Best Under Sink Water Filters – System Reviews 2020 + Guide

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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 water 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!

On This Page You Will…

Under Sink Water Filter Best-Of List

ModelOur Rating$Tech/MediaFilter StagesExtra Faucet
Home Master TMAFC-ERP Artesian Full Contact Undersink Water Filter System

Best Rated Under Sink Water Filter System: Home Master TMAFC-ERP

Read Review
$$$Reverse Osmosis7Yes
Clearly Filtered Undersink Water Filter System

Most Effective (Non RO): Clearly Filtered 3-Stage

Read Review
$$$$Carbon Filtration + Specialized Media Blends3No
Woder 10K-Gen3 Undersink Water Filtration System

Best Seller: Woder 10K-Gen3

Read Review
$Carbon Filtration1No
CuZn UC-200 Undersink Water Filter System

Highest Filtration Capacity: CuZn UC-200

Read Review
$Carbon Filtration+ Oxidation3No
BACOENG UF Undersink Water Filter System

No Green Light for: BACOENG UF Water Filtration System


Best Under Sink Water Filter Reviews

1. Reverse Osmosis Under Sink Filter Systems

If you are looking for the best reverse osmosis under sink water filter system, here are our top picks:

Home Master TMAFC-ERP Artesian Full Contact Undersink Filter System

Best Rated Under Sink System: Home Master TMAFC

  •    Price: $$$
  •    Filter Process: 7 Stage
  •    Annual Costs: $$
  •    Extra Faucet:
  •    Installation: All Parts Incl.
APEC Essence ROES-50 Water Purifier for Kitchen Sinks

Most Cost-Effective: APEC Essence ROES-50

  •    Price: $$
  •    Filter Process: 5 Stage
  •    Annual Costs: $$
  •    Extra Faucet:
  •    Installation: All Parts Incl.
Olympia Water Systems OROS-50 Undersink Purifier System

Budget RO Under Sink System: Olympia OROS-50

  •    Price: $
  •    Filter Process: 5 Stage
  •    Annual Costs: $$
  •    Extra Faucet:
  •    Installation: All Parts Incl.

Home Master Filter System

  • Home Master’s TMAFC-ERP provides the purest water of all, thus making it the best under counter water filter. The system is made in the USA, backed by a 5-year warranty and comes with a permeate pump to reduce the amount of wastewater that goes down the drain by up to 80% – a real money saver! →Detailed review

APEC System

  • The APEC Essence ROES-50 is our second choice. 5 stages of filtration help you to get rid of sediment, lead, fluoride, arsenic, bacteria and lots of other nasty contaminants. The unit is always one of the best sellers on Amazon. Great value for the money. →Detailed review

Olympia System

  • The Olympia Water Systems OROS-50 is one of the most affordable RO systems while still providing quality water filtration. It has even earned NSF standards 42 and 58 certifications, which is a great start! →Detailed review

For even more RO systems, click here to get to our main guide.

2. Woder 10K-Gen3 & Woder 10K-DC Under Sink Water Filters

Woder 10K-Gen3 Undersink Water Filter

Best Seller: Woder 10K-Gen3

  •    Price: $
  •    Annual Costs: $
  •    Extra Faucet:
Woder 10K-DC Water Purifier for Kitchen Sinks

Woder 10K-DC

  •    Price: $
  •    Annual Costs: $
  •    Extra Faucet:


The Woder 10K-Gen3 and the Woder 10K-DC are among the best selling under sink water filtration systems on Amazon.

Both use the same activated carbon filter media, they are compact in size, and as their names suggest their filtration capacity is about 10,000 gallons or a minimum of 3 years when used on tap water. This is about 3 times as much as what you get with most other filters.

However, bear in mind that 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 lower.

The only difference between the two filters is that the Woder 10K-DC (which is a bit cheaper) must be replaced as a whole. The Gen3 on the other hand features a smart head with a built-in valve, which allows for changing the cartridge only.

In other words, if you use the Gen3 filter for long enough you will benefit from the smart head and save some money further down the road. By the way, replacement cost are super low.

Also, both filters are made with NSF 42-approved materials and can also be used in RVs.

What contaminants are removed?

  • 99.9% lead*
  • 99.9% chromium-6*
  • Other heavy metals
  • 99.9% chlorine*
  • VOCs
  • Turbidity
  • Bad tastes and odors

*as per independent lab tests

Looks like from now on you can enjoy healthy and great-tasting drinking water right from the tap!

As far as the filter installation is concerned, 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 attach the filters’ inbound and outbound hoses (3/8″ by 1/4″). That’s it!


  1. The seller claims that the 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.
  2. We miss additional certifications.

Our Verdict

What you want is unlimited access to refreshing and clean drinking water at home? Both Woder 10K 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!

3. Review: CuZn UC-200 Under Sink Water Filter

CuZn UC-200 Undersink Water Filter System

Highest Filtration Capacity: CuZn UC-200

  •    Price: $
  •    Filter Process: 3 Stage
  •    Annual Costs: $
  •    Extra Faucet:


Next on our list: The CuZn UC-200 inline water filter. A couple of things make it stand out:

  • It’s manufactured in the USA – which is quite rare nowadays.
  • It’s bacteriostatic – meaning that there’s almost no chance that bacteria or mold will grow inside the unit. This is a great benefit over regular carbon filters.
  • No cartridge replacements required – simply set up the filter and forget about it for the next couple of years.
  • It’s one of the top rated under counter water filter systems on the market.

Speaking of maintenance, theoretically, you get a filtration capacity of 50,000 gallons or an equivalent of 5 years, whichever comes first.

Why theoretically? Because 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.

Once the filter has reached the end of its lifespan you have to replace the entire unit.

What about the filtration process? It’s 3-stage combining micro sediment membranes and different filter media and everything is NSF certified against Standard 42 and/or 61.

It’s time to finally say goodbye to a range of organic and inorganic contaminants, such as chlorine, lead, mercury, herbicides, pesticides among others (not fluoride, sorry).

If you want to remove fluoride from your water supply, check out our fluoride special:

And although the filter system also removes unpleasant tastes and odors from water, essential minerals like calcium and magnesium are left untouched. This is good for your health, but bad for your coffee maker.

Furthermore, 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.

Lastly, a 5-year warranty and a 90-day satisfaction guarantee are part of the deal, so if you don’t like how the filter performs, just send it back and get a full refund.


Some customers had to struggle 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 is that 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.

Our Verdict

Water is supposed to taste like nothing. 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.

4. Aquasana AQ-5300 & Aquasana AQ-5300+ Under Sink Water Filtration Systems

Aquasana AQ-5300+ Water Filters

Aquasana AQ-5300+

  •    Price: $$
  •    Filter Process: 3 Stage
  •    Annual Costs: $$$
  •    Extra Faucet:
Aquasana AQ-5300 Filter for Water

Aquasana AQ-5300

  •    Price: $$
  •    Filter Process: 3 Stage
  •    Annual Costs: $$$
  •    Extra Faucet:


Up next we have 2 under sink water filter systems by Aquasana which are quite similar, namely the AQ-5300 and the AQ-5300+.

The latter provides 0.72 gallons of water per minute, about 50% more than what you get with the regular AQ-5300 (0.5 gpm). We know, 0.72 gpm doesn’t sound like much. But keep in mind that the more thorough the filtration, the lower the output water pressure and flow.

Other than that, the AQ-5300 is more compact in size thus requiring less space and the initial cost are lower, too. Also, replacement filters are more affordable.

Both systems feature a 3-stage purification process. Lifespan? Between 600 to 800 gallons:

  • Stage one: 20-micron sediment pre-filter
  • Stage two: Activated carbon
  • Stage three: Catalytic carbon

In total, 77 different impurities can be tackled. NSF certifications for Standards 42, 401, 53 and P473 guarantee excellent filtration performance for exceptionally pure drinking water for you and your family.

What’s more, the installation is relatively simple. All required bits and pieces are part of the package and instructions are very clear.

Above that, replacing filters about every 6 months or so can be done in no time and without the need to disconnect any water lines. Simply give the filters a quarter turn to twist them off and attach new cartridges the same way.

On a side note: An indicator light and an alarm sound will let you know when it’s time for the replacement, so no more guess work!

Last but not least, the AQ-5300 and AQ-5300+ are backed by a 90-day satisfaction guarantee as well as Aquasana’s superb customer service.


A handful of people had issues with leaks due to a leaky pre-filter, a faulty seal in the housing, or a hose that blew off.

Furthermore, replacement filters seem a bit pricey.

Our Verdict

Aquasana is known for building water purification systems with great filtration performance.

This, too, is the case for both the Aquasana AQ-5300 and the Aquasana AQ-5300+ which can even be used to overcome lead contamination. So if you want a water purifier that can provide you with exceptionally clean and delicious tap water, these are your ideal candidates.

5. APEC WFS-1000 Under Counter Water Filter

Aquasana APEC WFS-1000 Filter


  •    Price: $$
  •    Filter Process: 3 Stage
  •    Annual Costs: $
  •    Extra Faucet:


Assembled in the USA, the APEC WFS-1000 purifier for kitchen sinks can be used to treat tap water or properly disinfected well water.

We have 3 stages of water filtration that help you to get rid of sediment like dust and rust, chlorine, tastes, odors, volatile organic compounds and other chemical contaminants.

For fluoride and heavy metals, however, you will have to upgrade one of the two carbon block filters (more on that in a bit).

Also, most essential minerals are kept in the water, which is a real advantage as it adds to your daily nutritional intake.

Good water pressure and easy installation, although directions can be a little confusing at first. Still, even if you’ve never done any type of plumbing before, there’s no reason to worry thanks to the quick connect fittings and standard-sized tubing.

What about replacement filters? Made in the USA and last for about 12 months of use before they need changing – less work for you.

Speaking of filters, by default filter stages 2 and 3 are identical, which is why you might want to consider using a different cartridge for the latter. Just make sure that it’s standard-sized (10″) and you are good to go.

One of your options is a specialized fluoride filter. Others tackle chloramine or lead.

You also get a stainless steel faucet rather than a cheap one made from plastic and a 1-year satisfaction guarantee plus lifetime California-based support.


For more severe cases of contamination, this under sink water purifier won’t suffice. We are also missing certifications for contaminant reduction rates.

Our Verdict

If all your water needs is a finishing touch, by all means go for the APEC WFS-1000. It does what it says and because everything is standard-sized, you can choose from a wide range of cheap filter cartridges.

6. Clearly Filtered 3-Stage Under Sink Water Filter

Cleary Filtered 3-Stage

Clearly Filtered 3-Stage

  •    Price: $$$$
  •    Filter Process: 3 Stage
  •    Annual Costs: $$$$
  •    Extra Faucet:


One of the lesser known under-the-sink water filtration systems is the Clearly Filtered 3-stage which provides you with highly pure, safe and refreshing water right from your kitchen faucet.

All in all, the unit is capable of removing over 200 different contaminants (tested against NSF standards 42, 53 and 401). Here is an excerpt from the test report:

  • Chlorine (98.6%)
  • Chloramines (95.3%) – more information here and here
  • Sodium fluoride (99.5%)
  • Chromium 6 (99.4%)
  • Lead (99.9%) and other heavy metals
  • TTHMs (99.6%), PFOA (99,9%) and other chemicals
  • Dozens of herbicides and pesticides (99.9%)
  • More than a hundred VOCs and semi volatile compounds (99.9%)

These are excellent results!

Furthermore, you might be interested to hear that the under sink filter system is made in the USA, 100% BPA-free with stainless steel tubing, and very easy to install without the need for hiring a plumber or making any permanent changes to your plumbing system – great solution for renters.

On top of that, replacing filters is a piece of cake thanks to the twist on/off design. Plus, the product is covered by a lifetime warranty and you can return it within the first 30 days after purchase and receive a full refund in case you aren’t satisfied.


The Clearly Filtered under sink water filtration system is – there is no other way to say it – expensive. This might have to do with the fact that it is not imported from overseas, unlike many other units.

What’s more, new filters are not exactly cheap either. A small comfort is that you can subscribe to the Clearly Filtered VIP Program so that you get replacements automatically delivered on schedule and at a discounted rate.

Another minor drawback is that the system reduces water pressure by about 20 to 25 percent. To be fair, though, we have to remember that thorough filtration takes time.

Our Verdict

Our verdict: The best under sink water filter if you are willing to pay a premium for a premium product and premium water quality. Installation is a piece of cake. You will be more than happy with your purchase.

→ Read Our Full Review Here

7. 3M Filtrete 3US Filters

3M Filtrete Advanced 3US-PS01 Filter

3M Filtrete Advanced 3US-PS01

  •    Price: $
  •    Annual Costs: $$
  •    Extra Faucet:
3M Filtrete Maximum 3US-MAX-S01

3M Filtrete Maximum 3US-MAX-S01

  •    Price: $
  •    Annual Costs: $$
  •    Extra Faucet:


The 3M Filtrete 3US comes with three interchangeable inline filter variations with 6 months filter life. All reduce chlorine taste and odor, and sediments like sand, soil, silt and rust.

  1. The Standard 3US-AS01 is only really interesting if your water already has decent quality. It filters particles down to a size of 5 microns and is NSF Standard 42 certified. Filtering capacity: 2k gallons. Flow rate: 2 gpm.
  2. The Advanced 3US-PS01 filters all contaminants from water down to 0.5 microns including 99.99% of microbial cysts. Apart from NSF Standard 42, this filter has earned a Standard 53 certification. Filtering capacity: 2k gallons. Flow rate: 1.5 gpm.
  3. The Maximum 3US-MAX-S01 stands out as it removes 99% of all lead in addition to all the contaminants mentioned above.
    • Micron rating: 0.5
    • Standard 42 & 53
    • Filtering capacity: 1.5k gallons
    • Water flow rate: 1.5 gpm

For the installation, there’s no need to set up an extra faucet. The filtration system will easily connect to your existing one in less than 30 minutes.

Also, filters can be changed with a single twist in a matter of seconds – 100% hassle-free!


  1. Even with a new filter cartridge your water pressure may fall off quickly. Some people have complained about this.
  2. In rare cases, new filters had small cracks that caused water to spray everywhere.

Our Verdict

Standard, Advanced or Maximum, the 3M Filtrete 3US is very well received. It will make your water taste, smell and look much better.

However, it won’t stop everything from entering your glass, so if your water contains pollutants that can pose a health threat, find out if one of 3M’s filters is up for the job!

8. Culligan US-EZ-1 vs. US-EZ-3 vs. US-EZ-4 Filters

Culligan Under Sink Water Filter

Culligan US-EZ-1 Basic Water Filtration System

  •    Estimate: $
  •    Annual Costs: $
  •    Extra Faucet:
Culligan US-EZ-3 Water Filters

Culligan US-EZ-3 Advanced Water Filtration System

  •    Estimate: $
  •    Annual Costs: $
  •    Extra Faucet:
Culligan US-EZ-4 Water Filters

Culligan US-EZ-4 Premium Water Filtration System

  •    Estimate: $
  •    Annual Costs: $$
  •    Extra Faucet:


Culligan provides a carbon-based under counter water purification system with a separate faucet that can be used with 3 interchangeable filtration cartridges: The RC-EZ-1, the RC-EZ-3 and the RC-EZ-4. Where’s the difference?

  • Being highly popular, the RC-EZ-1 is a basic water filter with a maximum capacity of – believe it or not – 3,000 gallons or up to 12 months use. It is NSF Standard 42 certified to reduce chlorine (97.4%), particulates (99.9%) as well as bad taste and odors. In other words, opt for this filter if all you care about is better tasting water and don’t want anything fancy.
  • For higher filtration needs, the RC-EZ-3 removes chlorine and particulates and in addition to that cysts (99.9%), turbidity (98.5%), lead (about 99.0%), atrazine (94.1%) and lindane (98.2%) – all according to NSF Standard 53. Filtration capacity is 500 gallons or 6 months.
  • If you also want to eliminate chloramines (only for tap water), MTBE, mercury, chloroform and dozens of VOCs for increased water safety, the RC-EZ-4 is your best bet. NSF certified against standards 42, 53, 401, & P473. Filtration capacity: 500 gallons or 6 months.

Quick connect fittings and detailed DIY instructions make installing this unit straightforward with no need for calling a plumber. Above that, modular twist on/off filters were designed for convenience and can be replaced in mere minutes and without turning off the feed water supply.

Everything is backed by a 2-year limited manufacturer warranty.


With .5 gallons per minute at 60 psi, water flow is a little low. Also, the included dispenser is made from cheap plastic except for its metal spout, so it’s nothing mind blowing.

Furthermore, the installation kit comes with a 1/2″ water hose adapter. However, if your house has 3/8″ supply lines, it won’t fit. In this case, you will have to make an extra trip to your local hardware store.

Last but not least, for the US-EZ-4 premium filter annual replacement costs are comparatively high.

Our Verdict

Here you get low-cost drinking water filters which are easy to set up and maintain, and effective against lead. Perfect choice for people on a tight budget.

9. Brondell H2O+ Coral UC300 Multi-Stage Unit

Brondell H2O+ Coral UC300 Under Sink Water Filter

Brondell H2O+ Coral UC300

  •    Price: $$
  •    Filter Process: 3 Stage
  •    Annual Costs: $$
  •    Extra Faucet:


The Brondell H2O+ Coral UC 300 is a 3-stage unit that has earned certifications for NSF standards

  • 42 for water aesthetics (chlorine, tastes, odors, particulates and even 98.6% chloramine),
  • 53 for water contaminants with health effects (cysts, mercury, lead, VOCs, TTHMs, …)
  • and 372 for product compliance with lead content.

Above that, a certification for Canadian water filtration standards has been awarded. Altogether, this system gives you access to water of unusual high purity.

Here are some details about its filters:

  • Stage one applies a regular sediment pre-filter, while stage 2 and 3 utilize carbon media.
  • The filtration capacity is 600 gallons of water or 12 months, which is above average and will help you to save in the long run.
  • Water flow is 0.5 gallons per minute, which is okay. You might have to wait a little longer to fill a whole jug, however, remember that thorough filtration requires time.
  • The twist and seal design makes filter changes quick and easy.
  • The chrome faucet even has an integrated LED light that indicates when it’s time to change filters – a handy feature that takes out all the guess work.

Lastly, one year limited warranty got you covered in case something goes wrong.


Basically, the idea is that everything you need to set up this water filter system right away should be included in the package. This way you don’t have to pay a visit to the hardware store, which makes a lot of sense.

However, the 1/2″ to 3/8″ adapters have bad threading and might not tighten onto your cold water supply line properly. So chances are that you will still have to buy a replacement piece nonetheless or otherwise your kitchen will be flooded.

Our Verdict

An under sink water filtration system perfectly suited for tap water treated with chloramine and yet some room for improvement. Once you have everything in place, we are 100% sure that you will be happy with this purchase.

10. Ecosoft 3 Stage Under Sink Water Filter

Ecosoft 3-Stage Undersink Filter System

Cheap Multi-Stage Under Sink Water Filter System: Ecosoft

  •    Price: $
  •    Filter Process: 3 Stage
  •    Annual Costs: $$
  •    Extra Faucet:


The last of our under sink water filter system reviews features the beautiful and sturdy Ecosoft 3 Stage.

The filtration system is available for a fraction of what you pay for other multi-stage units and removes up to 99% of harmful impurities for drinking water that not only tastes great, but also benefits your health.

  • Stage one – A 5-micron polypropylene sediment filter traps dust, sand and other sediments and thereby prolongs the life of the subsequent filters.
  • Stage two – A mix of a carbon/softening filter reduces water hardness and some of the bad stuff that might be lurking in your water, such as chlorine and chlorination by-products, tannins, and a number of heavy metals including lead, iron, manganese and aluminum.
  • Stage three – An activated carbon block removes any residual tastes and odors for a final polish.

Everything is manufactured in good ol’ Germany and partly in the Ukraine. A faucet + installation kit are included in the package and so is a 30-day satisfaction guarantee, a 1-year full and a 5-year limited warranty. Ecosoft’s customer service responds promptly and is super helpful.

Replacement water filters are reasonably priced. Lifespan: 400 gal.


.25 gallons per minute is really not a lot of water, so expect longer waiting times.

On top of that, the installation instructions could be more precise and some of the valves and fittings feel a little cheap. They’ve caused leakages for some users in the past.

Our Verdict

All in all, the Ecosoft 3 stage under sink water filter system combines decent filtration performance with affordability and negligible maintenance cost. We love it!

Under Sink Water Filter Comparison List

Products$Tech/MediaStagesExtra FaucetAnnualUse
Home Master TMAFC-ERP Under-Sink Water Filter$$$RO Water Filtration System7 FiltersYes$$Drinking Water
APEC Essence ROES-50 Under-Sink Water Filter$$RO Water Filtration System5 FiltersYes$$Drinking Water
Olympia OROS-50 Under-Sink Water Filter$RO Water Filtration System5 FiltersYes$$Drinking Water
Woder 10K-Gen3 Under-Sink Water Filter$Charcoal Water Filtration SystemOne FilterNo$Drinking Water
Woder 10K-DC Under-Sink Water Filter$Charcoal Water Filtration SystemOne FilterNo$Drinking Water
CuZn UC-200 Under-Sink Water Filter$Charcoal Water Filtration System3 FiltersNo$Drinking Water
Aquasana AQ-5300 Under-Sink Water Filter$$Charcoal Water Filtration System3 FiltersYes$$$Drinking Water
Aquasana AQ-5300+ Under-Sink Water Filter$$Charcoal Water Filtration System3 FiltersYes$$$Drinking Water
APEC WFS-1000 Under-Sink Water Filter$$Charcoal Water Filtration System3 FiltersYes$Drinking Water
Clearly Filtered Under-Sink Water Filter$$$$Mix3 FiltersNo$$$$Drinking Water
3M Filtrete 3US Under-Sink Water Filters$Charcoal Water FiltersOne FilterNo$$Drinking Water
Culligan Under-Sink Water Filters$-$$Charcoal Water FiltersOne FilterYes$-$$Drinking Water
Brondell H2O+ Coral UC300 Under-Sink Water Filter$$Charcoal Water Filtration System3 FiltersYes$$Water for Drinking & Cooking
Ecosoft 3-Stage Under-Sink Water Filter$Charcoal Water Filtration System3 FiltersYes$$Water for Drinking & Cooking

Other Under Sink Water Filtration System Reviews:

Buying Guide: What You Need to Consider When You Buy an Under Sink Water Filter

You have many, many options when it comes to choosing a water filter system to install under your kitchen counter. In order for you to find a unit that’s suitable for your needs, our buying guide will tell you what to consider:


Almost all water filters do 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 removing certain kinds of contaminants than others. Thus, there are huge 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 tested positive for. What certifications to focus on? Standard 42, 53, 401 and 58 (reverse osmosis filtration systems only).

Filter Technology

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 delivers the best possible results, it might be more efficient for your water conditions to install a filter type that’s much more simple.

Usually, the best approach is to have your water tested as a first step. As soon as you know what you are facing, you can go out and find an appropriate filter.

Filter Stages

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

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 hours 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 filter system was 0.25 gpm.

At the same time, 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 filtered water per minute.

water flow rate

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 single drop of water that 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 greatest 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 single filter cartridge can handle before it needs replacement is relatively high.

One of the filters we reviewed down below has a capacity of 50,000 gallons. If your family uses 3 gallons of filtered water per day, 50,000 gallons 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 an extra 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 over time. 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 Water Filters

Under Sink Water Filtration Systems: 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 can remove 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 an extra 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 tested positive for. 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?
    It should be enough to clean your under sink water filtration system whenever you replace the filter elements. You can clean the filter housings with mild dish soap. Sanitize with bleach if need be – think bacteria.
  • How often should you change an under sink water filter?
    This depends on the capacity of the filter elements. Some last a full 10,000 gallons, others no more than 400.
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Questions about any type of water filter product? Ask away!

And remember: We’ll continue our hunt for the best under sink water filters, adding new under sink water filter reviews to our list occasionally. So come back!

About the Author Gene Fitzgerald

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.
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