Written by: Alexandra Uta // Last Updated:
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There are so many advantages to high quality under sink water filters. For one, they are effective at removing a wide range of potentially harmful contaminants. Secondly, they are affordable, easy to install and maintain – filters usually last a long time – and convenient to use. Basically, you get clean and great tasting water straight from the tap whenever you need it.
Above that, under sink filters don’t take up any space on your kitchen counter (who would have guessed) and most only little space underneath it, which is great if you have a small kitchen.
The only problem: With so many products out there, how do you find the best under sink water filter for your home? After all, you don’t want to waste your money on a substandard product… Well, you came to the right place!
On This Page You Will…
Model | Details | |
---|---|---|
![]() Best Under Sink Water Filter with Most Contaminants Removed: Clearly Filtered 3-Stage | Get 15% Off! Use Code: |
Price: $$$ Type: 3-Stage Under Sink Water Filter, Inline Filter Life: 2,000 gal Testing & Certs: NSF 42, 53, 401 Warranty: Lifetime Read Review: Click Alexa’s Video Review: Click |
![]() Best Under Sink System with Reverse Osmosis: Aquasana OptimH2O | Get Up to 50% Off! Use Code: |
Price: $$ Type: RO System Filter Life: 6-12 mos Testing & Certs: NSF 42, 53, 58, 401, P473 Warranty: 2 Years Read Review: Click |
![]() Best for Tankless Under Sink RO Purification: Waterdrop WD-G3-W | Get $50 Off! Use Code: |
Price: $$$ Type: RO System Filter Life: 550-2,200 gal Testing & Certs: NSF 58 Warranty: 1 Year Read Review: Click Alexa’s Video Review: Click |
![]() Best Budget Option: Epic Smart Shield | Get 20% Off! Use Code: |
Price: $ Type: Single-Stage, Inline Filter Life: 650 gal Testing & Certs: NSF 42, 53, 401 Warranty: Lifetime Read Review: Click Alexa’s Video Review: Click |
Review Order
In our opinion, the best under sink water filter in 2023 is the Clearly Filtered 3-Stage. It has been repeatedly tested to remove/reduce well over 200 different water contaminants which is simply outstanding, especially for an under sink water filtration system that doesn’t apply reverse osmosis (RO).
Installation and maintenance are a piece of cake, and users are highly satisfied with their purchase. 5 stars!
![]() Clearly Filtered 3-Stage Under Sink Water Filtration System | |
Price: | $$$ |
Filter Type: | 3 Stages, Inline |
Filtration Capacity: | 2,000 gal |
Testing: | NSF 42, 53, 401 |
Annually: | $400 |
Our Rating
Get 15% Off! Use Code: |
Pros
Cons
Best for
The Clearly Filtered 3-Stage system is best for people who want an under sink drinking water filter that’s compact, easy to connect and use, and highly effective.
In our opinion, the number one under sink reverse osmosis system in 2023 is the OptimH2O by Aquasana. Why? Because it’s highly effective at reducing dozens of harmful contaminants from water and, at the same time, it remineralizes the filtered water with healthy calcium, magnesium, and potassium. This improves the taste of the water and balances its pH. All in all, an excellent offer. 4.5 stars!
![]() Aquasana OptimH2O Reverse Osmosis Water Filtration System | |
Price: | $$ |
Filter Type: | RO System, Dedicated Faucet |
Filtration Capacity: | 6-12 Months |
Certifications: | NSF 42, 53, 58, 401, P473 |
Annually: | ~$180-220 |
Our Rating
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Pros
Cons
Best for
The Aquasana OptimH2O is best for people looking for an under sink reverse osmosis system that’s easy to install and maintain, NSF-certified for contaminant removal, and that provides slightly alkaline drinking water.
If you lack the necessary space under your kitchen sink, we have the ideal solution for you: The Waterdrop WD-G3-W tankless under sink reverse osmosis system. Because the system filters on demand it doesn’t need a water storage tank which saves a fair bit of space in your sink cabinet.
Plus, it makes the installation even simpler. This in addition to great drinking water taste are worth four stars from us.
![]() Waterdrop Tankless Under Sink RO System | |
Price: | $$$ |
Filter Type: | RO System, Own Faucet |
Filtration Capacity: | 550-2,200 gal |
Certifications: | NSF 58 |
Annually: | ~$115 |
Our Rating
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Pros
Cons
Best for
The Waterdrop WD-G3-W is best for people who want a tankless under sink RO system that’s small, easy to use, and fast.
The Epic Smart Shield is a non-RO (reverse osmosis) under sink filter system perfect for tap water and well water. It’s certified to remove contaminants including lead, chlorine/chloramine, asbestos, cyst, E. Coli, and many other. Furthermore, it’s surprisingly affordable especially when compared to the Clearly Filtered 3-Stage under sink water system reviewed above and users love the great taste of the purified water. 4.5 stars!
![]() Epic Smart Shield Undersink Water Filter | |
Price: | $ |
Filter: | One Stage, Inline |
Filtration Capacity: | 650 gal |
Certifications: | NSF 42, 53, 401 |
Annually: | $110 |
Our Rating
Get 20% Off! Use Code: |
Pros
Cons
Best for
The Epic Smart Shield is by far the best budget under sink water filter.
Crystal Quest’s 1000C and 1000CP are great RO under sink filters for people on well water.
Side note: The only difference between the two is the latter comes with an electronic pump to boost water pressure.
With 12 filtration stages, both systems are capable of eliminating all contaminants commonly found in wells and many more.
And if you want you can add a 13th filter stage (UV light) on top for 99.99% reduction of microorganisms – think bacteria, viruses, and protozoa. This turns the Crystal Quest 1000C into the 3000C, and the 1000CP into the 3000CP.
![]() Crystal Quest 1000C | |
Price: | $$ |
Filter Type: | RO System, Separate Faucet |
Filtering Capacity: | Varies |
Certifications: | – |
Annually: | ~$100-155 |
Our Rating
Get 5% Off! Use Code: |
Pros
Cons
Best for
These under sink water filters by Crystal Quest are best for heavily contaminated well water.
Aquasana sells not one, not two, but three regular under sink filters: The AQ-5200, AQ-5300, and the AQ-5300+ a.k.a. 5300 Max Flow. They all combine activated with catalytic carbon filter media to effectively remove or reduce a wide range of common tap water contaminants.
Why 3 under sink filters then? That’s because the Aquasana AQ-5200 is a 2-stage system. AQ-5300 and 5300+ use a third filter stage: A sediment pre-filter. Filtering sand, dirt, and rust etc. it protects the other filters from clogging, extending their lifespans.
And filters of the AQ-5300+ last even longer than those used by the AQ-5300 due to their larger size. By the way, larger filters also mean higher flow rates.
All in all, we rate both AQ-5200/5300 with 3.5 stars and the AQ-5300+ with 4!
![]() Aquasana AQ-5300+ Under Sink Water Filtration System | |
Price: | $ |
Filter Type: | 3 Stages, Extra Faucet |
Filtration Capacity: | 800 gal |
Certifications: | NSF 42, 53, 401, P473 |
Annually: | $160 |
Our Rating
Get Up to 50% Off! Use Code: |
Pros
Cons
Best for
These Aquasana under sink filters are best for NSF-certified contaminant reduction achieved through multi-stage filtration (non-RO).
Just like Aquasana, Culligan provides three under sink water filtration systems with one interchangeable filter each: The US-EZ-1 (or Easy-Change 1), the US-EZ-3, and the US-EZ-4. The reason why we decided to review them is they’re a low-cost alternative to all the filters listed above and therefore perfect for people on a tight budget.
Where’s the difference between US-EZ-1, 3, and 4? In a nutshell, the US-EZ-1 provides basic chlorine filtration only. The US-EZ-3 is more advanced. And the US-EZ-4 is certainly the most sophisticated under sink water filter system providing premium filtration.
All things considered, we wouldn’t recommend the US-EZ-1 unless you already have really good water and are only concerned about taste issues. Thus 3 stars. The US-EZ-3 is okay, we’ll award 3.5 stars. But we would only really recommend the US-EZ-4 to most of our readers. 4 stars!
![]() Culligan US-EZ-4 | |
Price: | $ |
Filter: | One Stage, Extra Faucet |
Filtration Capacity: | 500 gal |
Certifications: | NSF 42 + 53 + 401 |
Annually: | ~$120 |
Our Rating
|
Pros
Cons
Best for
Culligan’s under sink filtration systems are best for customization. You can switch between the different cartridges.
Next on our list: The CuZn UC-200 inline water filter.
Water is supposed to be almost tasteless. If that’s what you are looking for and your water doesn’t contain certain contaminants that the CuZn under sink filter can’t handle, definitely give it a shot. You can’t really go wrong. Remember: If you don’t like what you receive, claim the guarantee.
CuZn UC-200 Under Counter Water Filter | |
Price: | $ |
Filter: | Single Stage, Inline |
Filtration Capacity: | 50,000 Gallons |
Testing: | NSF 42 |
Annually: | – |
Our Rating
|
Pros
Cons
Best for
Due to 50,000 gallons filter life, the CuZn UC-200 is best if you want a maintenance-free under sink filter system.
You want unlimited access to refreshing drinking water at home? Both Woder 10Ks can give you that. The filters are affordable and backed by hundreds of positive customer ratings. Did we mention Woder’s “YOU’LL LOVE IT”-guarantee? Either you love what you get or you send it back and receive a full refund. What are you waiting for? Go check it out!
Woder 10K-DC Inline Water Filtration System | |
Price: | $ |
Filter: | One Stage, Inline |
Filtration Capacity: | 10,000 gal |
Testing: | NSF 42 |
Annually: | – |
Our Rating
|
Pros
Cons
Best for
The Woder 10K is best for basic water filtration certified through NSF standard 42.
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Filter Systems | Price | Type | Capacity | NSF | Annually | Additional Info |
---|---|---|---|---|---|---|
Clearly Filtered 3-Stage System | $$$ | Inline | 2,000 gal | 42, 53, 401 | $400 | Designed to Remove 200+ Municipal Water Contaminants (Beneficial Minerals Are Preserved), Stainless Steel Hoses, Simple Filter Change |
Aquasana OptimH2O Undersink Filter | $$ | RO | 6-12 Months | 42, 53, 58, 401, P473 | ~$180-220 | Achieves Bottled Water Quality, Adds Healthy Minerals, 3 Faucet Designs Including Brushed Nickel Faucet, |
Waterdrop WD-G3-W | $$$ | RO | 550-2,200 gal | 58 | ~$115 | Quickest Filter Change |
Epic Smart Shield Undersink Filter | $ | Inline | 650 gal | 42, 53, 401 | $110 | Simple Under Sink System Designed to Filter the Water on Demand |
Crystal Quest 1000C & 1000CP | $$ | RO | Varies | – | ~$100-155 | |
Aquasana AQ-5200, AQ-5300 & AQ-5300+ | $ | Separate Faucet | 800 gal | 42, 53, 401, P473 | $160 | 3 New Faucet Designs Including Brushed Nickel, Filters Last Six Months |
Culligan US-EZ-1 vs. US-EZ-3 vs. US-EZ-4 | $ | Extra Faucet | 500 gal | 42, 53 | ~$120 | |
CuZn UC-200 | $ | Inline | 50,000 gal | 42 | – | Ease of Installation, Filters High Amount of Water |
Woder 10K-Gen3 & Woder 10K-DC | $ | Inline | 10,000 gal | 42 | – | Easier to Install Than Competition, Long-Lasting |
The following are things worth considering before you go out and buy a high quality water filter system to install under your kitchen counter. These are also the very same criteria we focused on when picking our top products for this guide.
Almost every water filter does a great job at reducing chlorine and improving overall water aesthetics, which is a good start. But what about the really bad stuff, say some heavy metals and pesticides for example?
Truth is, not all water filters are created equal. When directly compared, some are way more effective at filtering certain kinds of contaminants than others. Thus, there are big differences in the level of water purity they can provide.
By checking for important NSF/ANSI certifications, you can make sure that a certain filter or filter system is able to remove all or at least the majority of harmful substances your water may contain. What certifications to focus on? Standard 42, 53, 401 and 58 (RO systems only).
There is carbon filtration, there is reverse osmosis (RO), there is ion exchange. Different water filters use different technologies and media to help you get rid of impurities in your water. And while reverse osmosis units produce the best possible results, it might be more efficient for your water conditions to install a filter that’s much more simple.
Usually, the best approach is to test your water as a first step. As soon as you know what you are facing, you can go out and find an appropriate filter.
Although there are exceptions, the general rule is that the more filter stages a system has, the higher is the quality of treated water it provides.
The downside is that the more stages, the higher maintenance costs and the bulkier the filter system.
Non-RO under sink water filtration systems don’t come with a storage tank. So the water gets filtered on demand. The thing is, nothing is more annoying than having to wait a whole day to fill a single glass of drinking water. #exaggerate
But seriously, pay attention to water flow rates measured in gallons per minute (gpm). Besides, low flow also means low water pressure.
A standard kitchen faucet that has no water filter attached to it delivers somewhere around 2.0 gpm (Source). The lowest flow rate we could find with an under sink filtration system was 0.25 gpm.
Meanwhile, you should note that thorough filtration requires time. This is why the Aquasana AQ-5300 for example, which features very sophisticated filtration technology, provides no more than 0.5 gallons of water per minute.
When you can actually install a home water filter system yourself, you save quite a bit by not having to call a plumber. The good news is that most under sink purifiers fall under this category – even if you don’t have any prior experience. Some don’t even require the use of tools, except maybe for an adjustable wrench to tighten the fixings.
If a filter comes with a separate faucet rather than featuring an in-line design, the installation process can be more difficult, but not too much. For this type, you will have to drill an extra hole somewhere in your counter in case your kitchen sink doesn’t have a spare one.
By the way, the advantage of using a separate faucet is that you don’t have to purify every drop of water you use. Only water used for direct consumption gets filtered. This will help you to save time and money in the long run. How? It’s simple: Your filters are going to last way longer. On the other hand, if all the water is being processed, the filters will reach their capacity a lot sooner.
One of the main benefits of under sink water filters is that they are easy to maintain, so less for you to worry about. The reason is that the amount of water gallons that a filter cartridge can handle before it needs replacement is relatively high.
One of the filters we reviewed above has a really high capacity of 50k gallons. If your household uses 3 gallons of filtered water per day, 50,000 will last you for more than 45 years – at least in theory. Because water filters are also limited by how long you can use them. This is due to the fact that bacteria might grow inside the filter media after months or years of use.
Also, keep in mind that filtration capacities are ideal values. Depending on the conditions in your home, such as feed water quality, a filter might never actually reach that benchmark.
The amount of work required to maintain a water filter system also depends on how well it was designed. Twist on/off filters can be changed in under 2 minutes. Filters with housings can be a pain in the a**.
Some under counter water filters are larger than you’d think. If you have unlimited space in your sink cabinet, this doesn’t really matter. However, if you don’t, this should influence your final buying decision.
Also, don’t forget that reverse osmosis water filter systems use their own storage tank.
In terms of costs, you have to take into account the initial purchase plus recurring expenses for replacement cartridges, which start to add up in the long term. This is when high filtration capacities with fewer changes really pay off.
In all our under sink water filter reviews, we also estimated annual filter replacement cost for each system.
More on Under Sink Water Filters
An under sink water filter is a piece of equipment that can be used to purify the water at a single outlet in the home, usually the kitchen sink.
Under sink water filters are made of one or more filter stages that can use a variety of filter media. Most common is activated carbon, but there’s also ion-exchange resin, KDF, reverse osmosis membranes, catalytic carbon, sediment filters, and a few other.
The greatest benefits of installing an under sink filter in your home is improved water quality – ideal if you’re facing excessive chlorine, lead, or PFAS for example.
Generally speaking, under sink filters are easier to install and maintain than you might think. And they’re affordable, too! So, what are you waiting for?
In this section, we’ll briefly explain how an under counter water filter works, which isn’t overly complicated:
First of all, we need to differentiate between inline filters and those that come with a separate faucet.
Simple under sink water filters feature just one stage of filtration. This could mean that the water treatment process isn’t very thorough, but it doesn’t have to. Some water filter systems in this category, such as the Epic Smart Shield, work just fine and are very well capable of filtering the majority of a whole arsenal of contaminants from water.
Conventional under sink systems with two or more filters usually combine a sediment filter, which traps dirt, rust, sand and other larger particles, with carbon filtration. The latter can be granular carbon or one or more carbon block filters. Activated carbon is great for neutralizing bad tastes and odors, and also to adsorb chemicals like chlorine and VOCs.
If you’re dealing with heavy metals you should consider a filter using KDF or anion exchange media.
Most reverse osmosis drinking water systems get installed under the kitchen sink, so we decided to include them in our reviews and buying guide. There are a few differences when compared to regular under sink water filter systems:
Honestly, anyone who’s having tap or well water quality issues should consider buying an undersink water filter.
If your water smells or tastes unpleasant, there’s an under sink filtration system for that.
If your water is contaminated with lead, there’s a filter for that.
If your water contains pesticides due to agricultural runoff, there’s a filter option…
Don’t worry, under sink water filter system installation is nowhere near as difficult as installing a whole house filter system. What’s more, in most cases you don’t have to make any permanent changes to your plumbing. However, each model might need a slightly different approach. Thus, take these instructions as a general guideline and always make sure to consult the product manual carefully!
As with its installation, you don’t need to be a licensed plumber in order to maintain an under sink water filter properly. In most cases, all that’s required is timely and regular filter change (and maybe some cleaning).
Check the product manual to find out how often you have to replace the filters of your specific setup. Annual or biannual filter replacement are the norm. Although with well water, more frequent filter changes might be required especially with elevated sediment levels and water hardness.
That said, replacing under sink water filters should be a matter of minutes:
Under sink and countertop water filters are both popular. Here’s a list of their similarities and differences.
When compared to countertop water filters, under sink units are quite similar. They come as single-stage and as multi-stage units. You can also find reverse osmosis systems in both categories.
Again, not much of a difference. There are so many filter models on the market that you’ll find extremely low and extremely high filtration capacities in either group.
Size and installation is where under sink or countertop filter does make a difference. First of all, while countertop water filters are highly compact for obvious reasons, under sink systems can be somewhat larger in size – not all of them, mind you.
Furthermore, countertop filters are mostly installation-free. They’re either autarchic or can be attached to any standard-sized kitchen faucet in under five minutes. Under sink filters on the other hand need to be properly installed.
Countertop and under sink filters are pretty similar when it comes to filter replacements.
Questions? Ask away!
And remember: We’ll keep hunting for the best under sink water filters, adding new under sink water filter reviews to this article occasionally. So come back!