2020 Best Under Sink Water Filters: Under Counter Filtration System Reviews
Written by: Gene Fitzgerald // 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, do you? Well, you came to the right place!
1. Best Under Sink Water Filtration System: Clearly Filtered 3-Stage (*Non-RO)
In our opinion, the best under sink water filter system in 2020 is the Clearly Filtered 3-Stage. It has been repeatedly tested to remove/reduce well over 200 different water contaminants which is simply outstanding 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!
Coconut shell granular activated carbon filter removes chlorine (98.6%), chloramines (95.3%), taste, odor, cloudiness and colors, and volatile organic compounds and other common chemicals. Made in USA!
Special filter media blend reduces heavy metals like lead (99.9%) and chromium-6 (99.4%), pesticides, PFAS, radiological elements and more. Made in USA!
Last filter stage focuses on fluoride (99.5%) and arsenic (94.3%).
System is tested against NSF International standards 42, 53, and 401 for 230+ contaminants.
Some of the most thorough testing we have ever seen.
Healthy minerals are retained in the water adding to your daily nutritional intake.
Inline systems works with your existing faucet.
Features stainless steel inlet and outlet hoses for durability.
Easy to install. Non-permanent setup – ideal for renters – shouldn’t take more than 10 to 15 minutes.
Filters are modular, meaning they’re quick and easy to change without tools about once a year.
High capacity: 2,000 gallons.
Thanks to 30-day worry free trial, you can send back the under sink system for a full refund.
Expect 15 to 25 percent reduced water pressure.
High quality + domestic manufacturing mean relatively high price compared to some of the competition.
Replacements filters aren’t exactly cheap either. At least you can subscribe to Clearly Filtered’s VIP Program for 100% discount and free shipping.
2. The Runner Up: Epic Smart Shield Inline Under Sink Water Filter by Epic Water Filters
The Epic Smart Shield is our second most favorite non-RO (reverse osmosis) under sink filter system perfect for tap water and well water. It’s certified to remove chlorine/chloramine, lead, asbestos, cyst, E. Coli, and many other contaminants from water. Furthermore, it’s surprisingly affordable especially when compared to the Clearly Filtered 3-Stage system reviewed above and users love the great taste of the filtered water. 5 stars!
Areas with high sediment levels and people on well water are recommended to use additional 5-micron Epic Smart Shield sediment pre-filter to prolong filter life of Epic Smart Shield.
Removes more than 70 contaminants that might be lurking in your water.
Certified against NSF/ANSI Standards 42, 53, and 401 for chlorine taste and odor (95.5%), particulates, chloramine (95.5%), cyst (>99.99%), lead (>99.3%), VOC (99.6%), asbestos (>99%), mercury (>96.6%), MTBE, turbidity, bisphenol A, Estrone, Ibuprofen, Naproxen, Nonyl phenol, Phenytoin, and more.
Also tested for removal of E. Coli + Pseudomonoas Aeruginosa, PFOA + PFOS, microplastics, radiological elements, and several other.
Based on activated coconut carbon block filtration.
Very easy to install. Shouldn’t take more than 20 minutes even if you don’t have any prior plumbing experience due to inline design and quick-connect fittings.
Installation kit included (e.g. connector hoses, feed water adapter).
Inline meaning works with your existing faucet. But you can also purchase dedicated polished-chrome faucet kit.
Average filter life is 12 months (around 650 gallons). Annual cost: $110 which seems fair.
Join Clean Water Club and save 20% on replacement filters.
Filters are recyclable through company’s own recycling program. Collect 3 and mail them back to get a free filter as reward.
Really great customer support.
Water flow rate is 1.25 gallons per minute (gpm), so you might see water pressure drop.
3. Our #1 Under Sink Reverse Osmosis System: Aquasana OptimH2O
In our opinion, the number one under sink reverse osmosis system in 2020 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 water taste and balances the pH. All in all, an excellent offer. 4.5 stars!
Aquasana OptimH2O Reverse Osmosis Water Filtration System
4. Waterdrop WD-G3-W Tankless Under Sink RO Water Filter System
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.
5. Aquasana AQ-5200, AQ-5300 & AQ-5300+ Under Counter Water Filter Reviews
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
You have the choice between 3 faucet designs to match your kitchen décor.
System installation is easy. All necessary parts are included and the manufacturer instructions are precise (installation videos on YouTube!). No need to hire a professional plumber and spend a few hundred extra bucks.
Replace filters when they’ve reached their capacity limit or every six months, whichever comes first.
No need to shut off water supply thanks to clever filter design.
You’ll hear acoustic alarm and see red light flashing after six months. Takes out any guesswork.
AQ-5300+ is Bluetooth compatible and can be connected to free Aquasana app. App tracks time and estimates water usage to notify you about upcoming filter changes. You can also use it to order a new replacement filter.
Covered by one-year limited warranty.
Customer service is reliable
Filters feel rather expensive even if you sign up to the Water for Life program to receive a discount.
Reported problems with tubing popping out, broken filter housings, flimsy faucets, and failing O-rings.
May cause leakage.
Some reviewers complained about water pressure being way too slow.
6. Culligan US-EZ-1 vs. US-EZ-3 vs. US-EZ-4 Under Sink Filters
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!
7. Top Under Sink Filter System for Well Water: Crystal Quest 1000C & 1000CP
Crystal Quest’s 1000C and 1000CP are great 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.
12 stages of filtration remove sediments, water disinfectants, pesticides, herbicides, industrial solvents, VOCs, PCBs, microorganisms, taste, odor, heavy metals like iron, hardness, rotten egg smell, and much more.
Filter stage 1: Activated carbon block, 5-micron nominal. Adsorbs chlorine and all kinds of chemicals. Also traps undissolved matter to protect the rest of the system from fouling.
Filter 2: Ultrafiltration membrane, 0.02-micron. Reduces microorganisms and large organic/inorganics.
Filter 4: Granular activated carbon. Removes 99.9% chlorine taste and smell, and a bunch of chemicals.
Filter 5: Ion exchange resin. Targets metals and water hardness.
Filter stage 6 & 7: Eagle Redox Alloy media (copper-zinc blend). Removes hydrogen sulfide, chromium, cadmium iron, mercury, and other dissolved metals. Also prevents bacterial growth.
Stage 9: RO membrane. Rejects anything larger than 0.0001 micron.
Filter 11: GAC filter to remove residual taste.
Stages 3, 8, 10, and 12 are 1-micron filter pads. They remove suspended particles.
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 UC-200 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 is manufactured in the USA which is quite rare nowadays.
It’s bacteriostatic– meaning there’s almost no chance that bacteria or mold will grow inside the unit. This is a great benefit over regular carbon filters.
Filtration process: It’s a 3-stage combining micro sediment membranes and different filter media. Say goodbye to a range of organic and inorganic contaminants, such as chlorine, lead, herbicides, pesticides among others (not fluoride, sorry).
Essential minerals like calcium and magnesium are left untouched. This is good for your health, but bad for your coffee maker.
Filter installation is a breeze and will only take you a few minutes thanks to the simple design. If you don’t know how, CuZn provides a video with step-by-step instructions on their website.
3/8″ fittings are included. For non-standard plumbing, CuZn usually sends a special installation kit for free, so make sure to reach out to them.
No cartridge replacements required– simply set up the filter and forget about it for the next couple of years. Once the filter has reached the end of its lifespan you have to replace the entire unit.
Theoretically, you get a filtration capacity of 50,000 gallons or an equivalent of 5 years, whichever comes first. But it always depends on feed water quality. Just like most other under sink filter systems, the CuZn cannot handle hard water very well – one of the reasons to not use it on well water.
5 years warranty and 90 days satisfaction guarantee are part of the deal. If you don’t like how the filter performs, just send it back and get a full refund.
Some customers struggled with leaks, for example at the case of the unit. We also read about black grains that someone found in his water.
The good news: CuZn’s customer service is extremely responsive and helpful. The team is willing to take on any problem that users might have with the under sink filter.
9. Woder 10K-Gen3 & Woder 10K-DC Under Sink Water Filters
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-Gen3 and the Woder 10K-DC are among the best selling under sink water filtration systems on Amazon.
Compact in size.
Both use the same activated carbon filter media (NSF 42-approved). The following contaminants will be reduced/removed as per independent lab tests: 99.9% lead, 99.9% chromium-6, other heavy metals, 99.9% chlorine, VOCs, turbidity, and bad tastes and odors.
Enjoy healthier, crystal clear, and great-tasting drinking water right from the tap!
As far as filter installation goes, both units come with everything you need in order to set them up within minutes – literally. No expert skills required.
All you need to do is turn off the water supply under your sink, disconnect the cold water line and then install the filters’ inbound and outbound hoses (3/8″ by 1/4″). That’s it!
Filters are long-lasting and provide about 10,000 gallons or a minimum of 3 years when used on tap water. About 3 times as much as what you get with most other filters.
If your water contains a lot of hardness minerals like calcium or if it was processed by a softener before, the actual number of gallons might be a little lower.
Woder 10K-DC is a bit cheaper and must be replaced as a whole. The Gen3 features a smart head with a built-in valve which allows for changing the cartridge only. If you’re planning to use the Gen3 filter for long enough you’ll benefit from the smart head and save money in the long run.
Seller claims provided filtered water flow is 2 gpm. However, the filter itself is rated at 0.8 gpm. All in all, it would be nice to have a slightly faster flow rate.
Check our detailed reviews of the top reverse osmosis under sink water filter systems available on the market.
Buying Guide: What You Need to Consider When You Buy an Under Sink Water Filter
You have many, many options available when it comes to choosing a water filter system to install under your kitchen counter. In order for you to opt for a unit that suits your needs, our buyer guide will tell you what to consider:
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 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 (reverse osmosis filtration systems only).
There is carbon filtration, there is reverse osmosis, 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 filtered water it provides.
The downside is that the more stages, the higher maintenance costs and the bulkier the filter system.
Flow Rate & Water Pressure
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 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 purification technology, provides no more than 0.5 gallons of water per minute.
Under Sink Water Filter Installation
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 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.
Maintenance & Filtration Capacity
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, remember 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.
Under Sink Water Filter Costs
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 reviews, we also estimated annual filter replacement cost for each system.
More on Under Sink filters
What Exactly Is an Under Sink Water Filter?
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 taste and quality – ideal if you’re facing excessive chlorine or toxic lead 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?
How Under Sink Filters Work
In this section, we’ll briefly explain how an under counter water filter works, which isn’t overly complicated:
Inline vs. Dedicated Faucet
First of all, we need to differentiate between inline filters and those that come with a separate faucet.
As the name suggests, inline under sink water filters are installed in line, meaning they’re added to the existing cold water line of your kitchen sink. When you open the kitchen faucet, the unfiltered feed water has to flow through the filter system before it comes out all nice and clean. Water is filtered on demand.
Under sink filter systems with a dedicated faucet connect to the cold feed water valve, too, but from there they use their tubing to deliver the water. Many systems even come with their own storage tank to eliminate long waiting times.
Filtration Process: The Different Types
Single-Stage Under Sink Filters
Single-stage under sink 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 Multi-Stage Units
Under counter systems with two or more filters usually combine sediment filtration, which traps dirt, rust, sand and other large particles, with carbon filtration. The latter can be granular carbon or a carbon block filter. 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 and ion exchange media.
Reverse Osmosis Water Filters
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:
Under sink RO systems feature either a pressurized water storage tank or an electric water pressure pump, or both.
They come with their own faucet.
They require a drain connection. This is because reverse osmosis water filtration always produces wastewater, no matter how efficient the process.
Advantages & Disadvantages – Why You Should Install An Under Sink Water Filter
Installing an under-the-sink water filter system means a huge improvement in drinking water taste.
The filtered water tastes better because it’s higher quality overall. Simply put, it contains up to 99% less contaminants. Depending on the specific setup, this includes potentially harmful heavy metals, all kinds of chemicals, inorganic compounds, etc.
Speaking of setup, you can choose from many different products and opt for a system ideally suited for your needs.
Under sink water filters are designed to be compact.
What’s more, most are super easy to install and maintain – think filter replacements.
And when you move, the non-permanent installation allows you to take your filter system with you – great for renters.
Last but not least, affordability. Under sink filters are budget-friendly.
An under counter water filter provides water for one outlet only.
They’re quick to hook up, but unlike a pitcher, they aren’t installation-free. And if a system requires a separate faucet, you’ll have to drill a hole into your countertop or sink.
Who Should Buy an Under Sink Water Filter?
Honestly, anyone who’s having tap or well water quality issues should consider buying an under sink water filter.
If your water smells or tastes unpleasant, there’s an under sink filter for that.
If your water contains pesticides due to agricultural runoff, there’s a filter option…
How to Install an Under Sink Water Filter
Don’t worry, installing an under sink water filter isn’t difficult. 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!
Turn off the sink’s cold water supply.
Open the kitchen faucet to flush out any remaining water.
Disconnect the cold feed water line.
Mount the filter system to the side of your kitchen sink cabinet.
Connect the inlet hose of the under sink water filter system to the feed valve and tighten carefully.
Connect the outlet hose of the filter system to the faucet inlet hose. Tighten carefully.
Turn the cold water back on.
Flush the system for a few minutes or as long as specified by the manufacturer.
Maintenance – When Should I Change the Filter Cartridge?
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 replacements (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 replacements 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 the filter(s) should be a matter of minutes:
Close the water supply valve feeding the system.
Open the faucet to release pressure from inside the filters.
Remove the filter housings.
Discard the old filter cartridges, clean each housing with mild soapy water, and insert the new cartridges.
Screw the housings back with all O-rings properly seated.
Turn the water supply back on and make sure to check for leaks.
Under Sink vs. Countertop Water Filter Systems
Under sink and countertop water filters are both popular. Here’s a list of their similarities and differences.
Similarities & Differences
1. The Filtration Process
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 system in both categories.
2. Filter Capacity
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.
3. Size and Installation
Size and installation is where under sink vs. countertop water 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.
4. Filter Replacements
Countertop and under sink filters are pretty similar when it comes to filter replacements.
Frequently Asked Questions (FAQ)
Are under sink water filters worth it?
They are! Of course, not every under sink water filter is high quality, but a good filter system is designed to remove/reduce hundreds of contaminants from water.
How do you hook up a water filter under the sink?
Under sink water filter installation is not difficult at all. Inline units directly connect to your already existing sink faucet. Some filter systems, however, come with a separate faucet that might require you to do some drilling.
How do I choose an under sink water filter?
Most importantly, look for NSF certifications. They ensure that a certain water filter or water filter system removes all or at least the majority of harmful substances your water may contain. You should also pay attention to flow rates. Without a tank, water has to be filtered on demand. And you probably don’t want to wait two hours to fill one glass. Two more factors to consider are system size and maintenance (cost).
How do you clean an under sink water filter system?
It should be enough to clean your under sink water filtration system whenever you replace the filter elements. You can clean each filter housing with mild dish soap. Sanitize with bleach if need be.
How often should you change an under sink water filter?
This depends on the capacity of the filter elements. Long-lasting ones are good for thousands of gallons of water, others for a couple hundred.
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!
Gene Fitzgerald has been with BOS since the very beginning. She is head of content creation and has fully immersed herself into the home water treatment industry only to become an expert herself. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
Learn more about Gene and the rest of the BOS Team.