My 2024 Clearly Filtered Under Sink Water Filter Review

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We installed and tested the Clearly Filtered 3-Stage Under the Sink System on our city water supply in Colorado. Here, we’ve shared what we thought about the filter’s contaminant removal abilities, as well as how it improved our water quality, and its effects on our kitchen faucet water pressure.

🧾 Overview

The Clearly Filtered 3-Stage Under the Sink System is an under-counter water filtration system that’s hooked up to a cold water line and reduces 232+ of the most common drinking water contaminants. This under-sink three-stage filter removes more contaminants than any other similar system we’ve tested and is third-party tested and WQA certified for specific performance claims. Clearly Filtered definitely makes some bold promises for this system, and we were keen to try it ourselves and see how it performed in a real-life testing situation.

As a point-of-use system, the Clearly Filtered 3-Stage Under the Sink System is intended for filtering drinking water at a specific point in your home: your kitchen faucet. The idea is that the system intercepts your under-sink cold water line, and when you turn on the faucet, water flows through the three filter stages before traveling up the line for dispensing. The filter’s design means that it can be used with your existing plumbing – something we were pleased about, since we didn’t want the hassle of installing a separate faucet.

When we got the Clearly Filtered 3-Stage Under the Sink System to test, there was just one size and configuration available: the $550 three-stage model that measures about 15 inches tall. That’s around $100-$200 more expensive than similar models, but the Clearly Filtered system has been tested to remove hundreds more harmful contaminants, so there’s definitely an argument that the price is fair (of course, this depends on your budget). We could save a bit of money by signing up for the manufacturer’s Autoship subscription, which brought the upfront price down to $495 and reduced our spend on replacement filters by 10% (we could choose to get new filters every 9, 12, or 15 months). Our estimated annual spend on filter replacements was within $200.

Clearly Filtered 3 stage Under the Sink Filter Review

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In our testing, the Clearly Filtered 3-Stage Under the Sink System made a noticeable difference to our water’s taste, smell, and overall quality. In many ways, it reminded us of a reverse osmosis system, but without removing our water’s healthy minerals or wasting water during the filtration process. We’re planning to conduct a before-and-after lab test soon, so we can see exactly what this system is capable of removing from our water supply.

👍 What We Like

  • Tested to remove more contaminants than any other under-sink system we’ve reviewed
  • WQA certified
  • DIY-friendly install
  • Retains healthy minerals
  • Three separate filters allow for targeted contaminant removal
  • No need for a separate faucet

👎 What We Don’t Like

  • Expensive
  • Three separate filters to change
  • Only one size and flow rate

💡 First Impressions

Out of the box, the Clearly Filtered 3-Stage Under the Sink System is a tall, relatively slim unit with a simplistic, space-saving design. Our unit consisted of a filter housing bar, which the three separate filters attached to. Also included were two plastic push fittings, flexible inlet and outlet tubing, and screws (for if we wanted to mount the system on a wall).

Design-wise, as with many of the Clearly Filtered products we’ve tested, the Under-Sink Water Filter System is pretty basic. It definitely isn’t dressed to impress – we weren’t blown away by some of the high-tech features we see on reverse osmosis systems, like filter lifespan trackers and TDS readers. But our main priority was to remove as many contaminants from our water as possible without the negative side effects of RO, and in this respect, the Clearly Filtered system came through. We’ve tested enough water filters to know that the mark of a quality design isn’t necessarily the outside appearance.

Clearly Filtered says that all its products are individually inspected before shipping, and the Under-Sink Water Filter System is backed by a lifetime limited warranty. It was good to know that we could reach out to customer support if we felt that our filter system was defective (which, thankfully, it wasn’t).

Clearly Filtered Under Sink Filter installed under Brian's kitchen sink

🧪 Our Performance Testing

When it comes to performance, on paper, the Clearly Filtered 3-Stage Under the Sink System has more going for it than any other non-RO under-sink water filter system. It’s been tested to remove more than 230 contaminants, including contaminants that are notoriously difficult to remove, like arsenic and fluoride. Plus, Clearly Filtered says it should only reduce water flow by 20%, and as a bonus, the filter has recently obtained a WQA certification for its chlorine removal abilities (more on this later).

The purpose of our own testing was to determine whether the system was capable of living up to Clearly Filtered’s performance claims with everyday ongoing use. We haven’t yet been able to do a before-and-after water test to see which contaminants the system could remove from our tap water supply, but we’re planning this project for the near future, and we’ll update this review when that happens.

For now, our testing delved into the system’s performance across the following categories:

Our Water Quality

Our main reason for wanting to install an under-sink water filter system was to improve our water quality by removing contaminants, so here was where we wanted to be really impressed.

There are three filters in the Clearly Filtered Under-The-Sink Water Filter System:

  • The advanced priming filter, stage 1, is made from granulated coconut carbon and reduces chlorine, VOCs and chemicals that affect water’s taste and odor.
  • Filter stage 2, the heavy metals & VOC filter, uses a “special blend” that reduces pesticides, herbicides, arsenic, PFAS, and heavy metals.
  • The third filter, the fluoride and arsenic filter, uses Clearly Filtered’s “proprietary breakthrough fluoride reduction technology” that isn’t made from activated alumina or bone char, and isn’t reverse osmosis.

If, like us, your intention is to remove all the trace contaminants in your water, it makes sense to go with the Clearly Filtered Under-Sink system because it has been tested to remove more contaminants than its competitors. That means, regardless of what your water might contain, there’s a very good chance that the Clearly Filtered unit can effectively remove it.

But did we notice anything specific in terms of our water taste or odor?

As expected, given that the system has been certified for chlorine removal, we did. We noted that our filtered water tasted clean and pure, with a smooth mouthfeel. We couldn’t detect any chlorine tastes or odors.

Like all conventional filters, the Clearly Filtered unit retains healthy minerals, which meant we still had the taste benefits of these in our tap water, and our water’s pH wasn’t affected. Overall, we were impressed – the system did exactly what we’d expected it to do in this performance category.

Filtration Speed

As an under-sink system, the Clearly Filtered unit connects directly to your cold water line. This gives it an advantage over Clearly Filtered’s Water Filter Pitcher, which uses a slower and steadier gravity filtration process. With the under-sink system, we knew we’d have access to filtered water on demand from our faucet – but what kind of filtration speed could we expect?

Clearly Filtered doesn’t disclose the exact flow rate for this model. Generally, the other under-sink water filters we’ve tested in the past have a flow rate of between 0.5 and 1.5 GPM, so we expected the Clearly Filtered unit to be within this range. For some perspective, the average kitchen faucet has a flow rate of 2.0-2.5 GPM, so we did expect our flow rate to drop somewhat.

What we did know from the manufacturer was that the unit supposedly would only reduce our existing flow rate by 20%. We have a high-flow faucet, so we were skeptical. We decided to test Clearly Filtered’s claim by timing how long it took to fill a glass of water with our kitchen faucet on full, both before and after installing the system.

Pre-installation, our faucet filled a glass in about 4 seconds. The filling time doubled to almost 8 seconds post-filtration. So, the system didn’t quite live up to Clearly Filtered’s promises, but since our faucet is high-flow, this is understandable. 8 seconds is still pretty fast, and the speed of filtration didn’t drop too significantly as the filters became clogged over time – we could still fill a glass in around 10-12 seconds even towards the end of the filter lifespans.

Clearlyfiltered under sink direct connect system

Performance Longevity

According to the manufacturer, the lifespan for all three filters in the under-sink system is up to 2000 gallons (or 7500 L).

Considering the average person drinks about half a gallon of water per day, you should be able to get plenty of use out of the filters before changing them. Clearly Filtered recommends changing the filters once a year if you’re a small family; once every 15 months if you’re a single user; and once every 9 months if you’re a large family. For our 2-person household, they lasted 12 months – but did they continue to offer a high-quality performance right up to the end of their lifespan?

We knew that our water quality and how much water we used per day from our kitchen faucet would affect how long our filters would last, as with any filtration system. Remember, water filter manufacturers can only provide an estimated filter lifespan based on their interpretation of the average household water usage and quality, which could be different from your own.

In our own experience, we found that the filters worked well for the first 9-10 months. After this, the flow rate started to drop quite a bit. By month 12, while the filters were still usable, we knew it was time to swap them out for a new set.

In all, we were pleased with the system’s performance longevity, especially given that many similar under-sink water filters we’ve tested have a shorter 6-month capacity.

📑 Filter Testing & Certifications

If you like to see evidence that a water filter has third-party proof to support its performance claims before you make a purchase, you’ll be pleased to know that the Clearly Filtered Under-Sink Water Filter System has been independently tested to reduce or remove more than 232 contaminants, including chlorine, fluoride, chromium-6, lead and other heavy metals, pesticides, PFAS, and pharmaceuticals. The manufacturer has obtained testing from EPA-accredited laboratories for its performance, and the results are viewable online.

One of the complaints that we previously had about this Clearly Filtered model was that it didn’t have any official performance certifications. Yes, third-party testing is reassuring, but we wanted Clearly Filtered to take that extra step towards credibility, especially given the scope of contaminants that the manufacturer claims its system can remove.

The good news is that the under-sink filter system has recently obtained a WQA performance certification to NSF/ANSI Standard 42, to reduce chlorine taste and odor, so Clearly Filtered is taking a step in the right direction. We’re hoping that they’ll pay for additional certifications in the future – we’d love to see an NSF 53 certification for the reduction of contaminants with health effects, like lead and PFAS. We hope Clearly Filtered didn’t just apply for the NSF 42 certification to check a box, since performance certifications are a real mark of trust from a customer’s perspective.

The system also has a WQA certification to NSF/ANSI Standard 372, which isn’t related to performance – it just confirms that the unit is made from lead-free materials.

To see the full list of contaminants reduced by the Clearly Filtered Under-Sink Water Filter, check out the table below.

Contaminant% Reduction
Chloramine>95.30%
Chlorine>98.58%
Sodium Fluoride>90.65%
Aluminum>99.50%
Arsenic94.27%
Barium99.84%
Beryllium>98%
Cadmium>96.71%
Chromium (hexavalent)>99.67%
Copper99.96%
Iron97.08%
Lead>99.34%
Manganese>99.90%
Mercury (inorganic)>91.80%
Nickel>98.56%
Zinc>99.02%
2,4-D>99.53%
2,4-DB>99.96%
2,4,5-T>99.93%
2,4,5-TP (Silvex)>99.43%
3,5-Dichlorobenzoic Acid>99.65%
Acifluorfen (Blazer)>99.77%
Bentazon (Basagran)>99.74%
Chloramben>99.64%
Dalapon>99.96%
DCPA di-acid degradate>99.77%
Dicamba>99.93%
Dichlorprop>99.93%
Dinoseb>99.81%
Glyphosate>99.99%
Picloram>99.74%
Quinclorac>99.77%
8:2 Fluorotelomer sulfonate (8:2FTS)>99.81%
Perfluorobutane sulfonate (PFBS)>99.81%
Perfluorodecanoic acid (PFDA)>99.62%
Perfluorohexane Sulfonate (PFHXS)>99.81%
Perfluorohexanoic acid (PFHxA)>99.62%
Perfluorononanoic acid (PFNA)>99.62%
Perfluorooctane sulfonate (PFOS)>99.81%
Perfluorooctanoic acid (PFOA)>99.62%
Polytetrafluoroethylene>99.81%
Acenaphthene>99.72%
Alachlor (Lasso)>99.98%
Aldrin>99.79%
Alpha - BHC>99.80%
Atrazine>99.90%
beta-BHC>99.80%
bis(2-Chloroethyl) ether>99.81%
Bromacil>99.80%
Butachlor>99.80%
Butylate>99.76%
Carbofuran>99.88%
Chlordane>99.80%
Chlorneb>99.80%
Chlorothalonil (Bravo)>99.80%
Chlorprophane>99.81%
Chlorpyriphos>99.80%
Cis - Chlordane>99.80%
Cyanazine (Bladex)>99.80%
delta-BHC>99.80%
Dichlorvos>99.81%
Dieldrin>99.79%
Diphenamid>99.80%
Disulfoton>99.80%
Endosulfan I>99.77%
Endosulfan II>99.76%
Endosulfan Sulfate>99.81%
Endrin>99.84%
Endrin aldehyde>99.78%
Endrin Ketone>99.80%
Ethoprop>99.80%
Fenamiphos>99.81%
Fenarimol>99.80%
Fluridone>99.80%
Heptachlor>99.79%
Heptachlor Epoxide>99.80%
Hexachlorobenzene (HCB)>99.80%
Hexachlorocyclopentadiene>99.80%
Lindane>99.80%
Methoxychlor>99.80%
Metolachlor>99.80%
Metribuzin>99.80%
Molinate>99.80%
N-Nitrosodimethylamine (NDMA)>99.80%
p,p' - DDD>99.77%
p,p' - DDE>99.82%
p.p' - DDT>99.83%
Pentachlorophenol>99.80%
Polychlorinated biphenyls (PCBs)>99.04%
Propachlor>99.80%
Simazine>99.80%
Toxaphene>99.34%
trans-Nonachlor>99.80%
17-beta-Estradiol>98.99%
4-para-Nonylphenol>99.13%
4-tert-Octylphenol>98.59%
Acetaminophen>99.17%
Bisphenol A>99.01%
Caffeine>98.91%
Carbamazepine>98.60%
Ciprofloxacin>99.23%
Diclofenac Sodium>98.95%
Erythromycin>98.57%
Estrone>91.30%
Ethinyl estradiol>99.06%
Fluoxetine>98.95%
Gemfibrozil>98.97%
Ibuprofen>95.65%
Meprobamate>95.35%
Naproxen>90.48%
Primidone>98.98%
Progesterone89.42%
Sulfamethoxazole>98.98%
Testosterone79.17%
Triclosan>98.40%
Trimethoprim>90.00%
Butyl benzyl phthalate>99.80%
Di-n-butyl phthalate>99.80%
Di-n-octyl phthalate>99.80%
Di(2-ethylhexyl) phthalate>99.81%
Diethyl phthalate>99.80%
Dimethyl phthalate>99.80%
Gross Alpha (Thorium 230)>99.66%
Gross Beta (Cesium 137)>98.04%
2-Chloronaphthalene>99.80%
2-Chlorophenol>99.80%
2-Nitrophenol>99.80%
2,2-Dimethylphenol>99.79%
2,2'-Oxybis(1-chloropropane)>99.80%
2,4-Dichlorophenol>99.80%
2,4-Dinitrophenol>99.80%
2,4-Dinitrotoluene>99.80%
2,4,6-Trichlorophenol>99.80%
2,6-Dinitrotoluene>99.78%
4-Bromophenyl phenyl ether>99.79%
4-Chloro-3-methylphenol>99.80%
4-Chloro-phenyl-phenyl ether>99.80%
4-Nitrotoluene>99.79%
Acenaphthylene>99.80%
Anthracene>99.80%
Benzo[a]anthracene>99.80%
Benzo[a]pyrene>99.80%
Benzo[b]fluoranthene>99.81%
Benzo[g,h,i]perylene>99.80%
Benzo[k]fluoranthene>99.81%
bis(2-Chloroethoxy) Methane>99.79%
Chrysene>99.80%
Dibenz[a,h]anthracene>99.80%
Dinitro-o-cresol>99.79%
Diphenylamine>99.86%
Fluoranthene>99.80%
Fluorene>99.79%
Hexachloroethane>99.79%
Indeno[1,2,3-cd]pyrene>99.80%
Isophorone>99.80%
N-Nitrosodi-n-propylamine>99.80%
Nitrobenzene>99.80%
Phenanthrene>99.80%
Phenols>99.80%
Pyrene>99.80%
1,1-Dichloro-2-propanone>98.67%
1,1-Dichloroethane>99.89%
1,1-Dichloroethene>99.87%
1,1-Dichloropropane>99.84%
1,1,1-Trichloro-2-propanone>99.30%
1,1,1-Trichloroethane>99.88%
1,1,2-Trichloroethane>99.91%
1,1,2,2-Tetrachloroethane>99.88%
1,2-Dibromo-3-chloropropane (DBCP)>99.80%
1,2,3-Trichlorobenzene>99.30%
1,2,3-Trichloropropane>99.48%
1,2,4-Trichlorobenzene>99.79%
1,2,4-Trimethylbenzene>98.99%
1,3-Dichlorobenzene>99.80%
1,3-Dichloropropane>99.89%
1,3,5-Trimethylbenzene>98.94%
1,4-Dichlorobenzene>99.80%
2,2-Dichloropropane>99.00%
4-Isopropyltoluene>99.03%
Benzene>99.88%
Bromoacetonitrile>99.56%
Bromobenzene>99.20%
Bromochloromethane>99.87%
Bromodichloromethane>99.88%
Bromomethane>99.55%
Carbon Tetrachloride>99.89%
Chloroethane>99.64%
Chloroform98.38%
Chloromethane>99.81%
cis-1,2-Dichloroethene>99.94%
cis-1,3-Dichloropropene>99.87%
Dibromochloromethane>99.88%
Dibromomethane>99.46%
Dichloroacetonitrile>98.99%
Dichloromethane (methylene chloride)>99.45%
Ethylbenzene>99.89%
Ethylene Dibromide>99.78%
Fluorotrichloromethane>99.65%
Hexachlorobutadiene>99.80%
Isopropylbenzene>98.53%
m-Dichlorobenzene>99.80%
m-Xylene>99.88%
Monochlorobenzene (chlorobenzene)>99.87%
MTBE>99.86%
n-Butylbenzene>99.00%
n-Propylbenzene>98.93%
Naphthalene>99.79%
o-Chlorotoluene>99.00%
o-Dichlorobenzene>99.80%
o-Xylene>99.75%
p-Chlorotoluene>99.00%
p-Dichlorobenzene>99.80%
p-Xylene>99.88%
Sec-Butylbenzene>98.73%
Styrene>99.93%
Tert-Butylbenzene>99.01%
Tetrachloroethene>99.88%
Toluene>99.87%
Total trihalomethanes (TTHMs)99.59%
trans-1,2-Dichloroethene>99.87%
trans-1,3-Dichloropropene>99.87%
Trichloroacetonitrile>99.33%
Trichloroethene>99.94%
Vinyl chloride>99.77%
Xylenes (total)>99.75%

Check out the other Clearly Filtered systems in this review!

🔧 Installation & Maintenance Considerations

When it comes to installing under-sink systems, we’ve had mixed experiences in the past. Some, like RO systems, are challenging to install, and we’ve often resorted to hiring a plumber at an extra expense. So we were relieved to see that the Clearly Filtered system is designed to be easy to install, with just a few parts, no drain line, and no dedicated faucet. It’s also a non-permanent installation, so you can still use it if you’re renting.

The whole process took us less than 20 minutes from start to finish, and there were less than 5 steps involved. We just shut off our under-sink water supply, disconnected our cold water line from the cold water valve, and connected the inlet and outlet hoses. We then had to flush the system by leaving the faucet on for 3-5 minutes (we collected the water and used it to water our plants to avoid waste).

Check out our video review below to get a better feel for just how simple it is to install.

In terms of maintenance, we only had to think about the filters. We were pleased with the convenience of having the same lifespan for all three filters, so we could change them at the same time, rather than separately, as we’ve had to do with other under-sink systems.

We found changing the filters pretty simple, too – we just screwed the old filters off the housing bracket and screwed the new ones in place. We didn’t have to disconnect the entire system or use tools to do this. 

According to the user manual, the filters have a pretty flexible operation temperature of 38-85 °F, or 4-30 °C. As long as you don’t use the system outdoors, and you don’t connect it to your hot water line, the filters shouldn’t be affected by varying water temperatures within this range.

Clearly filtered under sink filter cold water line
Connected to the cold water line

Our readers get 10% off at clearlyfiltered.com 👉 Click here to get your coupon.

🤔 Is the Clearly Filtered 3-Stage Under the Sink Water Filter System Right for You?

In our opinion, the Clearly Filtered 3-Stage Under Sink Water Filter System is ideal for anyone who wants a performance-certified non-RO under-sink water filter that removes as many contaminants as possible from their tap water supply.

With that said, we don’t think the system is the best fit for everyone. It’s expensive, and the high price point mostly just reflects the fact that it has been tested to remove more contaminants than any similar under-sink filter. If you just want to remove select harmful contaminants from your water, this Clearly Filtered model may be unnecessarily advanced.

On the other end, if you want to purify your water, the Clearly Filtered Under-Sink System won’t do that. Only RO systems are capable of removing all water impurities, so you’ll need to upgrade if that’s what you’re after.

Our advice is to think carefully about your intended outcomes for water treatment, then decide whether Clearly Filtered’s offering meets your requirements.

Related: Clearly Filtered vs Hydroviv Comparison

  • Brian Campbell
    President & CEO, CWS, CWR

    Brian Campbell, a WQA Certified Water Specialist (CWS) and Certified Water Treatment Representative (CWR) with 5+ years of experience, helps homeowners navigate the world of water treatment. After honing his skills at Hach Company, he founded his business to empower homeowners with the knowledge and tools to achieve safe, healthy water. Brian's tested countless devices, from simple pitchers to complex systems, helping his readers find the perfect fit for their unique needs.

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