AquaOx Reverse Osmosis Under Counter Water Filter

Overview: AquaOx Reverse Osmosis Water Filter

The AquaOx RO Kitchen Sink Filter uses a four-stage reverse-osmosis filtration system to effectively remove the vast majority of unwanted substances from your tap water. It is easily installed under the kitchen sink so that you can enjoy 24/7 access to high-quality drinking water direct from your faucet. The unit’s proprietary quick-change manifold makes maintenance easy. Overall, this product gives you consistently high-quality drinking water direct from your tap. All this comes for a fraction of the price of bottled alternatives.


The AquaOx RO System delivers an impressive lineup of features. For one, it is capable of removing most unwanted substances that are bigger than 0.0001 inch. This includes:

  • Carcinogens
  • Heavy metals
  • Chlorine
  • Cryptosporidium
  • Salts
  • Turbidity
  • Nitrate
  • VOCs
  • Organic Compounds
  • Dissolved Solids
  • Tastes and Odors
It has also been proven to remove approximately 96% of ions from water.

The AquaOx Twist-Loc Reverse Osmosis is capable of producing up to 30.65 gallons of purified water per day.

The included storage tank can hold up to 3.2 gallons of H20 reserves.

Over a year, you’ll spend a fraction of what you would if you were to have purchased bottled water.
AquaOx Reverse Osmosis Water Filter


The AquaOx RO system offers high-quality drinking water direct from the tap. This enables you to avoid unsustainable and expensive bottled alternatives while still reaping the health benefits of top-level water purification.

What we love about this model is that it comes with a separate faucet. This means that your purified drinking water flows independently and, therefore, has no impact on your regular cold and hot water.

Also, here are a few more benefits of the system:

Effectively Eliminates Impurities

The AquaOx Reverse Osmosis (RO) Kitchen Sink Filter has been proven to eliminate 96% of ions from potable tap water. This includes hard-to-remove contaminants, such as chromium-6, fluoride, and arsenic. Total dissolved solids, radionuclides, uranium, sulfates, nitrates, and nitrites also make the list of pollutants that are stopped by the system’s filter quad.

Stage one of water filtration consists of a 5-micron sediment reducing filter. This filter boasts a 0.5 gallon per minute flow rate and a 6-month lifespan. It is proven to remove contaminants like sediment, rust, dirt, and debris.

Following this is a carbon filter that is capable of removing excess chlorine, bad tastes, and unpleasant odors. This filter is also rated to last 6 months.

This is followed by a reverse osmosis membrane. It has a 35.33% recovery rate, a 23.16% efficiency rating, and a 98% total dissolved solids (TDS) reduction rate. It is rated for 24 months. The reverse osmosis filter consists of a composite membrane. The membrane traps things like metals, salts, and contaminants before flushing them down your wastewater drain.

Stage four is a second carbon filter that is identical to that of stage two. As water passes through this last filtration stage, any remaining odor and tastes will be eliminated.

Unfortunately, the AquaOx does not boast a remineralization filter. As such, you will be missing out on the benefits of re-add calcium and magnesium.

Easy Installation

The entire AquaOx installation process takes no more than an hour to complete. All of the necessary elements, save for a few common household tools, are included in the package. The process is relatively easy and does not require any advanced plumbing procedures or specialty tools. However, the company does advise individuals to explore their local plumbing code requirements before commencing installation.

The reverse osmosis filtration system needs to be mounted to a rigid vertical surface, such as a cabinet wall, sheetrock, or an exposed stud. It must also be set up so that you can easily run tubing from the manifold to a nearby cold water source and a wastewater drain. Finding an appropriate mounting location under a sink shouldn’t be much trouble. Keep in mind that you will want to be able to easily access the front of the manifold so that you can perform filter changes.

The AquaOx RO Kitchen Sink Filter also boasts Nelsen’s Quick Change, Twist & Loc filter system. This proprietary system enables users to remove and replace all four filters without ever turning off the water.

The provided tubing is easy to cut and install. All that’s needed is a sharp knife, silicone lubricant, O-rings, and push-to-connect tubing connectors.

You will also need to install the included faucet. The complexity of this step is dependent on the material consistency of your mounting surface. If you are mounting the faucet to a stainless steel sink lip, you can simply drill a hole in the material using a ⅞-inch drill bit. 

You may also use your sink’s spray faucet hole if it is available. Users should also find it easy to install the faucet atop porcelain enamel sinks. Keep in mind that special tools, including a spring-loaded porcelain saw and finish hole saw, are required. When it comes to installing the faucet on more delicate surfaces, AquaOx recommends that customers seek professional assistance. 

With all that said, it’s worth noting that AquaOx goes above and beyond to provide users with full-color, illustrated guides for installation and maintenance. Not to mention, you can always reach out to the company via chat or phone. 

What’s Included?

The AquaOx kit comes with all the essentials. Including four clearly marked filters, a filter manifold, a tank ball valve, a 3.2-gallon storage tank, a faucet, and installation hardware.

Price Considerations

The AquaOx RO retails for $489. If you cannot afford to pay for the entire thing upfront, you can finance your purchase through Affirm. This third-party financing company offers three, six, and 12-month payment plans for those that qualify. This means you can pay as little as $44.19 per month for one year. You can also use PayPal Credit to receive no interest on any charge over $99 that is paid in full in 6 months.

Replacement Filters

The AquaOx RO Filtration System utilizes Nelsen Twist & Loc filters. Unfortunately, the company does not sell replacements. With that said, you should have no trouble finding affordable replacements.

You will need two Twist-Sediment (Stage 1), four Twist-Carbon (Stages 2 and 4), and one Twist-Membrane (Stage 3) to get you through a year. The Twist-Membrane filter is the priciest of the bunch. It carries an MSRP of $70. The Twist-Carbon filters are valued at $17.50, and the Twist-Sediment cost $15.60 apiece. You can learn more about Nelsen filters here.

It’s worth noting that the Twist-Sediment and Twist-Carbon filters are rated for 6 months. Meanwhile, the Twist-Membrane filter is rated for 24 months.

Pros & Cons


AquaOx is a veteran-owned American business. The owner is Michael Corcoran, a retired US Army Lieutenant Colonel. He’s made it his mission to provide homeowners with affordable, reliable, and easy-to-use water filtration systems.

The under-the-sink filtration kit comes with everything you need to complete your installation. Although, you may need an electric drill and stepped 7/8 -inch drill bit if you intend to mount the faucet to a countertop or stainless steel sink lip.

The AquaOx’s installation guide and product specs can be viewed online.

All AquaOx products are covered by a limited one-year warranty and a 10-year elite warranty. Moreover, the company offers 24/7 online customer service.

AquaOx offers zero-down financing through a third-party company. You can find the information on the AquaOx RO product page.

The AquaOx reduces contaminants, bad smells, and unpleasant tastes. Therefore, it is ideal for those that are concerned about the quality and enjoyability of their water.

Since the filtration system comes with a faucet, it does not interrupt the flow of your regular cold and hot water.

Contaminants are washed away from the cartridges to promote the longevity and reliability of the filters.


Users must consider several factors before they can determine if the AquaOx system is a good pairing for their home water system. These factors include water pressure, total dissolved solids levels, water temperature, and water pH.

Since the AquaOx system uses Nelson Twist & Loc Filters, you’ll need to navigate beyond the company’s webpage to purchase your annual replacements.

While it doesn’t take long to fill a water bottle or jug with the AquaOx, water pressure is noticeably decreased by the inline filters.

Finally, at this point in time, AquaOx hasn't added a remineralization stage to this latest offering.

This is probably the largest issue we have, because in order to re-introduce healthy minerals to the water at this point you would need to add a few drops of supplemental minerals (like these Anderson's Sea M.D. Concentrated Trace Mineral Drops, which we use when we are intending to drink RO water - we add about a dropper - a dropper and a half to a gallon).

How does the AquaOx RO System stand up to the competition?

AquaOx vs Home Master TMULTRA-ERP RO System

It’s easy to see why one would compare the AquaOx RO to the Home Master TMULTRA-ERP RO. Both models feature four filters that include reverse osmosis media, and both models boast a 3.2-gallon tank. Moreover, both of the units are designed to be installed under a sink and require minimal installation. Moreover, both models promise to remove a lofty level of contaminants.

When it comes to price, both the Home Master and the AquaOx retail for just under $500. Since the Home Master is available through third-party retailers, you’re more likely to find it marked down. Still, there are obvious benefits to buying directly from the manufacturer. It’s worth noting that AquaOx receives rave reviews regarding its accessibility and customer service. There is even a live chat option and answers to FAQs at the bottom of the AquaOx page.

While Home Master touts the benefits of their added ultraviolet light filter, we felt that the additional electric connection requirement was a bit of a nuisance.

With a 1-to-1 waste to recovery rate, the Home Master takes the win for efficiency. Still, with a 1-to-3 water recovery rate, the AquaOx isn’t falling far behind. Meanwhile, with all four of the AquaOx’s filters rated for 2,500 or more gallons, it reigns in terms of lifespan.

AquaOx vs iSpring RCC7AK-UV 7-Stage Reverse Osmosis System

The iSpring RCC7AK-UV 7-Stage Reverse Osmosis System is also a close alternative to the AquaOx. With a single kit costing no more than $150, it’s an obvious choice for the most budget-savvy consumers. Its filtration and efficiency stats are right up there with that of the AquaOx and Home Master. It boasts seven filtration stages, including ones that add back minerals and provide UV sterilization. However, it has also received some negative feedback regarding leaks.

AquaOx vs Brondell H2O+ Circle Reverse Osmosis Water Filter

The AquaOx can also be compared to the Brondell H2O+ Circle Reverse Osmosis Water Filter. This compact unit contains a 6-liter water reservoir and an onboard filtration system. Its hallmarks include a simple installation, compact design, and energy efficiency. With that said, it does not come close to the AquaOx in terms of water pressure, daily gallon production, or ease of maintenance. So, once again, the AquaOx manages to reign supreme.

Our Recommendation

It is clear to see that the AquaOx Reverse Osmosis Kit is one of the premier under-the-sink water filtration systems on the market. This four-filter manifold manages to eliminate even the most stubborn contaminants, odors, and tastes. Thus, you get seriously clean water straight from your tap.

The entire thing costs a fraction of the cost of bottled water. It ensures that you and your family have 24/7 access to the highest quality water.

Of course, if you’re looking for a simpler, less expensive, or more compact option for an RV, tiny house, boat, or another unconventional setup, be sure to check out the AquaOX DF 1. This compact point-of-use filtration system must also be installed under a sink. The single-stage coconut shell carbon and quantum disinfection media are capable of removing a wide range of harmful contaminants, including chlorine, pesticides, pharmaceuticals, bacteria, pathogens, and more. It retails for $299 and is suitable for up to 15,000 gallons of use.

You might also be interested in AquaOx’s whole-house filter. This system boasts seven stages of filtration. Depending on the model, it can produce enough water for anything from a one- to a four-bathroom household. Check out our review of AquaOx and other top-rated whole-house filters here and here. Keep in mind that at $3,499 to $4,9999, this filtration system is a major investment.

With that said, the AquaOx RO Under-the-Sink Kit is the ideal pick for anyone looking to improve the health and quality of subpar tap or well water while circumventing wasteful and expensive bottled alternatives. With a production rating of over 33 gallons of water per day, the unit is perfectly suitable for a large family. While the upfront cost is a bit steep, the savings are sure to add up over a year or two. 
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