Best Under Sink Water Filters of 2021

If you're ready for unlimited pure drinking water with less effort, cost, and waste - an under-sink filter is the logical next step. 

Brian Adee, Senior Writer

David Lewis, Chief Editor

Last Updated:

If your household drinks more than a gallon of filtered water per day, an under sink water filter can offer the best bang for your buck — and the best tasting water — of any type of filter.

In this guide, we’ll be using over 100 hours of research, comparison, and testing to closely examine each under sink water filter available today. By the time you’re finished, you’ll have a clear picture of which is the best under sink water filter for your home and your budget.

Our Top Picks

Combining excellent filtering power with a high capacity and great flow rate, the AQ 5300 is the gold standard in under sink water filters.

Smaller and more affordable, the AQ 5200 has the most top-notch filtration certifications of any under sink system.

Our Under Sink Water Filter Picks

A Detailed List of Best Under Sink Water Filters

The best under sink water filter for you will depend on what exactly you’re looking to change about your water. It will also depend on what’s most important to you, from filtering capacity to size and space requirements to water pressure.

With that in mind, we’ve broken down our list into nine different under sink water filters, each with its own unique benefits. 

1. Aquasana AQ 5300 – Best Overall

Aquasana AQ-5300 Under Sink Water Filter System
$159.99

The AQ-5300 system is our top pick for under-sink water filters. Its top-notch filtration certifications, huge filtering capacity, and excellent flow rate make it more than capable of providing an entire household with an endless supply of clean, healthy, great-tasting drinking water.

Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 12:51 pm GMT

Of all the water filter brands that we’ve researched and tested, Aquasana consistently ranks as the most versatile and reliable. And if you’re looking for the best filter for the widest variety of situations, the AQ 5300 should be your first stop. Its certifications are exceptional, and the filter capacity and flow rate are top-notch. Though it’s a little bit pricier than some household budgets may like, you’re paying for industry-leading performance and reliability.

What We Like
  • Excellent ANSI certifications
  • Better flow rate than almost any other under sink filter
  • High filter capacity can provide for even the highest use households
  • Easy filter replacements with clear indication of when to replace
What We Don’t Like
  • If you don’t get it on sale, it’s quite a steep investment
  • Filter replacements are pricier than smaller systems
  • Requires installation of a separate faucet
  • Takes up quite a bit of room under the sink

Certifications

The AQ 5300 under sink water filter system has three certifications from the NSF/ANSI: 42, 53, and 401. Let’s take a closer look at why that’s important.

Certification 42 is the most common value that you’ll find in water filters. It means that the filter is rated for “aesthetic impurities” — or in other words, it will improve the smell and taste of your water. In short: No more chlorine taste or smell in your drinking water.

Certification 53 protects you from consuming contaminants that have a detrimental effect on human health. This includes lead and mercury, as well as common chemicals and solvents from pesticides and manufacturing.

Paired with certification 401, this means that the AQ 5300 is incredibly thorough at removing harmful contaminants from your water. That’s because certification 401 is a special case: It’s rated for “emerging contaminants” like pharmaceutical runoff. 

Take all of that together, and you have a filter that removes 99% of up to 77 contaminants in your water. 

Filter Capacity

The average capacity for an under sink water filter cartridge is 500 gallons. While that’s enough for most households, large or heavy use households may notice a drop in their water quality before it’s time to replace the filter.

The AQ 5300 filters, on the other hand, have a filter capacity of 800 gallons through their 6-month life span. That’s more than enough to provide drinking and cooking water for a family of four. So if you’re looking for a filter that will provide complete filtration no matter how much water you’re using, the AQ 5300 is a great choice.

There’s a caveat here, though: Even with its larger capacity, these filters still have the same lifespan as smaller capacity filters. You’ll need to replace them every 6 months, and they’re a little bit more expensive than standard filters. 

So if you’re not using close to the full volume in that time period, another system will prove more economical. That means while a family of four that uses this filter for cooking and drinking water would benefit, a single household or couple wouldn’t likely see any benefit.

Flow Rate

If you’ve ever been bothered by a slow-running filter, the AQ 5300 will impress you. It has a flow rate of .72 gallons per minute — Meaning that it is 50% faster than the next best under sink water filters.

This means that it’s easier to use this filter for everything in your household, from filling jugs of drinking water to boiling water for pasta or soup. In practical terms, the higher flow rate means you’ll be able to fill a 12 oz glass of water in under 4 seconds, or an 8 quart stock pot in a little under 3 minutes. While it’s not absolutely necessary to have this high of a flow rate, it’s a significant quality of life improvement for anyone who uses a lot of filtered water.

The Verdict: The AQ 5300 is the most efficient and complete under sink filter system we’ve found.

2. Aquasana AQ-5200 – Best Value For The Price

Aquasana AQ-5200 Under Sink Water Filter System
$95.00

If you're outfitting a small kitchen with clean water, the AQ-5200 is an incredibly efficient use of your under cabinet space. The filter’s body is compact and easy to install, and the costs are quite reasonable. 

Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 12:38 pm GMT

The smaller and more affordable version of our best overall under sink water filter performs nearly as well, with only minor differences. In exchange for a slightly lower flow rate, you’ll get the same excellent certifications and easy filter replacement at a much lower price. And since it’s smaller than the AQ 5300, it can fit in even the most cramped of kitchens, too.

What We Like
  • Impressive performance for the price
  • Excellent certifications for water purity
  • Small enough to fit in almost any home
  • Easy filter changes
What We Don’t Like
  • Slower flow rate than our #1 pick
  • Smaller filter capacity than leading competitors
  • May not be great for homes with large families
  • Still requires installation of a dedicated faucet

Affordable Performance

For right around $100, the AQ 5200 is an impressive piece of equipment. Its flow rate and filter capacity are easily enough for two people living in a home, or for a larger family that only uses their filter for drinking water. 

And since it uses Aquasana’s proprietary filter technology, this under sink water filter is rated to remove 99% of 77 different contaminants. In short, what you get out of this is great tasting, healthy water — without breaking the bank. Plus, when you’re ready to replace the filters every 6 months, it’s as simple as twisting the old filters off and screwing a new filter on. No specialty tools are needed.

Compact

For the quality of filtration that the AQ 5200 offers (more on that in a moment), it’s amazing that it can fit in such a small package. If you’ve avoided getting an under sink water filter system because of a lack of space, this is the filter for you. It’s about half the size of standard 3-stage systems.

But even if you can fit a larger filter system under your sink, do you really need to? The larger the filters that are provided, the greater their cost per replacement. That’s another benefit of the AQ 5200: Its filters are about 30% less expensive than what you’d need to replace on a larger system.

Excellent Certifications

Just like the larger AQ 5300, the Aquasana AQ 5200 is tested and certified to NSF/ANSI Standards 42, 53, and 401. This means that it’s fully capable of removing:

  • Aesthetic impurities
  • Contaminants known to harm your health
  • Emerging contaminants, like pharmaceutical runoff

This all translates to: The AQ 5200 will make your water exceptionally pure, with a great taste and neutral smell.

FYI: The AQ 5200 and 5300 make an excellent pair. If one doesn’t suit your needs, the other one likely will.

3. Aquasana Claryum Direct Connect – Easiest Installation

Aquasana Claryum Direct Connect Under Sink Filter
$99.99
Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 12:20 pm GMT

Completing the range of under sink filters from Aquasana is the Claryum Direct Connect. It has what might be the fastest and easiest installation process of any under sink water filter. By connecting directly to your existing water line, it removes the necessity for installing a separate faucet. That gives it an excellent flow rate, and pairs nicely with Aquasana’s always-stellar certifications. The only potential downsides? It lacks a sediment filter, and it takes up quite a bit of space under the sink.

What We Like
  • Fast and easy to install
  • Excellent filtering certifications
  • High flow rate
  • Easy filter changes
What We Don’t Like
  • Large size (20.5 by 4.5 inches) means it may not fit under your sink 
  • No pre-sediment filter means if your water is high in sediment, it can clog
  • Replacement cartridges are fairly pricey
  • Some owners report a loss of water pressure

Fast and Easy Installation

If the idea of punching out a hole to add a new faucet is outside of your DIY comfort zone, the Claryum Direct Connect is a great alternative. Simple tools and clear instructions mean that anyone can install this on their existing water line in about an hour.

Even better, you don’t need to mount the Claryum Direct to the walls under your sink. It can lay on its side, or you can install a few brackets to save space on the floor of your cabinets.

And when you’re ready to change the filter cartridge after 6 months, it’s even easier than the installation. A simple twist-off, screw-on design means you can replace the filter in under a minute.

In short: It’s the easiest Aquasana filter to install, and requires little more than time and following directions.

Excellent Filter Certifications

You may have noticed by now that our top three recommendations are from Aquasana. Why? Because they offer some of the best filter certifications of any brand. And just like their larger filter systems, the Claryum Direct Connect is certified for standards 42, 53, and 401.

So even though it’s easier to install, you’ll get the same great-tasting and contaminant-free water that each other Aquasana filter provides.

High Flow Rate

Because it attaches directly to your existing water line, the Direct Connect has the highest flow rate of any Aquasana filter. It offers up to 1.5 gallons per minute of filtered water. That’s up three times as much as comparable filters that require a separate faucet.

Pro Tip: Always measure under your sink before deciding which water filter is right for you. The Claryum Direct Connect measures 20.5 by 4.5 inches, so make sure you have the space for it.

4. AO Smith 2-Stage – Best For Small Spaces

AO Smith 2-Stage Under Sink Clean Water Faucet Filter
$99.00
Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 12:17 pm GMT

Compare the A.O. Smith 2-stage filter to the Aquasana AQ 5200, and you’ll notice more than a few similarities. That’s because A.O. Smith is a direct copy of Aquasana’s compact under sink filter — but it’s a Lowes-exclusive brand.

Depending on availability, A.O. Smith’s 2-stage filter may cost less, more, or exactly the same as the AQ 5200. So for most people, it’s an affordable and compact option for under sink filtration. If you’re looking to save space without compromising on the quality of your water, it’s an excellent alternative.

What We Like
  • Small and compact
  • Excellent filtering certifications
  • Affordable
  • Easy filter changes
What We Don’t Like
  • Installation requires good DIY skills
  • Lower flow rate than larger filters
  • Somewhat small filter capacity
  • Not great for high water use households

Compact Size

At just 8.75 inches tall and 4 inches wide, the A.O. Smith 2-stage filter is one of the smallest and most compact under sink filters around. If you’re tight on space and don’t want to sacrifice under-sink storage, it’s a fantastic choice.

In fact, we can’t think of a single sink cabinet that this filter wouldn’t fit into. Unless you have some seriously strange plumbing, there’s room for an A.O. Smith filter.

Excellent Certifications

Rated to reduce 99% of 77 contaminants, the A.O. Smith 2-stage filter boasts an impressive array of ANSI/NSF certifications. It’s designed to standards 42, 53, and 401. And that means it effectively reduces or removes dangerous contaminants, bad smells and tastes, and emerging contaminants like pharmaceutical residues.

In summary: For such a tiny filter, this does one heck of a job of cleaning and purifying your water.

Great for Small Homes and Apartments

The only downsides to having a smaller filter are its lower flow rate and filtering capacity. But if you’re living in a small apartment by yourself, or sharing a home with one other person, neither of these is an issue. Combine that with affordability and excellent performance, and you have a great filter for small homes and apartments.

Pro Tip: The A.O. Smith 2-stage under sink filter and the Aquasana AQ 5200 are carbon copies. The only difference is where each is sold, so shop around for the best price.

5. Home Master Hydroperfection – Best Warranty

Home Master HydroPerfection Undersink Reverse Osmosis Water Filter
$443.77

The Home Master TMHP Hydroperfection is a big investment, but it offers a level of water quality that’s downright impressive. Even murky well water is no match for 9-stage filtering.

Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 01:26 pm GMT

If you’re willing to invest in a pricier water filter system, it’s natural to want to make sure that it’s built to last. And while most filter systems offer 1 or 2-year warranties, the Home Master HydroPerfection has a best-in-class 5-year warranty. Combine that with excellent customer service and long-lasting filters, and you get real peace of mind by investing in the HydroPerfection.

What We Like
  • Extra long 5-year warranty
  • Only replace filters once per year
  • Responsive and helpful customer service
  • Remineralization stage gives great tasting water
What We Don’t Like
  • Difficult installation process
  • Fewer certifications than our top recommendations
  • Large initial investment
  • Water waste isn’t environmentally friendly

Warranty and Support

Here’s the deal: You’re going to have an exceptionally difficult time finding a longer warranty than with Home Master. At five years of full coverage, they’ll make sure you’re happy with your under sink filter system every step of the way.

And if owners’ reports are any indication, Home Master’s customer support is top-notch. They have dedicated phone lines for customer support, for everything from installation to troubleshooting and filter replacement.

9-Stage Filter With Remineralization

So here’s the big question mark: The Home Master HydroPerfection hasn’t yet pursued ANSI/NSF certifications. Usually, this would be a deal-breaker for us. 

But upon closer inspection, their filtration system is the real deal. Nine stages, including reverse osmosis and a remineralization phase, ensure that your water will be healthy and great tasting. And it is rated to remove 99% of the big three contaminants: Lead, chlorine, and iron.

And it’s about as environmentally friendly as a reverse osmosis system can get, with a 1:1 wastewater to freshwater production ratio.

Long-Lasting Filters

Almost every under sink filter system requires filter changes every 6 months. But the HydroPerfection offers double this longevity, with filter replacements needed only once per year. If you want a filter system that’s as low maintenance as possible, Home Master is the way to go.

The Low Down: Though it’s pricier and requires more installation know-how, the Home Master HydroPerfection offers an incredible warranty and long-lasting filters. It’s a long-term investment that will pay off in the end.

6. Epic Smart Shield – Most Environmentally Friendly

Epic Smart Shield Under Sink Filtration System
$130.00
Buy Now
We earn a commission if you make a purchase, at no additional cost to you.

While any water filter will reduce plastic water bottle waste, only Epic has made it their mission to create the most eco-friendly under sink system. Compostable packaging, a water filter recycling program, and partnership with the Inland Ocean Coalition really set the company apart. And that’s all backed up with excellent certifications and long-lasting filters. The only real downside is the lack of a dedicated sediment filter — so check if your water is high in sediment before purchasing.

What We Like
  • Eco friendly through the entire lifecycle of the filter
  • Excellent filtering certifications
  • Easy installation and filter replacement
  • Long filter life
What We Don’t Like
  • No sediment filter = possible clogs
  • Fairly bulky, so it may not fit under every sink
  • Not everyone will have an eligible recycling center for rewards
  • Included tubing could be longer

Eco Friendly

Every Epic filter will remove the need for about 1500 single-use plastic bottles. That would be reason enough to buy one for the environment — but the company goes so much further with their commitment to being eco-friendly.

They’re a partner with both the Inland Ocean Coalition and 1% for the planet. That means Epic is helping to raise awareness of the problems of plastic in the ocean, and then actively doing something about it by donating part of their profits from each sale.

Add that to 100% compostable packaging and recyclable filters, and you have the most eco-conscious under-sink filter available on the market today.

Excellent Filtering Certifications

In addition to its environmentally-conscious outlook the Epic Smart Shield performs just as well as our favorite Aquasana filters. That means it’s certified to NSF/ANSI standards 42, 53, and 401.

Which means: The Epic Smart Shield will protect you from known and emerging contaminants, all while making great-tasting and neutral smelling water.

Long Filter Life (And Recycling Rewards)

Another part of what makes the Epic Smart Shield eco friendly is its long lasting filters. A single person using their filter may only need to replace it every 14 to 16 months, while a couple can expect to replace their filter just once per year. That’s both convenient and eco-conscious.

The Verdict: Though the system and filters are pricey, the Epic Smart Shield is an environmentally conscientious and top quality filter system.

7. 3M Filtrete – Best For Taste & Smell

3M Filtrete Quick Change Under Sink Water Filter
$34.99

The 3M Filtrete Water Filter is an affordable way to remove unpleasant tastes and smells from your water.

Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 01:09 pm GMT

Sometimes, you just want your water to taste and smell better. And preferably, you can have that without needing to drop $100, $200, or more on a filter system. 

If that describes your case, then 3M’s Filtrete system is a perfect fit. It’s inexpensive, certified to reduce aesthetic impurities, and very easy to install. In fact, it’s an excellent way to test whether a filter will make for more enjoyable drinking water. Then if you’re looking for further health benefits, you can upgrade to a more complete system later.

What We Like
  • As affordable as filters come
  • NSF/ANSI certified to improve the taste and smell of water
  • Easy to install
  • Easy to replace filters
What We Don’t Like
  • Only removes aesthetic impurities
  • Some owners report low water pressure
  • Compression fitting may leak after long use
  • Somewhat short filter life of 6 months

Maximum Affordability

Because it’s only meant to remove aesthetic impurities, the 3M Filtrete system is extremely affordable. For less than $50 and a few hours of your time, you can quickly and definitively improve your water quality. That makes it one of the best ways to test out whether an under sink system is right for you, with minimum financial risk.

Certified to Remove Bad Tastes and Smells

Being certified to ANSI/NSF standard 42 means that the Filtrete system is guaranteed to remove aesthetic impurities from your water. If your water is cloudy, or smells and tastes like chlorine, this filter will fix it in no time.

Easy Installation and Maintenance

Because it attaches directly to your existing water line, the 3M Filtrete system can be installed by anyone. The included directions are clear and well-illustrated, and common household tools are all you’ll need to get the job done.

Then when it comes time to replace the filter, you won’t need any tools at all. Just turn the filter a quarter-turn, remove it, and screw the new filter on. 

The Low Down: The 3M filter is the cheapest way to improve the taste and aroma of your water, but it doesn’t do much to improve the health qualities of your water. Still, it’s a great way to get started with water filtration on a tight budget.

8. APEC WFS-1000 – Longest Lasting Cartridge

APEC WFS-1000 Under-Sink Water Filter System
$118.95

Apec’s American-made filters have some of the largest capacity of any under sink filter. Since they last up to a year or more, the system is extremely affordable over time.

Buy Now
We earn a commission if you make a purchase, at no additional cost to you.
11/28/2021 01:30 pm GMT

The largest cost of any water filter system ends up being the filter replacements. The more often you need to replace them, and the more expensive new cartridges are, the more you’ll spend to have clean drinking water. 

So if you’re looking for the best bang for your buck long-term, the APEC WFS-1000 is the right choice. The extra long-life filters are surprisingly affordable, leading to a low-maintenance design that will save you a lot of money. If it had slightly better filtering certifications, it would have easily been our top recommendation overall.

What We Like
  • Extra-long filter life of 1 year or more
  • Certified to remove smells, tastes, and common contaminants
  • 100% U.S. made and manufactured
  • Affordable filter replacements
What We Don’t Like
  • Involved installation
  • Requires separate faucet
  • Certifications could be more robust
  • Large enough that it won’t fit under every sink

Excellent Value Over Time

With filters that last for a minimum of 1 year, and cost only about $30 to replace, the APEC WFS-1000 represents a huge savings over time. Compare that to other filters that last for about 6 months and can cost upwards of $50, and it’s easy to see how much more affordable this system is.

Good Filtering Certifications

Being certified to ANSI/NSF standards 42 and 53 means that the APEC WFS-1000 is great at removing bad tastes and odors, as well as common contaminants. It lacks the 401 certifications for emerging contaminants that made our overall top picks really stand out, though.

Low Maintenance Design

Once you have the system installed with a little DIY know-how and household tools, you won’t have to touch your APEC filter for a year or more. And when it is time to replace the filter, a simple twist-off design makes it easy to add your new filters and get back to drinking great-tasting water.

Pro Tip: Because of its long-lasting and affordable filters, the APEC WFS-1000 is one of the most affordable under sink filters for long-term use.

9. Clearly Filtered 3-Stage – Highest Filter Capacity

Clearly Filtered 3-Stage Under Sink Water Filter System
$500.00
Buy Now
We earn a commission if you make a purchase, at no additional cost to you.

If your house uses a lot of filtered water, most systems will fall short of their promised 6 months or 1 year between filter changes. That’s because their filtering capacities usually measure between 500 and 800 gallons. 

But if you’re using more than that on a regular basis, the 2000 gallon filter capacity of the Clearly Filtered under sink system is the best choice for you. It’s expensive, but it offers the largest filtering capacity of any system we’ve seen — all while having outstanding filtering certifications.

What We Like
  • Best in class filtering capacity
  • Excellent filtering certifications
  • Easy filter replacement
  • Easy installation
What We Don’t Like
  • Expensive base unit
  • Expensive filter replacements
  • Large cost of filtering over time
  • That’s it. It’s expensive.

Huge Filtering Capacity

This one’s entirely straightforward: The Clearly Filtered under sink system’s filtering capacity is up to 4 times as much as their competitors’ filters. Rated for one year of use and 2000 gallons of water, it’s the premier choice for high water use households.

Excellent Filtering Certifications

Just like our top recommendations, this filter system meets ANSI/NSF standards 42, 53, and 401. That means it’s fully capable of removing all aesthetic impurities, common contaminants, and emerging contaminants. So in short, it makes the cleanest and best tasting water a filter can produce.

Easy Installation and Replacement

Unlike other systems with this degree of filtration, the Clearly Filtered under sink system is remarkably easy to install. Give yourself 10 minutes to read the directions and 20 minutes to install it, and you’ll be set up and ready to go. Then when you’re ready to replace filters, it’ll take only a few minutes at most.

The Verdict: Clearly Filtered’s 3-stage under sink system has some of the most impressive statistics of any system we’ve considered — including a big price tag for both initial investment and filter replacement. But if you’re going through a lot of water in a year, there’s no other filter that can handle the same volume as this one.

Methodology – How We Determined Which Under Sink Water Filter Is The Best

In comparing under sink water filters, we’ve identified 10 criteria that separate the best from the just okay. Understanding these will give you the insight necessary to choose for yourself which water filter is the best fit for your needs.

Certifications

If I can only pass on one piece of advice for choosing a water filter for your home, it’s this:

It has to be certified by the American National Standards Institute (ANSI) and the National Sanitation Foundation (NSF). If it’s not, there’s no guarantee that the filter actually does what its manufacturer says it does.

The reason you should rely so heavily on ANSI/NSF certification is that they make their testing information publicly available. With that degree of transparency, you can know exactly what you’re getting out of your water filter. And that lets you pick and choose the common contaminants that you want to remove from your house’s water.

NSF’s guide to home water treatment is a complete resource for understanding the quality and purity of your water. This includes a full list of filters that meet or exceed contaminant reduction claims. 

But for us, the most important part of NSF’s guide is their list of numbered protocols for water filter testing. Water filters can be certified to one or more of these protocols, offering different filtering benefits. 

These are the statistics that you’ll see advertised with top quality water filters, so let’s briefly cover the three you’ll see most often:

  • NSF/ANSI 42 filters reduce “aesthetic impurities”. This means they’re well equipped to filter out odors and tastes from chlorine, but not other contaminants.
  • NSF/ANSI 53 filters reduce a contaminant that has a detrimental health effect. Carbon filters are the most common example, as they can be used to filter lead and other volatile organic compounds (VOCs).
  • NSF/ANSI 401 filters reduce emerging contaminants, a category of impurities that is not yet federally regulated. Pharmaceuticals are the best example of an emerging contaminant, which means that 401 filters are incredibly thorough.

Whenever possible, we’ll prominently display the NSF/ANSI certifications for each filter we review.

Type of Filter

Each of the certifications above can be given to a different type of under sink water filter. And depending on the filtration method used, you’ll notice wide variation in price, size, and performance.

Let’s take a closer look at the types of filtration used for under sink water filters.

Adsorption

Activated carbon is the most common material used for filtration, and it is an adsorption method. This means that water passing through the filter material will release its contaminants into the material’s surface. The longer the water is in contact with the filter material, the cleaner it will become.

Adsorption filters are usually the most cost-effective method of under sink filtration. They work quickly, produce no waste water, and can be paired with other filters for complete water purity. Overall, they’re an excellent choice for most homes.

Reverse osmosis (RO)

Reverse osmosis filter systems work by pushing water through an extremely fine membrane under great pressure. This takes time and requires a storage area for the filtered water, but leads to exceptionally pure water.

Additionally, RO systems are often paired with a carbon filter in a multi-stage process. They’re among the hardest systems to install on your own, but can offer a degree of filtration that’s hard to match with any other type of under sink water filter.

Ultraviolet (UV) light

The least common method used for an under sink water filter is ultraviolet light. Filters equipped with this technology can fully inactivate or kill bacteria and viruses. This can make your water safer to drink, but it offers little or no benefit to the taste and odor.

That’s why UV filters are usually paired with an adsorption or RO filter. Taken together, stacking multiple filtration methods like this can lead to completely purified water.

Ultrafiltration (UF)

Like RO systems, ultrafiltration uses a membrane to remove contaminants from water. But unlike RO, ultrafiltration still retains the beneficial minerals that are naturally present in water. In essence, they offer the same level of water purity while maintaining the natural taste of your water.

Additionally, UF filters produce no waste water in their purification process. As a result, they also have a tendency to filter slowly and may have a negative impact on flow rate and water pressure.

Size and Capacity

An under sink water filter’s size and capacity are directly related to the type(s) of filtration it employs. The more complex and layered the filtration system, the more space it will take up under your sink.

Of course, one of the big advantages of an under sink water filter is that it doesn’t take up counter space or fridge space. So for this criteria, it’s cut and dry: Either the filter will fit under your sink, or it won’t.

We’ll provide the dimensions for each filter system we review. Then, you can compare these measurements to the measurements you take under your own sink.

Flow Rate and Water Pressure

The filtration method used for an under sink water filter will also affect how quickly it dispenses water. If your home already has low water pressure, choosing a filter that won’t negatively affect it will save you a lot of headaches.

Adsorption filters usually offer the least reduction to flow rate and water pressure. Reverse osmosis filters will almost always slow down your faucet’s ability to dispense water. Ultrafiltration systems fall somewhere in the middle — not as fast as adsorption filters, but not as slow as reverse osmosis.

It’s worth noting, though, that the specific design of a company’s water filter has a big effect on flow rate and pressure. Because of this, it’s better to consider each filter individually and examine any information they have about relative flow rates and pressure. We’ll include that information with each review whenever it’s available, and let you know if the company makes no claims about it.

Water Waste

Reverse osmosis filters have fallen out of favor with environmentalists for one simple reason: They produce a fair amount of water waste to create fully purified water. This can also lead to higher water bills, increasing the total cost of using a reverse osmosis filter system.

In contrast, other filtration methods produce little or no water waste. Because of this, you’ll see a definite preference in our reviews for adsorption filters over reverse osmosis filters.

Filter Life 

The time between filter changes is a big reason to go for an under sink water filter system. Compared to countertop or pitcher filters, an under sink water filter will last up to 12 times as long between filter changes.

Of course, this also comes with a higher cost per filter replacement. We’ll be looking specifically at the cost of filter replacement over time, and comparing that to other filter options to decide which offers better long-term value.

Ease of Installation

Professional plumbing installation can be costly and time-consuming. That’s why we greatly prefer filter systems that are easy to install with a little time and a can-do attitude.

In each review, we’ll note the relative ease of installation as well as any special tools or equipment you might need. The simpler the better.

Warranty, Support, and Parts Availability

Unlike a pitcher filter, an under sink water filter is always a long-term investment. The upfront costs are higher, which means that it needs to last a long time to get your money’s worth.

For each water filter we review, we’ll note the length of the warranty and how easy it is to get help with installation and parts replacement. The longer the warranty the better. And the easier any maintenance or part replacement is, the better.

Long Term Costs

When all is said and done, the primary benefit of an under sink water filter is its ability to provide as much clean, pure drinking water as you want. And it should do this for a very long time to offset the initial investment.

We’ll take a close look at the cost of each filter system over time. This includes filter replacements relative to time and/or number of gallons. Then, we’ll compare this to the average cost of other types of filter systems.

Recap

We hope that by now, you have a good working understanding of the variety of under sink water filters available to you. After taking a thorough survey of your own needs and desires, matching up with the right water filter should be easy peasy. And with our thorough vetting and dozens of research hours, you’ll be able to find the filter that’s available at the best price, too.

But we have one more trick to share with you as well: Under sink water filters often come with a deep discount if you buy them on Black Friday or Cyber Monday. So if you’re looking for the absolute best possible price, check out our deals page and sign up for email notifications.

Frequently Asked Questions

To wrap things up, let’s take a look at the most commonly asked questions about under sink water filters. This should give you a full and rounded look and remove any lingering doubts you have about whether a water filter is right for you.

Why should I get an under sink water filter?

Under sink water filters offer an excellent combination of complete filtration and long life spans, with the convenience of never having to refill a pitcher. They’re a larger initial investment than a pitcher filter, but will usually end up being a more economical choice in the long run. So if you’re committed to drinking and cooking with water that’s as pure as possible, an under sink water filter is the right choice for you.

How do I know what’s in my water?

If you’re hooked up to municipal water, your local water utility/authority can give you a water quality report. Also known as a consumer confidence report, or CCR, this provides a detailed list of exactly what’s in your water.

If you’re not sure whether that’s accurate, or draw your water from a well, you’ll need to pursue independent testing. The EPA’s Water Lab Network is where you’ll want to find a certified lab to do so.

Do I need electricity for my water filter?

The majority of water filters do not require electricity to operate. The exceptions to this are UV filters and some distillation filters. But all of the under sink water filters featured in the above review can operate without electricity.