration process involves hydrogen infusion. This is optional and can be turned on and off via its control panel (which we’ll discuss in a moment). When you turn it on, the system provides antioxidant hydrogen-enriched water with several potential health benefits.

The reason this is such a welcome feature is that the RO process removes beneficial minerals as well as contaminants. So, by enriching the filtered water with hydrogen, the U-1 at least partly addresses this issue.

Intelligent Control Panel

One of the main reasons the U-1 is second on our list is its excellent digital interface. We found it really easy to use and all of the controls are clearly labeled with symbols and text, so it took no time at all to get the hang of it.

The panel gives you notifications about the condition of the filters, the TDS levels of your water, how full the supply tank is, and much more. Some of the most useful buttons on the panel include:

• A “Hydrogen” on/off button
• A “Small Cup” button for 5 fluid ounces of water
• A “Large Cup” button for 10 fluid ounces of water
• A “Milk” button which is used to dispense baby formula temperature water
• A “Hot” button for boiling water

In this area, the U-1 beats the AquaTRU unit hands down, and it came close to being top of our list.

3. NU Aqua 4-Stage System – Best Countertop RO System With Hot Water

Like the U-1, the NU Aqua countertop RO system delivers hot water, as well as cold water. This is thanks to the instant water heating system that allows it to operate efficiently with water temperatures higher than 77F.

Plus, if eco-friendliness is a priority for you, then you’ll be really impressed with its wastewater ratio—it produces 5 cups of filtered water for a single cup of wastewater.

Key Features:

• Full control: The NU Aqua countertop RO system directly filters tap water from the 1-gallon tank to its spigot and lets you choose how much water you want it to dispense on demand with 4 oz, 8 oz, 16 oz, and 32 oz options
• Effective filter cartridge tech: Like the Waterdrop N1 below, it has two different filter cartridges. The first cartridge has a sediment filter, which prevents large particles from entering the system, and a carbon block filter, which removes aesthetic impurities, chlorine, VOCs, chemicals, and bacteria like giardia. The second cartridge features a highly rated reverse osmosis membrane to filter chemicals, heavy metals, and TDS effectively. Lastly, the water passes through a granular activated carbon filter that removes whatever residue is left from the previous filtration processes.
• Eco-friendliness: Considering the efficiency of its RO membrane, the 5:1 wastewater ratio is all the more impressive, making it the most eco-friendly product in this article.
• Versatility: The NU Aqua countertop RO system filters both tap and well water, but with the condition that the original TDS levels of the well water should be below 500 ppm (parts per million). This is a huge bonus, considering that most portable reverse osmosis systems don’t filter well water.

4. Waterdrop N1 Countertop Reverse Osmosis Water Dispenser – Best Compact and Portable Dispenser System

The Waterdrop N1 has many of the same key features as the other systems on our list but it’s smaller, more portable, and has a more modest price tag. We really like how easy it is to carry! This is a great option if you’re looking for a filter to take on the road. For example, you could use it to filter water in your RV.

Key Features:

• 4-stage filtration: The Waterdrop N1 utilizes a 4-stage filtration process, which involves a PP cotton filter, a carbon block, an RO membrane, and a UV light. As with the NU Aqua model, the filtration process takes place in 2 cartridges instead of one cartridge
• Decent filter lifespan: One of the two cartridges houses the polypropylene sediment filter and carbon block, and this particular cartridge needs to be replaced once every 6 months. The RO membrane has a fairly longer lifespan of 18 months.
• Effective contaminant removal: The Waterdrop N1 is highly effective against contaminants. It reduces the presence of heavy metals, TDS, chlorine, nitrates, and aesthetic impurities to a great extent, providing healthy, clean, and great-tasting water.
• Good wastewater ratio: The N1 produces 3 cups of pure water for one cup of wastewater, which makes it an eco-friendly option (but not as eco-friendly as the NU Aqua system)
• LED display: Although its control panel isn’t as detailed as the U-1’s, it still allows you to monitor and control the system easily

Our Review Criteria for Countertop Reverse Osmosis Systems

We evaluated the countertop RO systems in this article based on the following criteria:

• Contaminants removed
• NSF certifications
• Water/filtration capacity
• Wastewater ratio
• Maintenance requirements
• Warranty
• Price

Contaminants Removed

The first aspect to look at when purchasing an RO system should be the system’s ability to remove common water contaminants like lead, chlorine, and PFAS. To scientifically determine how many contaminants a RO system removes, the device is tested by an independent lab. However, not all manufacturers bother to get their products tested or provide customers with test reports.

Of all the products we evaluated, only the AquaTru Countertop RO System comes with a performance data sheet prepared by an independent lab. This sheet shows that the unit can remove up to 82 contaminants with more than a 95% success rate.

Although the product pages for the NU Aqua and Waterdrop models claim that these units can remove more than a thousand contaminants, these claims aren’t supported by independent testing.

Countertop RO Systems	Contaminants Removed
AquaTru RO System	82
RKIN U-1	Not specified
NU Aqua 4-Stage RO System	Not specified
Waterdrop N1	Not specified

NSF Certifications

The National Sanitation Foundation (NSF) is a non-profit organization that tests and evaluates the health impact of products in various industries, from automotive parts to water treatment systems. NSF certifications assure customers that a manufacturer's health claims about their product are supported by scientific data.

However, most RO system manufacturers overlook the importance of these certifications, even though they can inspire trust in the customer base. Again, the only product in this article that holds relevant certifications is the AquaTru Countertop RO System:

• NSF/ANSI 42: It certifies that the device is capable of removing aesthetic impurities that affect the taste, color, and odor of water, as regulated under the National Secondary Drinking Water Regulations by the EPA.
• NSF/ANSI 53: It certifies that the device can reduce contaminants that have health effects as determined by the EPA-set National Primary Drinking Water Regulations (NPDWRs) in the case of the United States and Health Canada in the case of Canada.
• NSF/ANSI 58: Applying only to RO systems, it certifies that the device operates by properly pushing water through a semipermeable membrane.
• NSF/ANSI 401: It certifies that the device is capable of removing at least 15 of the emerging contaminants. Emerging contaminants, or contaminants of emerging concern, are those that aren’t aesthetic impurities but that are not yet regulated under NPDWRs by EPA either.

Countertop RO Systems	NSF Certifications
AquaTru RO System	NSF/ANSI 42, 53, 58, and 401
RKIN U-1	N/A
NU Aqua 4-Stage RO System	N/A
Waterdrop N1	N/A

Water/Filtration Capacity

There are two types of countertop RO filtration devices in this article: systems with a water tank (all of the units on our list), and those that are directly connected to a faucet.

For the former category, their water capacity indicates how much water the tanks can hold and filter.

The AquaTRU and NU Aqua systems are joint winners in the category as they can both hold a gallon of filtered water.  However, it’s worth noting that the AquaTru can hold 3 gallons of water in its tank for unfiltered water.

Countertop RO Systems (with tank)	Water Capacity
AquaTru RO System	1 gallon
RKIN U-1	0.5 gallons
NU Aqua 4-Stage RO System	1 gallon
Waterdrop N1	0.8 gallons

Wastewater Ratio

Yes, the RO process removes or reduces lots of contaminants, but not without producing wastewater. Some whole house RO systems can even send 5 cups of wastewater down the drain to produce just a cup of drinkable water.

Countertop water filter systems are considerably less wasteful than whole-house RO units because 1. their membranes are less effective, and 2. they don’t have a drain hose. Still, we’ve seen countertop systems that waste four cups to provide just one purified cup.

So, to be as eco-friendly as possible and to prevent high water bills, it’s best to opt for a system that has a low wastewater ratio.

Among the products we recommend, the system with the best wastewater ratio is the NU Aqua 4-stage Countertop RO System. It only wastes one cup of water to produce five healthy cups.

Countertop RO Systems	Wastewater Ratio (Pure water: Wastewater)
AquaTru RO System	1:1
RKIN U-1	1:1
NU Aqua 4-Stage RO System	5:1
Waterdrop N1	3:1

Maintenance Requirements

Semi-permeable RO membranes usually require replacement once every year, but it ultimately depends on the manufacturer's instructions and how frequently you use the system. Luckily, all the devices in this article have LED displays that’ll let you know when to replace the filters.

However, the RO membrane isn’t the only filter that needs replacing. Most of the devices we evaluated also feature carbon filters and pre-filters that you should replace once every 6 months.

In that sense, the RKIN U-1 is the most low-maintenance system on our list, as its RO filter needs replacing once every 24 months.

Countertop RO Systems	Filter(s) Replacement Frequency	RO Membrane Replacement Frequency
AquaTru RO System	4 to 6 months	6 months
RKIN U-1	6 to 12 months	24 months
NU Aqua 4-Stage RO System	6 months	6 months
Waterdrop N1	6 months	8 months

Warranty

It’s always a big plus when expensive devices that have electronic parts like LED displays have a good warranty.

However, we should note that most of these devices can only handle water conditions that are specified in the instruction manuals, and the manufacturer can void the warranty if you don’t comply with the specifications. So, carefully examine the instruction manual as well as the fine print on your warranty before use. All the products in this article have a one-year warranty.

Countertop RO Systems	Warranty
AquaTru RO System	1 year
RKIN U-1	1 year
NU Aqua 4-Stage RO System	1 year
Waterdrop N1	1 year

Price

RO systems are among the most expensive water treatment units on the market. Even though countertop RO systems are more affordable than whole-house ones, their price range is still higher than the non-RO systems: 0 – 0.

The most affordable option in our list is the Waterdrop N1 at 9, while the most expensive unit is the RKIN U-1 at 9.95.

Countertop RO Systems	Price
AquaTru RO System	1.65
RKIN U-1	9.95
NU Aqua 4-Stage RO System	5.95
Waterdrop N1	9

Important: Please note that the table shows prices as of March 2024, the time of writing this article, and that the prices are subject to change.

Frequently Asked Questions

Conclusion

To sum up, if you’re looking for an effective and reliable system, you should look no further than the AquaTru Countertop RO System. It’s NSF-certified, and its filtration capabilities are well-documented by independent test results.

The Waterdrop N1 is a sleekly designed unit that’ll look great on any countertop. Its 4-stage filtration is also nothing short of exemplary.

For those looking for a system compatible with hot water and well water, our recommendation is the NU Aqua System. It’s also the most eco-friendly option, with a wastewater ratio of 5:1.

We recommend the RKIN U-1 if you want a highly versatile unit that can provide hydrogen-enriched water.

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