The 10 Best Under-Sink Water Filters For Your Home: Reviewed and Compared

By: Jake Gallagher | October 23, 2023

If you’re going to get an under-sink water filter, you might as well get the best one.

But with all the diverse options and sales pitches out there, how do you know which one is the best? Whether you’re looking for a reverse osmosis (RO) system or a carbon-block system, some products deliver a better filtered water experience than others.

To make sure you can find the best under-sink water filtration system for your home, I’ve spent the past four weeks drinking, reviewing, comparing, and ranking the following filtration systems. Here’s what I found:

1. Waterdrop G3 Reverse Osmosis Water Filter System — 9.56/10 (Best under-sink filter)

The G3 RO Water Filter System is the best under-sink water filter for your home because of its high degree of water filtration, ability to handle a large capacity of water, compact size, and unbelievably easy setup. 

The best thing about the G3 system is that you get two different streams of purified water, satisfying all your water needs.


The G3 RO system has multiple certifications agreeing that it delivers the cleanest water produced by an under-sink filter. The Waterdrop tankless system has been certified and tested against NSF/ANSI standard 58 for 91.9% total dissolved solids (TDS) reduction and NSF/ANSI standard 372 for lead-free materials, which means that the G3 dispenses water purified from harmful contaminants like nitrate, arsenic, aluminum, and lead.

Waterdrop’s seven-stage filtration process eradicates chlorine, water scale, heavy metals, TDS, and other harmful impurities, restoring the quality and taste of your water. 

With a filter capacity of up to 11,000 gallons and a flow rate of 0.75 gpm, the G3 is perfect for larger households that consume a lot of water. There’s no waiting for the water to slowly pass through a carbon block or work through the filtration system itself.

With a physical size of only 18.06 x 5.68 x 17.76 inches, the G3 can fit into the tiniest areas. 

The G3 RO under-sink filtration system is one of the most manageable installations I’ve encountered. The single-stage filter installation took only 3 minutes, and the procedure took me 35 minutes in total. 

The one bad thing about water filtration is that it often removes essential minerals like calcium and potassium. This can affect your water’s taste, as well as your food’s flavor if you wash it in the same water.

But the G3 RO system’s two different filtered water sources eliminates this problem. A single-stage filter is attached directly to your water source and then sent to your regular faucet. This water filtration method keeps those essential minerals, making it perfect for cooking or washing vegetables. The system comes complete with its own faucet, which dispenses your filtered water.

This solves the need for two entirely different filter types and does it with efficiency, giving you water for every occasion.


The only con with the Waterdrop G3 is that when I ordered my unit (in the middle of the COVID disruptions), it took a few weeks to arrive. They claim to have this all fixed up and I’ve seen no mention of delivery delays in any of the recent reviews of their products and services, but it was an issue when I ordered.


The G3 RO Water Filter System is the best under-sink filtration system for your home because of its elevated water filtration process, capacity to regulate a large volume of water, consolidated size, and straightforward installation. 

While the COVID disruptions delayed my order delivery, its ability to deliver higher quality water is well worth the cost.

If you want an under-sink system for your home that delivers contaminant-free water in a compact size with an easy installation process, get Waterdrop’s G3 RO Water Filter System here.

2. Aquasana OptimH2O Reverse Osmosis + Claryum — 7.85/10 (Tasty, but with a slower pour)

The OptimH2O Reverse Osmosis + Claryum is number two because it delivers some mighty tasty water, but it also has a pretty slow pour while the water works its way through the filter system.


This Aquasana under-sink water filter combines RO technology and Claryum to clear 88 contaminants, including arsenic, chlorine, fluoride, lead, PFOA/PFOS, etc., resulting in super clean water. The system retains beneficial minerals such as calcium, magnesium, and potassium for more nourishing, delicious water.

The OptimH2O’s RO filters purify water without adding harmful chemicals to complete the process. It gives me peace of mind knowing that the water I’m drinking is entirely safe from contaminants.

Claryum Technology delivers four different methods of state-of-the-art filtration working in unison to extract 15x more impurities than the leading gravity pitcher filter.


The only thing to call out about the OptimH2O is that it has an awfully slow pour. It’s bearable at first, but your patience will thin over time. Compared to the G3, this pour feels like ages.

Strike two against this filter is that it makes a pretty loud gurgling sound when water is withdrawn from the filter. Not so bad if you just grab a glass of water, but if you’re pouring more water out than usual, the sound can last up to 45 minutes. 

Another point against this Aquasana filter is that although it says it’s an easy installation, it’s a bit more complicated than that. Having a friend who’s great at DIY will help quite a bit, but if you’re a loner like me, it’s a bit of a struggle. Filter replacements can be a struggle as well.


OptimH2O is my number two recommended under-sink water filter because it produces great-tasting water.

While they don’t deliver two different streams of filtered water or have as easy an installation, they’re a reliable second option.

If you’d like to know more about the OptimH2O by Aquasana, you can learn more about it on their website here.

3. ClearlyFiltered 3-Stage Under the Sink Water Filter System — 7.62/10 (Best for toxin reduction)

While the ClearlyFiltered 3-Stage Under the Sink Water Filter System produces only slightly above-average tasting water and the installation instructions are adequate, they’re still one of the best under-sink filters for toxin reduction.


ClearlyFiltered wants their water filtration unit to be known as a full-out toxin remover. Its heavy metal and volatile organic compound filter safeguard your drinking water from toxins like herbicides, pesticides, and heavy metals.

Installation was a relatively effortless process, and I tapped into the cold water line and hooked up the system in about 25 minutes. Yeah, it was that easy. 

The tanks for the unit are slimmer than most under-sink filtration systems, so they fit easily on the back wall of the cabinet, freeing up real estate on the bottom of the cabinet.


The first stage filter is meant to catch sediment and affect water taste, odor, and color—the only downside to the coconut filter block is that it works a little too well, zapping most of the water’s flavor away, unlike the G3 RO Water Filter System.

Although the installation was quick and easy, I have a background in under-sink water filters, and I’m pretty good with tools—if you’re not, you might have issues with the instructions, as they leave a lot to be desired. 

After installing the system, water pressure reduced dramatically, which meant I was waiting forever for my glass to fill. I could see my patience running thin pretty quickly.


The ClearlyFiltered 3-Stage Under the Sink System comes in third because while it produces average-tasting water and the installation instructions are adequate, it still offers drastic toxin reduction.

You will get far more filter life with Waterdrop’s G3. To learn more about ClearlyFiltered, do so here.

4. Home Master TMAFC Artesian Full Contact Reverse Osmosis System

The Home Master TMAFC Artesian Full Contact System claims the number four position because it produces great-tasting water with its mineral replacement feature.

This unit features a brisk fill-up, and customer service was extremely helpful when I had a question about the installation. I was also pleased with the water consumption rate and that it gave my tap water a rather good taste.

The actual system itself is pretty bulky and had a few more parts to it, which caused a bit of confusion when trying to put it together. Another downside was that the filtered water tap that comes with the unit is quite unsightly.

Overall, Waterdrop’s G3 RO System costs only a handful more and checks so much more off the water filtration checklist.

5. Brondell Circle Reverse Osmosis System

The Brondell Circle Reverse Osmosis System falls into the fifth spot because it has one heck of an elegant design and a significant impact on TDS.

This system has a feature designed to eliminate back pressure, conserve water, and provide even flow speeds, making it an efficient choice for under-sink water filters. Unfortunately, this unit’s efficient features reduce the water pressure in your home considerably. 

The cost of replacement filters isn’t super high, but with its recommended filter changes coming every six months, the price builds up substantially over time.

With the negatives against this unit, the G3 RO Water Filter System’s positives stand out even clearer, just like the water it filters.

6. AO Smith 2-Stage Water Filter

The AO Smith 2-Stage Water Filter instantly improves water flavor.

Its specialty faucet is one of the best I’ve seen and was a stunning edition to the countertop as well. It utilizes Claryum, which provides great-tasting and clear drinking water.

This unit didn’t place higher on my list because it’s pretty flimsy, and a couple of the seals broke on me. I picked up some replacement seals from Home Depot, and they did the trick, but it would’ve been better if I didn’t have to spend money on extra parts.

This unit also has an issue with an incorrectly sized O-Ring, so the filter sits a little out of joint, causing a bit of leaking. I picked up a correct-sized O-ring and replaced it—the unit was working well again.

Although the 2-Stage AO Smith system does a great job of improving water flavor, the fact that you have to buy extra pieces to make the system work is quite unfavorable. 

7. iSpring RCC7AK

The iSpring RCC7AK is in seventh place because it features one of the best chlorine removals of all the water filters I tested.

One big shout-out for this unit is that for some reason if you use the water it dispenses for coffee or tea, the result is quite tasty. I also noticed a positive change in my plants when I used the water to feed them. 

This unit, however, was pretty complex to understand and install, and the plastic housing seemed relatively cheap and easy to break.

Another strike against it was that the faucet it came with had a tacky finish (I would have preferred brushed nickel). I reached out to customer service only to find out that you can order a different one, but you have to pay an extra $10 to ship it. Not cool.

Although it does a great job of clearing up chlorine and can enhance the flavor of coffee, it can’t quite match up to the features of the Waterdrop G3.

8. iSpring CU-A4

The iSpring CU-A4 is another straightforward iSpring under-sink filter with quick installation.

This filter is one of the more accessible units to install and operate. The CU-A4 features a 0.01-micron ultra filtration (UF) stage that removes up to 99% of the most formidable contaminants, such as chlorine treatment by-products, arsenic, and lead, but retains healthy minerals.

The downside to this unit is that the manual is very confusing, and the installation process can be aggravating. I had to take time out and play with my dog to calm down. The taste of the water wasn’t that appealing, and I found myself not wanting to drink anymore of it.

With a less than desirable taste and a maddening installation, I have no problem recommending the Waterdrop G3 RO Water Filter System instead.

9. Hydroviv Under Sink Water Filter

Hydroviv Under Sink Water Filter is a space-friendly unit optimized for your local municipal water supply. The system uses your zip code to send you a filter built for the impurities in your local drinking water. If you think it sounds familiar, that’s because this under-sink filter was featured on an episode of Shark Tank.

This under-sink water filter only took 11 minutes to install, which was the fastest of all the installations I conducted. The filters also extract a whole range of contaminants related to many unwanted health issues, including chromium, arsenic, and lead.

Like anything unique, you will have to pay for it, and the Hydroviv is no different. Because it is curated for your local water situation, the unit’s cost and filter replacement prices are pretty high.

It also lags in filtering emerging contaminants, and it isn’t certified to filter them out accurately.

With the high price of maintenance and its lack of credibility, there’s a reason this isn’t my number one choice for under-sink water filters.

10. Express Water ROALK5D Reverse Osmosis Systems

The Express Water ROALK5D does a great job of adding minerals back into the tap water and raising the pH level.

This was one of the most manageable installations I’ve ever done, and it only took an hour for me to complete the process. The pressure rate is above average, and it didn’t take very long for me to fill my cup.

One of the reasons it isn’t placed higher on my list is because it emitted a very annoying squeal every time I fire up the filter system, and the water sometimes had a weird smell when it sat for a while in a cup.

Waterdrop’s G3, on the other hand, dispenses unbelievable water quality every time I pour it, and that’s why it is my number one choice for under-sink RO systems.

Bottom Line

After four weeks of intense under-sink water filtration researching, installations, and water tasting and testing, I proclaim the G3’s filtration systems as the number one choice for your under-sink water filter system.

This RO water filter provides two streams of highly purified water, the capacity to regulate a considerable amount of water, compact size, and unbelievably easy setup method. 

Although it has the highest price tag of all the filters I tested, you get what you pay for. This 10-stage system has the most transparent and tastiest water of the entire group.

If you want an under-sink water filter for your home that gives you the best filtration result possible, get the Waterdrop G3 RO Water Filter System now.


You’re probably asking yourself, how does he know so much about filter water? How about I tell you what went into creating this list?

Step 1: List of all the under-sink water filtration systems available

After moving into a new home, I realized that my new water supply tasted a lot like it was being pumped in from the dirty creek out back of the old Lucky Lager factory.

After a few weeks of trying to tolerate this fart water, I started investigating the water purification systems available to me. After looking at the available space, I decided that an under-sink filtration system would suit me better than faucet-mounted filters. 

For me, faucet filters were way too slow.

I spent a few days asking my friends what they were using to purify their water, searching the internet, and creating a list of 25 different under-sink filters.

Step 2: Online reviews

I realized that there was no way my wrists could type out 25 different reviews, so I concluded that 10 was a far better number. Far easier to type out.

I started to source online reviews for the water filters’ websites and found that some of them were more than likely made up. I love water filters, but geez, pouring it on a bit thick.

I weeded out the fake reviews and used my findings to eliminate ten more filters from my list. 

Step 3: Product/service analysis

Now that I was down to the final 15 filters, I got my hands dirty and started investigating and ordering the physical units. 

I had my water assistant, Baxter, order them, though. So my hands stayed pretty clean if I’m being honest.

While I waited for all the models to arrive at my home, I spent the rest of the day calling the companies to test out the customer service quality by asking questions:

  • What tap water filter systems will work in my home?
  • Why is a sediment filter important?
  • Out of all the filtration systems available, why is yours the best?
  • What‘s the difference between reverse osmosis filters and activated carbon filters?
  • What harmful contaminants does your filter capture?
  • Does your system have a whole-house system filter included in your kit?
  • How much will replacement filters cost?
  • Which filtration systems have the best filter capacity?

After watching Baxter spending a bunch of hours on the phone, I was able to whittle my list down to 12.

Step 4: Interviews with real customers

After completing my product analysis, I thought it might be a great idea to talk to other customers who’ve spent a significant amount of time using the under-sink filters I tested. 

Baxter and I began to research the two best and worst reviews we could find for each water filter and reached out to the customers who made them via email.

After messaging the customers about their under-sink filter system, I used their personal views of the product to influence my removal of the final two selections and arrive at my top ten candidates.

Step 5: Interviews with Aquasana, Waterdrop, and ClearlyFiltered

Now that I had my top ten selections, it was time to determine what the order would be. I reached out to the marketing teams for the ten under-sink filter systems and requested a quick five-minute interview for them to pitch their water filter systems to me and convince me why they were the best option available.

Out of the ten contacted, three returned my call. Burn.

Waterdrop, ClearlyFiltered, and Aqusana all returned my request for an interview, and we quickly chatted about the importance of carbon block filters, flow rate, filter replacement, and micro-sediment membranes. 

I was impressed with their knowledge level and customer service, which was a big reason why these companies claim the top three positions on this list.

Step 6: Test drives

Once all the water filters arrived at my home, it was time to take them for a test drive. I spent over four weeks assembling every filter housing, installing every separate faucet, adjusting water flow, and bashing my head on the kitchen sink to figure out the ranking of my top ten. 

It was time to rate these filters and crown one of them as the top water filtration system out of all the under-sink options.

Step 7: Ratings

When it came to the rating of the top ten water filter systems, there were some significant factors to consider:

  • Was it a trusted under-sink filtration system?
  • What makes under-sink filters a better choice than countertop filters?
  • How easy was it to install using only the cold water feed line? How easy is the filter replacement process?
  • Do any of the options include a whole-house filter as well?
  • How much is a reverse osmosis filter compared to an activated carbon one?
  • Do these systems come with a separate faucet? What will it take to have the separate faucet installed?
  • Will these filters affect the temperature of my cold water supply?

Best Under-Sink Water Filter for Purifying Your Water

After four weeks of intense filter experimentation, the Waterdrop G3 RO Water Filter System was the number one under-sink filter.

It is the best under-sink water filter for your home because of its high degree of water filtration, ability to handle a large capacity of water, compact size, and unbelievably effortless installation.

Cold water on command, high-pressure flow, and an all-around pure water drinking experience make this filter my number one choice.

  • Cold water valve ready for easy access
  • Dedicated water faucet for use
  • High purification rates for a bettbester-tasting water
  • Straightforward setup for immediate use
  • Two distinct streams of filtered water

While the cost is on the pricey side, the features and benefits of the G3 filter far outweigh the hit to the wallet.

If you want an under-sink water filter for your home that will set up easy, purify water immediately, and deliver delicious H20, get the Waterdrop G3 RO Water Filter System now.

If you’re eager to expand your knowledge about different water filters, we provide a wide range of articles that explore various options and their functionalities. Here are a few articles you can explore:

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