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Best Under-Sink Water Filter Systems of 2024

Scott Winfield
Written by Scott Winfield
Last Updated on

Many water filter systems are large, bulky, and hard to install. That’s where under-sink filter systems come in.

These systems are compact, easy to install, and can comfortably be fitted out of sight under your kitchen sink. Still, it can be difficult to decide which is the right filter for your home. That’s why we put together this list of the best under-sink water filter systems of 2024.

Our top pick is the Clearly Filtered 3-Stage Under the Sink Water Filter System. We were impressed with its superior contaminant removal capabilities, multiple NSF certifications, and its high filter capacity.

Water Filtration System for Sink Reviews

Clearly Filtered 3-Stage Under the Sink Water Filter System

Clearly Filtered 3-Stage Under-the-Sink Water Filter
  • Type: 3-stage filtration
  • Contaminants Removed: 232+ contaminants, including sediments, heavy metals, VOCs, sodium fluoride, asbestos, radiation, and lead.
  • NSF Certification: NSF Standards 42, 53, & 401
  • Filter Capacity: 2,000-gallon for each filter
  • Warranty: 30-day worry-free trial, limited lifetime warranty

PROS

  • Removes more than 232 contaminants with great success, making it one of the most effective under-sink water filters available
  • Very easy to install for DIYers and compatible with any type of faucet or sink
  • It’s low maintenance, its filters are easy to remove, and they only need to be replaced around once a year
  • Has three different NSF certifications so you can trust it to reliably remove contaminants from your water
  • It’s designed to retain beneficial minerals in your water while removing harmful contaminants. This leads to a balanced mineral content for healthy drinking water
  • Minimum wastewater

CONS

  • Some customers have reported that their cold water pressure dropped after the system was installed
  • Although the filters don’t need to be replaced very often, they are expensive to replace when the time comes
  • The filter isn’t equipped with any smart tech to give you updates on maintenance requirements and performance

The under-the-sink filter system by Clearly Filtered is our favorite since it can remove more than 232 different contaminants. In that sense, it’s the most powerful under-sink filter on the planet that’s been independently tested. When you consider its unprecedented contaminant removal success rate, it comes at a reasonable price.

Plus, its sleek design makes it the perfect choice if you’re looking for a capable filter that takes up little room. Let’s take a look at some of its key features.

3-Stage Filtration

So, why is this system so effective at removing contaminants? Well, it’s because of its innovative filters that subject the tap water to three stages of purification: an advanced priming filter, a second filter that specifically targets heavy metals and VOCs (volatile organic compounds), and a built-in fluoride filter.

The advanced priming filter, which is actually Clearly Filtered’s sophisticated take on coconut carbon pre-filters, reduces the number of sediments in the water. This process prepares the water for further stages of filtration while also getting rid of its nasty odor, bad taste, and color.

In the second stage, another advanced filter is employed to minimize the chemical hazards present in both municipal water systems and well water with great success. It reduces herbicides, pesticides, radiation, and heavy metals such as arsenic (by 94.3%), lead (by 98.9%), and manganese (by 99.9%), as independently tested following NSF standards.

However, what really stood out for us is the built-in fluoride filter of the third stage, which is a great alternative to traditional reverse osmosis filters. Unlike reverse osmosis filters, it doesn’t eliminate beneficial minerals or waste a lot of water during the filtration process. Moreover, its fluoride removal ratio of 90.7% is superior to what most reverse osmosis filters on the market are capable of (80% to 90%). So, if you’re reluctant to get a reverse osmosis filter because you fear it’ll remove the beneficial minerals, this system could provide a good alternative for you.

We should also note that it might sometimes decrease the water pressure by 20%. Still, when the filtration process is this good, we can forgive a slight drop in pressure.

Easy To Install

Afraid that such great filtration means an arduous installation process? Don’t be! Anyone can DIY-install the Clearly Filtered in under fifteen minutes with the help of a wrench.

Additionally, the unit is compatible with any kind of sink and faucet, doesn’t require power to work, and all of its filters are twist-off and need to be replaced only once a year. So, both its installation and maintenance are quite easy, which is another reason why it’s our favorite.

NSF Certification

Unfortunately, it’s fairly common for water supplies in the U.S. to contain high levels of lead, and this is one of the primary reasons it’s wise to invest in an under-sink water filter. To make sure it’s effective against lead, you want to choose a filter that meets the NSF/ANSI standard 42 for particulate removal and the NSF/ANSI standard 53 for lead removal, as stated by the CDC (Centers for Disease Control and Prevention).

This filter meets both of those standards. It’s been independently tested in a third-party lab to ensure it filters out lead and other heavy metals to the required levels. The NSF certification tells you that you can rely on this filter to remove contaminants without just taking the manufacturer’s word for it.


Aquasana SmartFlow Reverse Osmosis

Aquasana Smartflow
  • Type: Reverse osmosis
  • Contaminants Removed: 90 contaminants, including VOCs, heavy metals, lead, arsenic, and fluoride.
  • NSF Certification: NSF Standards 42, 53, 58, & 401
  • Filter Capacity: 13.32 GPD (gallons per day)
  • Warranty: 90-day guarantee, 2-year warranty

Sometimes, all we want in the space under our sink is a traditional filtration system that employs reverse osmosis and features a tank. The best item on the market that fits that criterion happens to be the Aquasana SmartFlow RO.

Although its capability to remove only 88 contaminants (see page 16 of the owner’s manual for the full list) is a bit underwhelming compared to the numbers the Clearly Filtered boasts, there should be no cause for concern. The SmartFlow Reverse Osmosis is capable of removing a majority of hazardous contaminants with a 99% success rate.

So, if you’re concerned about the presence of PFOA/PFOS, fluoride, lead, cysts, and other pollutants in your water, then we’d highly recommend giving this filter a go. Here are the features that caught our eye:

4-Stage Filtration

The first stage of the filtration process is pretty standard: an activated carbon filter that removes organic chemicals, including VOCs, herbicides, and pesticides.

After that, though, we’re introduced to Aquasana’s signature designs: The SmartFlow Reverse Osmosis Membrane and Claryum. The SmartFlow Reverse Osmosis Membrane is a unique design that can filter any dissolved solid material smaller than one micron. Think of it as a big net with holes big enough to let fresh water particles through but small enough to stop contaminant particles from getting through. Thanks to that, the levels of fluoride, arsenic, and radium that reach the faucet are significantly reduced.

Once the dissolved solids are taken care of, the water moves into the Claryum filter, which combines activated and catalytic carbon block techs in the same ion-exchange filter. This filter is capable of removing many sub-micron contaminants like heavy metals.

What’s more, Aquasana throws a remineralizer into the mix, retaining beneficial minerals usually lost through reverse osmosis. The SmartFlow RO adds healthy doses of potassium, magnesium, and calcium back into the water. In the end, the water isn’t only healthy but tastes great as well.

Easy to Maintain

Like the Clearly Filtered system, all the filters in the SmartFlow Reverse Osmosis are also twist-off. While the reverse osmosis membrane and remineralizer can last a year, all the other filters need to be replaced once every six months.

However, the installation process is where the Aquasana differs from the Clearly Filtered. It requires lots of tools and plumbing knowledge, so it’s better to employ professional help.

Also, its wastewater ratio is not the best, so the unit is not eco-friendly: for a cup of pure drinking water, it sends four cups down the drain.


Epic Smart Shield

Epic Smart Shield
  • Type: Single carbon block filter
  • Contaminants Removed: 70 contaminants, including heavy metals, chlorine, chloramine, lead, asbestos, microplastics, uranium, and fluoride.
  • NSF Certification: NSF Standards 42, 53, & 401
  • Filter Capacity: 651 gallons of filter life
  • Warranty: 100% lifetime warranty

For those looking for a portable under-sink water filtration system, there’s no better option than the Epic Smart Shield. Its single filter doesn’t weigh much, it occupies very little space, it’s incredibly easy to install and uninstall, and it’s suitable for almost every budget.

That doesn’t mean it’s less efficient in terms of purifying water, either. Similar to the high-end options above, it’s NSF-certified, and it can remove more than 70 contaminants from tap water with a 99% success rate.

Key Features:

  •  Effective contaminant removal: This includes heavy metals, agricultural contaminants, pharmaceuticals, chlorine, and chloramines. Its fluoride removal rate of 97.88% is even better than what the Clearly Filtered and the Aquasana SmartFlow have to offer
  • Retains beneficial minerals: Unlike the Aquasana SmartFlow RO, it doesn’t need to employ a remineralizer. The filtration system leaves potassium, calcium, and magnesium intact, so the water doesn’t lose its essential minerals during the purification process
  • Carbon block filter: The filter features a solid carbon block design, and it’s completely BPA- (bisphenol A) and lead-free. This is great as it gets rid of the risk of BPA and lead leaking into your water supply
  • High output: Despite its humble look when compared to other items on our list, it can produce 651 gallons of purified water over the span of one year. That number is equal to 1,500+ plastic water bottles
  • Eco-friendly: Its eco-friendliness isn’t limited to preventing plastic bottles from going to landfills. We particularly like the Epic Smart Shield because its filter is made of 100% recyclable materials. This means you’ll feel a lot less guilty when you have to replace its filter! The company is also a member of the 1% for the Planet project, and they even run their own recycling program. If you register for it and send them three used Epic Smart Shield filters to be recycled, you’ll receive a new filter for free!

Waterdrop G3P800

Waterdrop G3P800
  • Type: Reverse osmosis and UV sterilizer
  • Contaminants Removed: An unspecified number of contaminants, including TDSs, PFASs, VOCs, heavy metals, lead, bacteria, chlorine, and fluoride.
  • NSF Certification: NSF Standard 58
  • Filter Capacity: 800 GPD (gallons per day)
  • Warranty: 30-day guarantee, unspecified warranty

The Waterdrop G3P800 is pretty luxurious as far as water filters are concerned. It almost looks too nice for a filtration system that’s going to be tucked in under a sink, but more importantly, it’s super powerful in terms of removing contaminants. In addition, its water capacity of 800 GPD can easily accommodate large households, offices, schools, and even restaurants.

It’s the ideal choice if you’re looking for a reverse osmosis system with advanced filtration technology that still maximizes space efficiency.

Key Features:

  • First PP cotton layer: The first filtration stage aims to eliminate large particles and sediments like rust, sand, and nematodes with a polypropylene (PP) cotton filter
  • Scale inhibitor: Water scale can ruin clothes and kitchen appliances and give fruits and veggies a nasty texture after washing. The scale inhibitor membrane of the G3P800 reduces limescale formation to a significant extent
  • Activated carbon block filter: This filter reduces many dangerous metals like lead and chemicals like fluoride and chlorine. As a result, the taste and odor of the water are also improved
  • Second PP cotton layer: If there are any large particles left standing after the first three stages, the second polypropylene cotton filter makes sure they’re removed
  • Reverse osmosis membrane: Any impurity that’s larger than 0.0001 microns is filtered out by this highly efficient reverse osmosis membrane. The list includes total dissolved solids (TDSs), PFAS, and bacteria
  • Post-activated carbon filter: In the sixth stage, the post-filter ensures that no VOCs and chlorine make their way into the faucet
  • UV sterilizer: As the last line of defense, the Waterdrop G3P800 employs a UV sterilizer that has a sterilization rate of 99%
  • Tankless design: No tank means you don’t have to worry about bacterial formation
  • Easy installation: Any DIYer without prior plumbing experience can install it quite easily
  • Low maintenance: The filters and the reverse osmosis membrane only need to be replaced once every 6-12 months, depending on the usage. Waterdrop also includes a faucet with a smart LED screen on which the filtration process can be tracked, and any malfunction is reported. In that sense, it’s easy to maintain as well

 Frizzlife PD600

Frizzlife Tankless Reverse Osmosis System With Alkaline Remineralization - PD600-TAM3
  • Type: Reverse osmosis and alkaline remineralizer
  • Contaminants Removed: An unspecified number of contaminants, including TDSs, PFASs, VOCs, mercury, lead, asbestos, chlorine, and fluoride.
  • NSF Certification: Not certified
  • Filter Capacity: 600 GPD (gallons per day)
  • Warranty: Limited one-year warranty

The tankless Frizzlife PD600 is unlike any other filtration system on our list. It has a space-age look, and although it employs reverse osmosis like many of its counterparts, it aims to neutralize its negative effects with the alkaline remineralizer. That’s a breath of fresh air in this industry, and that’s why we liked it so much.

It’s best suited to those who want a reverse osmosis system that’s equipped with smart features for easy monitoring and maintenance and doesn’t take up much space.

Key Features:

  • 8-stage filtration: Its filtration process is quite similar to that of the Waterdrop G3P800—at least up until the last stage. The first six stages, including the 0.0001-micron reverse osmosis membrane, consist of many attempts to eliminate contaminants from the water. As a result, many dangerous chemicals (like arsenic, asbestos, and fluoride), heavy metals (like lead, mercury, and radium), VOCs, and TDSs are removed. If there’s any foul taste or odor to the water, it’s taken care of as well
  • Alkaline remineralizer: One of the reasons the Frizzlife PD600 stands out is that its remineralizer isn’t like the others. It’s an alkaline remineralizer that readjusts the alkalinity of the end product by bringing pH to its natural level above the 7.5 threshold. In the process, it also adds beneficial minerals like potassium and calcium back into the water
  • Smart features: It features a smart filter life reminder that leaves no room for doubt about when to replace filters
  • Eco-friendly: Filter replacement is eco-friendly — only the cartridge inside the plastic housing needs to be changed, which significantly reduces plastic waste in the long run.
  • Straightforward installation: The installation process is quite simple too. It’s pretty well laid out in the owner’s manual, and the product page on the Frizzlife website includes a video guide on installation

How We Reviewed Under Sink Water Filter Systems

When testing the under-sink water filters listed above, these are the criteria we adhered to:

  • How effective they were in removing contaminants,
  • Whether they were independently tested and NSF-certified,
  • What kind of filtration technology they employ,
  • How easy they were to install,
  • Whether they required high or low maintenance,
  • What warranty options the brands were offering,
  • And, of course, how much they cost.

Let’s revisit how our top five fared on each of these fronts as well as explain our benchmarks a little better.

Contaminants Removed

Unfiltered municipal tap water contains many contaminants that may present a hazard to our health either in the short or the long term. These include blatantly dangerous elements like VOCs, heavy metals, and disease-bearing bacteria, but also subtle threats like pharmaceutical or agricultural waste.

Therefore, the success of a water filtration system depends on its ability to remove as many contaminants as possible. Yet, there are a couple of questions we need to ask when it comes to contaminant removal numbers::

  • How can we be sure that they remove these contaminants?
  • Do the numbers that brands boast reflect the truth?

Well, the best products on the market, like our top three, are tested independently in labs that apply NSF standards, and they offer a full list of removed contaminants, including the removal success rate. Among them, the Clearly Filtered especially shines—it can remove 232+ contaminants with high removal success rates.

Some, on the other hand, like the last two products in our list, fail to provide customers with this assurance but are still effective against many contaminants. Both Waterdrop and Frizzlife claim that their products can remove more than 1,000 contaminants, but these claims lack any proof.

Water Filters (Best to Worst)Contaminants Removed
Clearly Filtered232+ (independently tested)
Aquasana SmartFlow Reverse Osmosis  90+ (independently tested)
Epic Smart Shield70+ (independently tested)
Waterdrop G3P8001000+ (not tested)
Frizzlife PD6001000+ (not tested)

NSF Certification

Founded in 1944 as a global and independent organization, the National Sanitation Foundation works to test, inspect, and certify whether our buildings, automobiles, food, and water are up to certain health standards.

In the industry of water filtration, tests conducted by NSF-approved labs help companies verify the effectiveness of their products, especially when it comes to removing contaminants. After the tests, some of these products get certified by the NSF.

The products we included in our top five had four different NSF certifications among them. Our #2, the SmartFlow Reverse Osmosis, has them all:

  • NSF 42:The NSF 42 certification means that a filtration system is able to remove basic taste-altering and odor-causing contaminants. It also entails chlorine as, more often than not, it’s the culprit for bad taste and odor in our water.
  • NSF 53: The NSF 53 is the most important of all certifications in the industry of water filtration as it directly pertains to health. It verifies the capability of the product to remove all the health hazards from the water.
  • NSF 58: Given only for RO systems, the NSF 58 certification simply signifies that the components of the RO filters are well within health regulations. Note that it doesn’t relate to the quality of the water in any sense but only to the materials the RO system is made of.
  • NSF 401: The NSF 401 certification verifies that the filtration system is capable of removing herbicides, pesticides, and pharmaceutical waste, as well as chemicals used in retardants and detergents.
Water Filters (Best to Worst)NSF Certification
Clearly FilteredNSF 42, 53, & 401
Aquasana SmartFlow Reverse OsmosisNSF 42, 53, 58, & 401
Epic Smart ShieldNSF 42, 53, & 401
Waterdrop G3P800NSF 58
Frizzlife PD600Uncertified

Filtration Technology

Nowadays, reverse osmosis is the most conventional method for filtering water. However, it’s also responsible for eliminating beneficial minerals along the way, which usually forces brands to include remineralizers in their filter systems. Moreover, the water purified by RO systems is generally more acidic than it should be.

Therefore, leading innovators of the industry are in search of alternative methods that have similar contaminant removal success to RO while retaining beneficial minerals. In that sense, the Clearly Filtered (#1) and the Epic Smart Shield (#3) are exemplary systems. Both have developed their own unique filtration tech that’s a worthy alternative to RO.

Speaking of uniqueness, the Claryum tech of the SmartFlow Reverse Osmosis and the alkaline remineralizer of the Frizzlife PD600 are also worth mentioning. The Claryum is capable of removing unprecedented levels of sub-micron contaminants. The Frizzlife alkaline remineralizer, on the other hand, offers a better alternative to traditional remineralizers like that of the SmartFlow RO.

Water Filters (Best to Worst)Filtration Technology
Clearly FilteredA unique 3-stage filtration
Aquasana SmartFlow Reverse OsmosisRO + Claryum + remineralizer
Epic Smart ShieldSingle carbon block filter
Waterdrop G3P800RO + UV sterilizer
Frizzlife PD600RO + alkaline remineralizer

Ease of Installation

If you want to save on installation, your filter of choice should be DIY-friendly and have a helpful owner’s manual. After all, nobody wants to damage their plumbing due to a bad manual.

In that sense, the Clearly Filtered is the best item on our list, thanks to its detailed guide. Anyone with no prior plumbing knowledge can install it in under 15 minutes with little more than a wrench.

The Aquasana SmartFlow RO, on the other hand, is the exact opposite of the Clearly Filtered. It requires someone with plumbing knowledge to install, and even with one, it might take longer than you’d like.

Water Filters (Best to Worst)Ease of Installation
Clearly FilteredDIY-level (>15 minutes)
Epic Smart ShieldDIY-level
Waterdrop G3P800DIY-level
Frizzlife PD600DIY-level
Aquasana SmartFlow Reverse OsmosisPlumber required

Maintenance Requirements

Some systems have filters that need to be replaced more frequently than others. Sometimes, even the filter replacement might require the presence of someone with plumbing experience.

Fortunately, though, none of the products on our list require high maintenance. The Frizzlife PD600, in particular, blows the competition out of the water in this regard, with its smart screen that tells you when to change which filter.

The Clearly Filtered and the SmartFlow Reverse Osmosis both have twist-off filters that can easily be replaced.

The only problem might lie with the Epic Smart Shield, whose filters cost almost as much as the whole system itself. However, if you register for their recycling program, you can get a new filter for every three used filters you send them.

Warranty

A good warranty reflects the company’s trust in its product. Plus, it can greatly reduce maintenance costs in the long run, so, it’s always going to be an important aspect of any purchase of a product that you aim to use for years, like a water filter.

In that sense, the 100% lifetime warranty of the Epic Smart Shield and the limited lifetime warranty of the Clearly Filtered is the absolute best you can get. On the other hand, the unspecified warranty policy of the Waterdrop G3P800 and the limited one-year warranty of the Frizzlife PD600 might be causes for concern.

Water Filters (Best to Worst)Warranty
Epic Smart Shield100% lifetime warranty
Clearly FilteredLimited lifetime warranty
Aquasana SmartFlow ROTwo-year warranty
Frizzlife PD600Limited one-year warranty
Waterdrop G3P800Unspecified

Price

Needless to say, a loaded price tag doesn’t always mean good performance. So it’s always better to think about a purchase in terms of the value you get for the money.

All things considered, the best-value under-sink water filter is the Clearly Filtered. Although it’s not exactly super affordable, it has all the important NSF certifications, and it’s one of the most powerful filters among the independently tested ones.

Water Filters (Affordable to Expensive)Price
Epic Smart Shield$135.00
Aquasana SmartFlow Reverse Osmosis  $224.99
Frizzlife PD600$469.99
Clearly Filtered$550.00
Waterdrop G3P800$999.00

Important: Please note that these prices were listed as of February 2024 and they’re subject to changes over time.

Frequently Asked Questions

We have covered all the important aspects you should consider when purchasing a new under-sink filtration system. However, there are additional specific questions that we can answer.

Which under-sink filter removes the most contaminants?

Although Frizzlife claims that its products can remove more than a thousand contaminants from the water, these claims aren’t supported by independently conducted tests. Nor are their filtration systems NSF-certified.
Among systems that have been independently tested and hold several NSF certifications, the Clearly Filtered is the most powerful contaminant remover with 232+. Moreover, its removal success ratio is quite extraordinary.

What is the average price of an under-the-sink filter?

A decent under-the-sink filter will cost about $300-500. However, there are also affordable examples like the Epic Smart Shield. Although it only costs a bit north of $100, it still produces healthy water.
The Waterdrop G3P800, on the other hand, would fall on the other side of the spectrum. Its seven-stage filtration system is surely something to behold, and its price tag of almost $1,000 reflects that.

What does installation require?

Installation requirements of under-the-sink filtration systems vary wildly from one product to the next. Whereas the Clearly Filtered can easily be installed just with a wrench, the Aquasana SmartFlow Reverse Osmosis requires professional plumbing.
More often than not, companies will include installation info on their websites and instruction manuals. It’s important to study them thoroughly in order not to mess up the plumbing and decrease the water quality while trying to improve it.

What is the average lifespan of the system?

A system can last for a lifetime, but its filters can’t.
You should replace the majority of carbon filters used in the making of home filtration systems once every six to twelve months. If the system is used in a commercial setting, you can do so every four to six months.
RO membranes and remineralizers, on the other hand, can serve their purpose for one to three years.
The best brands in the water filtration industry will let you know when the time for filter replacements comes. It’s best to heed their warnings.

Who are the best under-sink water filter brands?

The most prominent and trustable names in the industry are as follows:
Clearly Filtered
Aquasana
Epic Filters
iSpring
Waterdrop
Frizzlife
APEC

Conclusion

In almost all the important criteria we used to test the products above, the Clearly Filtered leads the race. Its tested contaminant removal results are unmatched, it has all the important NSF certifications, and it’s quite efficient for its cost.

However, if you’re in the market for a traditional RO system with a tank, the Aquasana SmartFlow Reverse Osmosis is the most reasonable option, thanks to its effectiveness and affordability. The Epic Smart Shield, on the other hand, is another affordable option, but it’s a portable and tankless one at that.

If you don’t care about NSF certifications and want to get the best in water filtration technology, the Waterdrop and Frizzlife models both present good options. While the Waterdrop aims to remove as many contaminants as possible with its RO filter and UV sterilizer, the Frizzlife remineralizes water as no other system does.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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