Best Under-Sink RO Systems • (2024 Reviews)

Last Updated Feb 16, 2024
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Investing in an under-sink reverse osmosis water filtration system is an excellent choice for countless reasons. One of the main reasons is the cost savings compared to buying bottled water. Considering that most bottled water is RO water with added minerals, why not make your own at home? In this article, I share my Top 5 picks for the best reverse osmosis under sink system.

The systems in this guide are great for purifying both municipal and well water. As you move through the guide and Top 5 chart, you’ll quickly land on the perfect filter for your home or apartment. You might find that a 5-stage system is all you need to get the job done, while people on well water may want to opt for additional stages. Depending on your current setup, an under-sink RO unit is almost always compatible.

People on well water with existing water softeners can easily upgrade their drinking water quality with an RO filter. Keep in mind, RO systems and water softeners serve different purposes, though when combined, transforming well water into bottled-water quality h2O is highly possible. Let’s start below with a Top 5 chart before moving on to the reviews for each of the five models.

#1) Home Master HydroPerfection

  • #1 Best-Rated Under Sink Reverse Osmosis System
  • Stages: 9
  • Capacity: 75 GPD
  • Model: TMHP
  • Dimensions: 15″ x 5″ x 16″ (L x W x H)
  • Weight: 18.75 lbs
  • Warranty: 5-Year Limited
  • Price: $$$
#2) APEC Water Systems Ultimate RO-Hi

  • #1 for Large Families
  • Stages: 5
  • Capacity: 90 GPD
  • Model: RO-HI
  • Dimensions: 16″ x 5.2″ x 17.5″ (L x W x H)
  • Weight: 26.9 lbs
  • Warranty: 2-Year
  • Price: $$
#3) iSpring 7-Stage Reverse Osmosis

  • #1 for Well Water
  • Stages: 7
  • Capacity: 100 GPD
  • Model: RCC1UP-AK
  • Dimensions: 15.3″ x 9.1″ x 18.1″ (L x W x H)
  • Weight: 35.3 lbs
  • Warranty: 1-Year
  • Price: $$$
#4) APEC Top-Tier Reverse Osmosis
  • #1 w/ Alkaline Remineralization
  • Stages: 6
  • Capacity: 75 GPD
  • Model: ESSENCE ROES-PH75
  • Dimensions: 16″ x 5.2″ x 17.5″ (L x W x H)
  • Weight: 27 lbs
  • Warranty: 2-Year
  • Price: $
#5) Express Water Alkaline Ultraviolet RO Water Filtration System

  • Top-Rated Budget Under-Sink RO System
  • Stages: 11
  • Capacity: 100 GPD
  • Model: ROALKUV10M
  • Dimensions: 14″ x 5″ x 15″ (L x W x H)
  • Weight: 30.2 lbs
  • Warranty: 1-Year
  • Price: $

Reverse Osmosis Under Sink Water Filter Reviews

As you probably already noticed, there are several types of RO systems in the chart above. What makes one system better for well water than another? One key component to seek for well water applications is a UV sterilization filter. Unless you treat your well water with chlorine or another disinfectant, there’s a chance of microorganisms creeping into your private well. This usually occurs after rainfall or snowmelt. UV sterilization is a superb chemical-free method for zapping harmful microorganisms including bacteria.

If you have hard well water, it’s best to install a whole-house sediment filter and water softener at the point of entry before the water reaches the RO unit beneath your sink. This combination is a complete home water filtration system, and it ensures that you get the most life out of your filters and the most delicious drinking water on tap.

For those of you on municipal water, there’s really no need for a UV filter since your water utility uses chlorine or chloramines to disinfect your water supply. This also adds a second factor to the equation. That’s why it’s important to call your local water utility to determine whether there are chloramines or chlorine in your tap water. Although an RO membrane removes everything from your water, a catalytic carbon pre-filter is a good choice for chloramine removal before the water reaches the RO membrane.

Now that you’ve considered the most important points, let’s move on to the individual reviews of each system. Be sure to check out the pros & cons to find out what to expect from each system before you buy one.

Home Master HydroPerfection (TMHP)

I know, I know, this system isn’t the prettiest one to look at, but oh boy, it delivers. The name “HydroPerfection” is perfect for this system because that’s exactly what it does, makes perfect drinking water. The TMHP is one of the few models on the market that makes true artesian-quality drinking water. There’s a good chance you won’t be able to tell the difference between the water from this unit and expensive bottled water brands like Fiji. That’s how good it is.

How does the system achieve this feat? The key lies in the patented “Full Contact” technology that adds alkaline minerals calcium and magnesium twice during the filtration process. This unique process does a better job of improving taste than standard mineral filter cartridges found in most systems. On top of that, the system features a UV filter, making it great for well water out of the box. Even people on municipal water may like the extra peace of mind of having a UV filter.

In addition to those components, there are two additional elements that I like a lot in a system. The first one is a permeate pump that increases the flow rate at the faucet and the overall efficiency of the system. This equals less wastewater created during the filtration process. The second element is the powerful catalytic carbon pre-filter for enhanced chloramine removal. Additionally, this system features KDF85 redox media for enhanced iron removal. This element is great for people on well water with a hydrogen sulfide problem (rotten egg odor).

All in all, this is the best all-in-one system on the market for both well and municipal water. The one drawback is people on municipal water may find that the UV filter and additional filter media in the pre-filters are unnecessary since the water gets pre-treated. For people on well water, the only system on par with this one is the iSpring RCC1UP-AK. Last but not least, the 5-year warranty is the longest you’ll find offered by the top RO brands.

  • Simply amazing-tasting water
  • Coffee drinkers love this RO water
  • Clear ice cubes
  • It pairs perfectly with exisiting water softeners
  • Annual filter changes (most systems require more frequent filter changes)
  • Excellent customer service
  • Very clear installation instructions (no broken English)
  • You may find that the taste is similar to Fiji water or other bottled artesian water brands
  • Ample flow rate, fill pots quickly
  • You might not like the cluster of mounting brackets compared to the more traditional system design
  • A handful of leak reports
  • Not easy to install for everyone

APEC Water Systems Ultimate RO-Hi

For people on city water who want a system that’s built to last for decades, this is the one. It’s also ideal for large families and other high-demand applications because of its fast flow rate. One thing I like about both Home Master and APEC is the sheer quality of both companies’ RO membranes. They both offer the highest max recommended incoming TDS of 2000ppm. For people with high TDS water, APEC and Home Master are the #1 choices.

The filters in this system are made in the US, plus, APEC systems are designed, engineered, and assembled in the US. This California-based company is one of my personal favorite RO brands if you haven’t noticed already. What makes the Ultimate RO-Hi special? The key ingredient is the 3/8″ fast-flow design that’s great for filling pots and serving large households. Compared to the Home Master HydroPerfection system, the RO-Hi costs a good bit less.

The fact that this system is WQA Gold Seal certified is another major selling point. I also like that this system is low-maintenance. Fewer stages equal fewer filters to monitor and maintain. Like Home Master, APEC filters last for up to a year, which means no crawling under your sink every few months. The final point to consider is the higher max production rate of 90 GPD compared to the 75 GPD rating offered by the Home Master filter.

  • The filter housing is diesel, built to last for decades
  • APEC customer service is top-notch
  • Fills pots more quickly than standard systems
  • Consistently low PPM readings
  • Well-written instructions that ensure a proper installation
  • An excellent choice for large families and people who drink a lot of water daily
  • Delicious RO water
  • Clear ice confirmed
  • More wastewater than a system with a permeate pump
  • No UV filter for people on well water

iSpring 7-Stage Reverse Osmosis (RCC1UP-AK)

The three companies I trust the most in the RO department are Home Master, APEC, and iSpring. iSpring is a family-owned water filtration company based in Georgia that cares about the customer and the quality of its products. With iSpring, you get not only an excellent system but awesome customer support as well.

The RCC1UP-AK is very similar to the HydroPerfection TMHP model, as both systems feature UV filtration, alkaline remineralization, and a permeate booster pump. For people on well water, the RCC1UP-AK and TMHP are the best-rated under-sink RO systems on the market. The one drawback to this unit compared to the Home Master is the lack of the patented “Full Contact” technology. You may find that the TMHP makes water that’s more comparable to real artesian water than the iSpring system.

One feature I like a lot is the combination of KDF-Carbon and carbon block pre-filters that effectively remove both chlorine and chloramines during the pre-filtration stages. The final granular activated carbon (GAC) filter does the final “polishing” after the water exits the RO membrane for superior-tasting water. This combination of filters makes true bottled-water quality water to please even the pickiest water snobs.

  • The transparent sediment filter housing makes monitoring filter life quite easy (I like this more than opaque housing)
  • Effectively transforms well water into delicious drinking water, you might not be able to tell you’re drinking well water
  • Smooth installation process
  • Awesome customer service from a family-owned company
  • Crystal-clear ice cubes
  • Comparable to expensive mineral water
  • The filter housing isn’t on par with the APEC RO-Hi
  • Installation might feel complicated
  • Too big for some kitchens (be sure to measure before you buy)
  • Several reported problems with the UV light

APEC Top-Tier Reverse Osmosis (ROES-PH75)

Compared to the three systems above, the ROES-PH75 costs significantly less. This is my favorite RO system w/ remineralization for the price. What I like about APEC remineralization cartridges is I know they’re made in the US with high-purity, US food-grade calcium carbonate. When it comes to remineralizing my RO water, I don’t want to mess around with any minerals imported from China. There’s absolutely no reason for a company to do that other than to cut costs.

In addition to the high-grade calcium carbonate, this system features mostly all of the same quality APEC components as the RO-Hi unit for a more affordable price. All APEC systems include food-grade JG tubing, lead-free auxiliary faucets, and leak-free quick-connect fittings to make installation easy-peasy. Plus, you get the comfort of a 2-year warranty on parts from a trustworthy company.

  • The easiest installation of the systems in this guide, approved by seniors
  • Extremely quick responses from customer service and almost no hold time on calls
  • APEC water is known for its signature delicious taste (this is where the importance of the US food-grade calcium comes into play)
  • You might not notice a difference between the RO water from this unit and store-bought alkaline water
  • Remineralization livens up the flat taste of plain RO water
  • Low ppm readings
  • More wastewater than systems with booster pumps
  • No UV purification
  • A couple of missing part reports

Express Water Alkaline Ultraviolet RO System (ROALKUV10M)

The final system is the best-rated budget RO under-sink filter available. The ROALKUV10M is essentially the same type of system as the Home Master HydroPerfection and iSpring RCC1UP-AK for about half the price. The only missing element compared to those two systems is no permeate pump included, though, it is possible to upgrade later. When you factor in the cost of a permeate pump, this system still costs a lot less than the iSpring and Home Master filters.

One thing that’s somewhat deceiving about this unit is the “11-stage” label. In reality, this is a 7-stage system with remineralization and UV filtration stages in addition to the typical 5 stages. Express counts its remineralization stage as 5 stages because the mineral filter cartridge adds a more diverse set of minerals.

The main difference between Express remineralization and APEC is the addition of magnesium and potassium in the Express cartridge. You may find that you prefer the taste of Express remineralized water over APEC since APEC uses calcium carbonate only.

The final highlight is Express Water’s customer service. Of all the top budget RO brands, I trust Express Water the most.

  • A smooth and fresh-tasting water that’s better than bottled water
  • Clearer ice cubes
  • Easy installation and excellent customer service should you have any questions along the way
  • Crystal-clear drinking water after installation
  • Unbeatable value for the money
  • A perfect solution for foul-tasting well water
  • More wastewater than iSpring and Home Master filters
  • You might not like the flavor
  • A couple of quality control issues

Bottom Line

Now that you’ve learned how to select the best reverse osmosis under-sink system and checked out the top filters available, I’m sure you’ve already selected a system. As a reminder, consider your water source before selecting one. While the Home Master TMHP is awesome for all water types, you may find that it’s more than you need to purify your city or town’s water. People who need to purify untreated well water will get more value from it since it includes a UV sterilization stage.

Another component to consider is a permeate pump, and these are great for everyone. With a permeate or “booster” pump, you make a lot less wastewater and get more pressure at the faucet. Of the systems in this guide, the Express Water and APEC units are the most affordable at the time of this writing.

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