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Filtering your drinking water offers many benefits. From better taste to improved safety, there’s actually little reason not to filter. So, the question really becomes what type of filter should be used? A popular choice are under-sink units, which are unobtrusive and easy to install. We’ll help you find the best under sink water filter in the guide below.

Since there are a lot of different models on the market, we spent the time to compile a list of recommendations. We based these decisions on a number of factors, from filtration technology to customer reviews

There are a few things you need to know before buying a new under the sink, so we tried to answer all of the possible questions that a newbie in the under sink market might have.

Conventional Filters

The conventional filters are allowing the filtered water to pass through and come from a separate faucet. It’s connected to your cold water line, although unfiltered water can be used from your original faucet.

One thing that’s complicated on the conventional filters is the installation. Since it requires an additional faucet for the filtered water and fittings to attach the cold water line, they can be difficult to install. They also require an extra hole for the filtered faucet, so if you don’t have one you are going to have to do some drilling.

The bright side of this is that because the filtered water is separated, the longevity of the filter is prolonged.

Here are some of the filters worth mentioning.

Best Value
CuZn UC-200 Under Counter Water Filter - 50K Ultra High Capacity - Made in USA
Runner Up
iSpring US31 Classic 3-Stage Under Sink Water Filtration System for Drinking, Tankless, High Capacity, Sediment + Carbon + Carbon (Newest Version)
Editor's Choice
Home Master TMAFC Artesian Full Contact Reverse Osmosis System, 7-stages, Patented 2-Pass Alkaline Remineralization, Fast 4.5s Fill Rate, 8.5” catalytic carbon, 5-year limited parts
CuZn UC-200 Under Counter Water Filter - 50K Ultra High Capacity - Made in USA
iSpring US31 Classic 3-Stage Under Sink Water Filtration System for Drinking, Tankless, High Capacity, Sediment + Carbon + Carbon (Newest Version)
Home Master TMAFC Artesian Full Contact Reverse Osmosis System, 7-stages, Patented 2-Pass Alkaline Remineralization, Fast 4.5s Fill Rate, 8.5” catalytic carbon, 5-year limited parts
Removes >98% lead, mercury, arsenic
Yes, except arsenic III
Yes, except arsenic III
Yes, except arsenic III
Removes >98% chlorine
Maximum water pressure
No specific requirements
NSF certified media
NSF certified
Best Value
CuZn UC-200 Under Counter Water Filter - 50K Ultra High Capacity - Made in USA
CuZn UC-200 Under Counter Water Filter - 50K Ultra High Capacity - Made in USA
Removes >98% lead, mercury, arsenic
Yes, except arsenic III
Removes >98% chlorine
Maximum water pressure
No specific requirements
NSF certified media
Runner Up
iSpring US31 Classic 3-Stage Under Sink Water Filtration System for Drinking, Tankless, High Capacity, Sediment + Carbon + Carbon (Newest Version)
iSpring US31 Classic 3-Stage Under Sink Water Filtration System for Drinking, Tankless, High Capacity, Sediment + Carbon + Carbon (Newest Version)
Removes >98% lead, mercury, arsenic
Yes, except arsenic III
Removes >98% chlorine
Maximum water pressure
NSF certified
Editor's Choice
Home Master TMAFC Artesian Full Contact Reverse Osmosis System, 7-stages, Patented 2-Pass Alkaline Remineralization, Fast 4.5s Fill Rate, 8.5” catalytic carbon, 5-year limited parts
Home Master TMAFC Artesian Full Contact Reverse Osmosis System, 7-stages, Patented 2-Pass Alkaline Remineralization, Fast 4.5s Fill Rate, 8.5” catalytic carbon, 5-year limited parts
Removes >98% lead, mercury, arsenic
Yes, except arsenic III
Removes >98% chlorine
Maximum water pressure

The CuZn UC 200


CuZn UC-200 Under Counter Water Filter - 50K Ultra High Capacity - Made in USA


  • The UC-200 size can fit in almost all under sink cabinets, so size won’t be a problem
  • The UC-200 longevity can last to 50,000 gallons
  • It removes all contaminants and controls the level of algae and bacteria in your drinking water

The CuZn UC-200 is an under-sink filter that is worth mentioning as one of the best non RO under sink filters.

One of the UC-200 best quality features is the simplicity of installing. Sometimes under-sinks can be complicated and difficult to install, but not the UC-200. The under sink comes packed with a braided stainless steel compression hose. The only thing you have to do is use a crescent wrench to connect it to the cold water line. It can’t get any simpler than that!

The manufacturer also says that you can connect it to the hot water hose as well. The quality of the hot water will be improved but slightly less than the cold water.

You have to be careful about the dimensions, make sure that the CuZn UC-200 can fit in your cabinet. The UC-200 is 4.5 x 4.5 x 15 so keep those dimensions in mind when you decide to purchase it.

The filter of the UC-200 consists of 3 different layers of filtration media.

The first filter is a micron sediment membrane. This takes care of all the larger sediments like plastic fibers, rust, and sand.

The second filter is located inside the membranes and is acid-washed coconut shell activated carbon. This targets all the chemicals like pesticides, chlorine, chloramine, and also keeps the taste and odor normal.

And finally, the third filter is a layer of KDF 55. This filter is used to control scale, algae, and bacteria. It removes inorganic contaminants like heavy metals (lead and mercury). This filter is an NSF certified medium.

Unlike the iSpring, the UC-200 allows healthy minerals like calcium and magnesium to go through. This feature helps water to smell and taste better.

The longevity of the CuZn filter can last up to 50,000 gallons of water. This means that you can have peace of mind about replacing any part of the filter in the next 5 years.

The CuZn allows you to see through due to its clear housing, so if you are ever concerned about the water quality, you can just have a peek and check on the sediment filter to see if it’s overloaded.


  • 5000-gallon filter life
  • Good flow rate
  • Very simple installation 
  • The test showed that the filter removes all of the chlorine


  • The filter is large and very heavy
  • Doesn’t reduce TDS level

The iSpring US31 Under Sink



  • Uses a 3 filter system when removing a wide range of contaminants 
  • The remineralization process keeps the sodium, calcium, and other useful minerals in your water

This under sink filter is one of the simplest and most effective under sinks in today’s market. Equipped with 3 filters that target different types of contaminants, keeping the water without odor and a nice taste.

The iSpring US31 filter is very simple to install. The manufacturer, iSpring provides you with all you need and more. The size of the filter is just right to fit in most home cabinets, which makes it a lot more attractive and makes it one less thing to worry about. The longevity of the filters depends on the usage, but it can be used without replacing it for a year.

The reports showed that the US31 does its job, the contaminants in the water were lessened, but the minerals like calcium, magnesium, sodium were not affected. Also, the water pressure does not drop, which can be a problem on other under sink filters.

We can say that the US31 is an amazing under-sink for its low price.


  • Testing proved the filter effectively removes the contaminants while preserving the  magnesium and calcium
  • The price is reasonable
  • The size is perfect for small cabinets
  • The installation is very simple


  • There might be dripping from the second faucet
  • Some users did report a slightly bigger drop in the water pressure

Home Master TMAFC


Home Master TMAFC Artesian Full Contact Undersink Reverse Osmosis Water Filter System,White


  • Removes up to 98 % of all the harmful contaminants in the water
  • It can produce a staggering 2000 gallons per year
  • The TMAFC uses a 7 stage filtration system to purify the water

The Home Master TMAFC is a close contender for the best under sink water filter. The only reason it’s not our #1 pick is that it’s a bit pricey – but for a lot of folks, the higher price tag is worth it. This is an advanced product with a 7-stage filtration system. It removes up to 98% of chlorine, chloramine, and other contaminants from your water supply.

Another unique feature of this filter is that it actually adds back in healthy minerals like magnesium and calcium. Many filters strip these minerals out of your water, and adding them back in is healthy and can improve the taste of your water. It also features a fast-flow filter that is up to 2x as fast as many traditional reverse osmosis filters.

The kit comes with everything you need (including a faucet), and the filters are designed to last about a year/2,000 gallons


  • You don’t need a professional to install it
  • It has a 5-year warranty
  • The filter can last up to 2000 gallons produced
  • Testings showed the excellent work of the filter


  • The valve is very small
  • The price is a little high

The Culligan US-600A Filtration System


Culligan US-600A Under-Sink Drinking Water Filtration System with Filter, 1,000 Gallon, White


  • The Culligan doesn’t require an additional faucet 
  • Removes a wide range of contaminants from your drinking water
  • The Culligan can produce 2.5 gallons per minutes 

The US-600A is a simple under sink filtration system that uses a three-stage filtration to produce pure quality drinking water. It has an NSF certification, so you know it is a system you can trust.

The capacity of water it produces is six thousand gallons and offers a two and a half gallon flow of clean purified water per minute. The installation is simple, it does not require drilling or additional faucets, you can use your faucet for this type of system.

Because the filter uses your existing cold water faucet, it may be a change in the water flow. Filters tend to make the water flow slower, although most of the users of this system said that that change was quite insignificant.

According to the manufacturer, this simple filtration system removes a wide range of harmful contaminants from your water, like chlorine, benzene, heavy metals, lead, bacteria, and more. 


  • Simple installation
  • It has NSF certifications
  • Removes contaminants effectively 


  • Makes the water flow slower

Clearly Filtered 3-Stage Kitchen Filter


Clearly Filtered 3-Stage Under-the-Sink Replacement Filter: Removes up to 99.9% of Fluoride, 99.9% Lead, and 99.9% of Mercury and many more Tap Water Contaminants


  • Includes 3 filter system
  • Removes 99% of all contaminants from the water
  • Stainless steel high-quality water lines

The CF 3-Stage Kitchen Filter does its job at the highest level, producing as close as to 100% pure drinking water due to its Affinity Filtration Technology.

The Affinity Filtration Technology uses multiple stages of filtration to ensure that the drinking water is 99.7% free of more than 200+ contaminants.

The first stage of the filtration process is removing the chlorine and VOCs, while improving the water’s taste by removing the fog and odors, making it clear and smell free. Stage two of the process includes cleaning the water from 99.9 % of all heavy metals, pesticides, herbicides, lead, radiation, PFAS, arsenic, and chromium. The final stage removes the fluoride, while most under sink filters don’t address the issue of fluoride, the 3-Stage kitchen filter removes it from your drinking water.

The design of the CF 3-Stage Filter System is a compact and slim filter that takes up little cabinet space, this will solve the issue if your under-sink cabinet is small.

The longevity of the filters is also impressive, they need replacing after 2000 gallons, which means u don’t have to do a thing in the next 1 to 2 years, depending on your usage. Also, the replacement couldn’t be easier, all you have to do is unscrew the old one and screw in the new one, and you are done.

One issue we encountered on the CF 3-Stage Filter system is the lowered water flow rate. It doesn’t lower it significantly, but nevertheless, it’s a downside to the filter. The price is a bit higher than other filters of this kind, but considering the quality of the 3-Stage filter, it might be worth it. On top of the price, the manufacturer guarantees a lifetime warranty on the system, with a 30-day money-back offer and free shipping included!


  • The taste and odor of the water improved by a lot
  • The installation is very simple and can take 15 minutes


  • There’s a drop in the water flow rate

Pentair Pelican 3-Stage Under Sink Filtration System



  • Can produce 1500 gallons of purified water
  • Uses a 3 stage filtering system
  • Keeps the water pressure from 40 to 80 PSI

If you are looking for a simple under sink filtration system that produces high-quality pure water, and requires no maintenance or doesn’t waste water, that the Pelican 3-Stage Drinking filter might be the right choice.

The Pelican 3-Stage offers up to 1500 gallons of clean, filtered water. With its three stages of filtration ensures that your water tastes great and is odor-free. The Pelican 3-Stage also removes all of the contaminants from your drinking water, like chlorine, bacteria, chloramine, lead, and many more.

The Pelican’s 3 stages also include a 25 Micron Pre-filter and two Catalytic GAC Carbon filters that help in removing the chlorine and chloramine, while keeping the healthy minerals like magnesium and calcium. The system produces 1500 gallons of water while maintaining a 40-80 PSI water pressure, this is very effective for smaller households.

It’s interesting that Pelican’s goal is environmental sustainability, meaning the filter uses fewer resources through the manufacturing process than its competitors.

The design of the Pelican is sleek and stylish, it comes with an option of 3 faucets, one in chrome, brushed nickel, and one in bronze. The dimensions are 12.5” wide 15” in height and 4.5” in diameter.

The installation is simple if you are looking at the user guide, it’s proven very effective. The maintenance is easier, all you have to do is remove the cover and replace the cartridge once a year, depending on usage of course. 

The manufacturer offers a one-year warranty on all parts.

One of the things we didn’t like about the Pelican is that it didn’t have any certifications listed.


  • Water pressure isn’t reduced
  • Good design on the faucet
  • The 3 stage filtering system is proven very effective
  • Eliminates taste and odor


  • Does not have any certifications listed
  • The dimensions may be an issue if you own a small cabinet




  • Removes 99% of all the contaminants in the water
  • APEC uses high-quality components, without leaks and high durability

The APEC ROES-50 is the best under sink water filter available today. This is a reverse osmosis filter, which is an advanced filtration tech that efficiently filters out over 1,000 unique contaminants. The technology is able to remove 99% of all contaminants in your water.

This product is also a best-seller on Amazon and consistently earns excellent rankings in under sink water filter reviews. It’s well made, durable, and leak-free, although it does require some basic plumbing knowledge to install. We ranked it as the best reverse osmosis water filter, as well as the best under-sink unit.

The APEC ROES-50 also comes with a 2-year limited warranty, so it’s covered in case of any issues. It’s a complete kit with everything you need to get started


  • 2-year warranty
  • Testing showed the efficiency of the system
  • Quality parts included


  • The installation is a bit more difficult than other systems

The Basics Of The Reverse Osmosis (RO) Type Water Filters

The Reverse Osmosis system filters your water by taking away all the contaminants in your water supply, due to the multi-stage filtering process along with the tank system. The tank system contains a raisin that lets clean water go through and it absorbs the harmful contaminants.

One of the great things about the RO systems is that it usually comes with a faucet that acts like a Conventional Filter. This will save you some money on filter replacements and gets you the most of the under sink water system.

These types of systems are highly regarded and proven to be the most effective under sink filtration systems due to the ability to use reverse osmosis.

These RO systems are a little more costly than the regular filtering system, but you are getting the highest quality filtered water, and you can’t put a price tag on that.

The installation on the RO system is a bit more complicated than on the regular one since there are a few more moving parts, but the manufacturers are making each new model a bit easier to install than the previous one.

One of the things we don’t like about the RO system is the need to produce wastewater after the filtration. This wastewater is any water that is not let through. This wastewater needs to drain and by some people, this is considered a waste of water.

How The Reverse Osmosis Filtration System Works

The RO system offers an extensive filtering process that’s designed to eliminate all of the harmful contaminants from the water. 

The filtration process starts by removing the sediment from your water, which includes large particles like rust and sand.

 Then it continues by removing the carbon, chemicals such as chlorine can damage the filter membrane if they are not removed in this stage of the filtering process.

 After the carbon removal, the Reverse Osmosis takes place, this stage of the process removes all particles that are larger than the water molecule, and it’s where most of the purification takes place. 

Next is the remineralization, some RO systems will remineralize the water with minerals that are good for the body like calcium and magnesium in order to balance the pH levels of the water. This also improves the taste of the water.

The final stage of the filtering process is the second carbon stage, or commonly referred to as polishing. Its function is to remove any odors or taste that the previous filters missed.

With all that being said, here are some of the best RO systems currently on the market.

The APEC Top Tier Alkaline Mineral Ultra Safe Reverse Osmosis



  • Uses a 6 stage filtration system that removes all contaminants while keeping the water without taste and odor
  • The faucet has a great elegant design
  • Its size makes it possible to fit in any under-sink cabinet

The size of the filer is a thing all buyers need to consider before deciding on an under sink filter. The manufacturers of the APEC made sure that it can fit in most cabinets. If you are having an issue with overcrowded cabinets and the space for a new filter is limited, the APEC might be the right choice for you. It provides one of the best filtration systems in its price range while taking the least minimum space.

The APEC comes with 6 unique stages of filtration, and an efficient Reverse Osmosis tank. The filters on the APEC tested very well when it comes to removing contaminants that are most commonly found in our water. Also, the taste, odor, and the fog in the water are immediately improved thanks to its carbon block filters. Besides the 2 carbon block filters, the APEC has additional filters that eliminate sediment, lead, and many other heavy metals frequently found in our water.

The APEC comes with an included chrome finished faucet, making it look elegant. The faucet can swivel for 360- degrees. Making it far better than many other faucets on the market. The faucet also provides a great water flow rate.

The parts of the APEC have a long lifespan and can be easy to change. The manufacturer also provides a 2-year warranty on all the components on the filter.

The APEC comes with an included chrome finished faucet, making it look elegant. The faucet can swivel for 360- degrees. Making it far better than many other faucets on the market.


  • 2-year warranty is included
  • The design of the faucet is great
  • Water testing proved the efficiency of the system


  • The valve is made of plastic and it can easily break

Express Water Reverse Osmosis Water Filtration System RO5DX


Express Water RO5DX Reverse Osmosis Filtration NSF Certified 5 Stage RO System with Faucet and Tank – Under Sink Water Plus 4 Replacement Filters – 50 GPD, 14 x 15 x 5


  • It can produce up to 50 gallons of water a day, more than enough for most families
  • Color coding on the filter makes it very easy for maintenance of the system

The RO5DX under sink filter is equipped with five different filters, each one has a dedicated job of making your water better. Since there are five filters, they can be easily confused when removing, so the manufacturer made this as easy as possible, by making the filters color-coded and labeled.

Each filter has a different color, so you don’t mix them up, because if you do the filtering performance will have some difficulties.

Along with the five filter system comes a brushed nickel faucet that looks very luxurious and modern. 

With the combination of the five filter system and the Reverse Osmosis, the quality of the water is guaranteed. The RO system has some safety filters built in to avoid leaks, also the RO tank stand ensures that the tank will stand upright, this helps avoid massive leaks. 

The design of the tank is sleek and spacy, therefore not taking up a lot of your cabinet space under the sink. The tank can produce 50 gallons of water a day, that’s very impressive since a family of four needs around 4 gallons a day to stay hydrated.

Another great feature is the shut-off valve that comes included in the price. The valve can detect a leak or excess water in the system and it shuts it down. Great way to avoid flooding your kitchen.

The filters on the system are long-lasting and can be removed easily just by pressing a release button. The manufacturer also gives a 1-year guarantee on all parts of the system.

Although, one of the cons we noticed on the RO5DX system was the water flow rate. The rate is 0.8 GPM, and that’s one of the lowest on filter systems in this price range.


  • It has 5 different filters
  • The maintenance is made easy with the color-coding
  • The system can produce 50 gallons a day


  • The flow rate is slower
  • Expensive replacement on the filters

The iSpring RCC&AK 6 Stage Reverse Osmosis under sink


iSpring RCC7AK 6-Stage Superb Taste High Capacity Under Sink Reverse Osmosis Drinking Water Filter System with Alkaline Remineralization-Natural pH, White


  • Works perfectly in reducing the pH level on the water
  • Uses a remineralization process to keep the healthy minerals in the water
  • It uses color-coded parts to make the maintenance easier

The RCC&AK system proved to be one of the best filtering systems on the market. The testing of the system showed that the pH level of the water has increased dramatically. This is because the system offers a ton of filtering levels, and removes a wide variety of contaminants frequently found in our water. The system has a 6th stage filtering process, where the alkaline remineralization process takes place. During this remineralization, the minerals that are healthy for the body are restored in the water, and the pH level is more balanced.

The system is equipped with more than one water tube, so just like RO5DX, the iSpring manufacturers made a color-coded tubing that allows you to install the filter easily, and when the time comes changing the filters. This also ensures that when installing the system you won’t make any mistakes that can lead to leaks.

The size of the RO is made to fit in any cabinet, and it can provide more than a ton of water a day. That’s more than enough for any family.

Along with the filter comes a brushed nickel faucet that has a sleek and modern design. It looks like it’s high quality, so leaks might not happen from this faucet.

There’s a big difference in the taste of the water in alkaline systems compared to the non-alkaline system. You can definitely notice the difference in this case.

The only thing that we didn’t like about this iSpring system is that it produces 2 gallons of wastewater for every 1 gallon of filtered water. That might be a thing you need to consider when shopping for a new under sink filter.


  • Produces 75 gallons a day
  • Size of the tank can fit in any cabinet
  • Installation is simple and helped with DIY videos


  • Produces a lot of wastewater
  • The flow rate is slower than expected

The iSpring RCC7AK


iSpring RCC7AK 6-Stage Superb Taste High Capacity Under Sink Reverse Osmosis Drinking Water Filter System with Alkaline Remineralization-Natural pH, White


  • The RCC7AK removes 99 % of all the contaminants in the water

  • The RO membrane has a 0.0001-micron pre-filter taking the purifying to the highest level of quality
  • It uses polypropylene pre-filters to keep the sedimentation from reaching the membrane


The Ispring RCC7AK is a high valued under sink filter that comes with a multiple-stage filtration and a remineralization system. Those two features helped the RCC7AK to win the WQA Gold Seal.

Also, it’s certified against all NSF/ANSI standards, which means that the pureness of the drinking water is guaranteed.

The filter removes 99 % of all pollutants like chlorine, arsenic, fluoride, asbestos, viruses, bacteria, and hormones. The filter also removes 98% of all the lead in the water.

The iSpring RCC7AK has 3 pre-filters: a carbon block, granular carbon core, and three fine sediment mesh. This is what makes the quality water purification possible.

Besides the pre-filters, the water also passes through the RO membrane with small pores (0.0001 microns). All of this purifying makes the water drinkable.

After the RO membrane, the water is purified by a post-carbon filter before going to your faucet. The only issue we noticed is that the filters clean out all the heavy toxic metals, but it also filters out a lot of minerals that are important for the human body, so this might make the water taste a little acidic.

Another great thing about the RCC7AK is the quality of the parts. The filtration system can last up to one year. Since the water passes through the 3 stages of pre-filtration and is already very clean, the RO membrane can even last up to 3 years. You can change it sooner if you think the water quality is not good enough. The polypropylene pre-filters allow you to see the sediments so when you see all the sediments built-up, you should think about changing it.


  • The installation is very easy
  • Testings showed a better taste of the water
  • Good pH level


  • The price might be too expensive

The Brodell Circle Under Sink RO model


Brondell Circle Reverse Osmosis System, Under Sink, Black – 4 Stage RO Water Designer Chrome Faucet– Quick Change Filter, WQA Gold Seal-Certified


  • Provides great speed in refiling the tank, while producing a low amount of wastewater
  • It uses Led indicators to remind you when it’s time to change its filters
  • The filtering process removes all of the harmful contaminants and bacteria


The Brondell Circle RO model is one of the most interesting RO systems in the current market. The innovative design makes the Brondell a great contender in the race for the best under the sink. Instead of the traditional RO approach, the Brondell comes with a large tank and set of filters, and everything you need is encapsulated within the black box design. The size of the box isn’t particularly the smallest under-sink model, but it still can fit easily in most under sink cabinets.

The Brondell Reverse Osmosis system has a 6-liter tank and the water goes through four filtering processes. The water testing done on this system showed a lower TDS (total dissolved solids) that’s better than most under-sink systems.

Along with the sleek black box tank comes a chromed tap and a faucet, that might fit in great in any kitchen, due to its simple chrome design.

Another great thing about the Brodell circle RO system is the speed to refill the tank, it was by far one of the fastest in the RO systems category. Also, the amount of wastewater that the tank produces is significantly less than other RO systems. 

This RO membrane has an automated filter that cleans and flushed all water, this will help the longevity of the other filters. This will give you some peace of mind since the filters can even last up to 2 years.

The filters on the Brodell have a LED change indicator that tells you when the filter needs to be changed. Although the price of the new filters is a little more expensive than other models we encountered.

Due to its four filtering processes, the quality of the water is on the highest level, along with all the harmful pollutants like fluoride, arsenic, and bacteria, the filter also removes all of the total dissolved solids.

Besides the things we like about the Brodell, there are some things that might raise concern. One of those things is the time the Brodell takes to regenerate the water. During this time you won’t be able to drink clean water through the filters.


  • TDS levels were very low on the testing
  • The size of the tank is smaller than usual
  • The design is very luxurious 


  • The cost of replacing a filter is expensive
  • The price of the RO system is also quite expensive

Aquasana OptimH2O Reverse Osmosis



  • OptinH20 operates with a pressure range of 40 to 100 PSI, more than most filters in this category
  • It uses a remineralization system to keep useful minerals like calcium and magnesium
  • It can produce up to 13.32 gallons a day

The OptimH20 provides you with the purest drinking water possible. Coming from a highly regarded under sink filter company Aquasana, the OptimH20 might be the right option to remove all the harmful contaminants from the water.

The first of its kind, the Optim H20 combines the Reverse Osmosis system plus the Claryum under the sink, ensures that the quality of the water is at its highest level. The filtration technology and the Reverse Osmosis system can efficiently remove more than 90 other contaminants from the water. The OptimH20 can remove up to five times more than any other Reverse Osmosis system.

The filtration process of the Optim is a six-level filtration that includes the Reverse Osmosis, activated carbon, ion exchange, sub-micron filtration, catalytic carbon, and remineralization. This process removes contaminants like lead, mercury, chlorine, pesticides, herbicides, but it keeps the healthy minerals like magnesium, calcium, potassium in your drinking water thanks to the remineralization process.

Along with the OptimH20 filter comes a brushed nickel faucet, a Reverse Osmosis tank, three filters, and all the other parts you need for installation. Most of the customers said that the installation was fairly easy because Aquasana provides all the videos that can teach you how to install it error-free. Also, the maintenance of the filter is simple and easy.

The OptimH20 comes with a two-year warranty, and the parts of the systems can last up to 1 year without any problems. The OptimH20 can produce 13.32 gallons of water a day, that’s more than a regular family of four needs. It also operates with a pressure range between 40-100 PSI.

The few things we didn’t like about the OptimH2O is the water seems a little slower than regular, and the included tank does not have an automatic shut off button.


  • The filter life is 600 gallons
  • The carbon filter is very effective in removing the taste
  • The installation is simple


  • The Flow rate is slower than usual

The Waterdrop WD-G3-W Filtration System


The interesting thing about the Waterdrop WD-G3-W is that it is a tankless system. Most of the Reverse Osmosis systems use a tank and that can cause some problems if you don’t have enough cabinet space.

The WD-G3-W purifies the water quickly, that way eliminating the need for a holding tank for purified water. The tankless design also makes the installation easier, since you can do it yourself and there’s no reason to hire a professional.

This Waterdrop unit features a monitoring panel that alerts the consumer when the filter is in need of replacing or is faulty. Most of the traditional RO systems do not have an indication system.

Another thing that makes the Waterdrop unit better than its competitors is the capacity of water it can purify. The traditional RO systems can treat about 50 gallons per day, but the WD-G3-W can purify up to 400 gallons per day and that’s an impressive number.

Overall we can say that the Waterdrop WD-G3-W is an excellent example that sometimes different is better. It delivers water faster, produces more, takes up a lot less space, has multiple NSF certifications, and its price is similar to its competitors.


  • Produces 50 gallons per day
  • Easy installation 
  • Monitoring panel


  • The flow rate of the water is slower than expected
  • Price a little higher than the competitors

Conclusion on the Reverse Osmosis System

The Reverse Osmosis is a complex system with a big reputation for producing great tasting and pure drinking water. The Reverse Osmosis system uses water pressure to push the water molecules through the fine membrane that removes all of the harmful contaminants.

The RO system membrane is used to separate the pure drinking water from the contaminated one. The water that’s contaminated is forced down the drain into the contaminated side of the filter system. Most of the RO systems have a carbon filter, a membrane, a storage tank, and a sediment filter.

All of these parts and features help in producing the purest water a home can have.

With all that being said, the RO system has some issues that can change your mind. One of the issues that might get you thinking if this type of system is the right for you is its price, the RO filter system can be a little pricey compared to other water filtering systems on the market. The other thing that might be an issue is its size, the RO system takes some space from your cabinet. Although some RO systems are smaller and can fit with ease. Another thing that is more complicated on the RO system is it’s installation, these kinds of systems contain more parts, making it more difficult to install without proper knowledge or help.

How Does An Under Sink Work

Under-sink filters can be separated into two groups, regarding it’s working ways. The simplest method of working is where the water filter system is directly in the path where the cold water makes its way to the faucet. This way the filter system is treating all the water going into the faucet. You could say the filter system looks like a whole house water filter. The other working method has a separate feed of cold running water that it treats and sends to the sink but through a second faucet or a spigot.

The benefit of the first working method is that it’s treating all running water going through the main faucet, and has a larger water flow. But, when you consider a faster water flow rate isn’t the right thing you need, since the water isn’t spending much in the filter to be filtered from all the harmful contaminants. The second method design is only treating a part of the water supply that’s only being used from the special faucet or spigot. As a result, the water has more time to spend in the filtering system.

Why Should You Install an Under Sink Filtering System

The main reason for that question is improving the quality of your drinking water. All you have to do is ask yourself “is my tap water pure? “, or “is my tap water healthy?”, maybe “does my tap water contain the healthy minerals water should contain?”, if the answer to one of those questions is no, then you have your reason.

Under Sink filtering systems have improved a lot since its beginnings. You can buy a new affordable state of the art Under Sink filtering system for a reasonably low price on the market.

Now you can afford to remove hundreds of contaminants from your drinking water thanks to a little filter just under your sink. Besides the price, the manufacturers have made the installation easy as it goes. Thanks to their user manuals, videos, and just the simplicity of the filtering system, you can save hundreds of dollars just by installing it yourself.

Another great thing is the mobility of the filtering systems, even if you decide to move or just simply transfer the filtering system to another faucet, you could simply remove it with ease and install it to your new desired location.

How to Choose The Right Under Sink For Your Household

When you are out shopping for an Under Sink filtration system there are a few important factors you need to consider, and maybe this will help make your decision easier.

The Size and Capacity

This might be the most important thing you should consider before purchasing an Under Sink. Lots of people forget to check and take measures of their cabinet size so they end up buying an Under Sink that does not fit. To avoid this headache consider this before anything else.

There are options for people that don’t have a lot of free space in their cabinet under the sink, like the simple and conventional filtering systems, but if you do have a lot of free space you might consider a Reverse Osmosis system.

The simple filtering systems don’t require a lot of space since they are connected to the cold water line and use the one faucet. This is a simple and working way if you are limited in space and want to keep things simple. They are also cheaper than other systems.

On the other hand, if you have a lot of free space and you can afford a more expensive solution the Reverse Osmosis systems can offer you a lot more in terms of filtering water.

The Reverse Osmosis system provides you with drinking water of the highest quality, they use 5 or more filters that make sure every contaminant is removed.

They use a tank so they can accommodate over 50 gallons of water every day, more than enough for a family’s daily use. You will not have unlimited access to water due to its working system, but the purified water will be rid of more than 100+ contaminants.

The Flow Rate

The flow rate on the filtering system is a big concern for some users and we can’t blame them. It’s proven that most of the filtering systems do lower the water flow rate, although some do insignificantly it still may cause some concern.

The reason why the flow rate loses its speed is that the water is going through multiple levels of filtration, like carbon, stone, chemicals, heavy metals, and many more.

Flow rate is measured in GPM (Gallons Per Minute), this can vary from 0.8 to 2 GPM depending on the filter. Another thing that factors the flow rate is the PSI on your water supply. The PSI is something you can’t control and it depends on your water provider, but it affects the water flow to a great extent.

Although this is a concern, the manufacturers are aware of this and are working to improve the flow rate on their filtering systems.

Filtering Size

Keep this in mind as the most important issue when deciding. The size of the Microns can impact the filtering process and its outcome. Sometimes the size of the Microns can sneak through the filters and still be in your glass, so to avoid that you should consider a filter that prevents Microns of all sizes from sneaking through.

Contaminants in the water are very small that we cannot see with the naked eye, so when buying a filter look for filters with the smaller size of its Micron filtering.

Installation and Maintenance

To many users maintenance can be an issue, and we can’t blame them. When making the decision consider the longevity and warranty of any parts of the filtering system.

On most filtering systems removing or changing a filter or a part can be easy, that’s because the manufacturers made it very easy. Most of the filters have a release button, and you can oversee their condition. By doing this you will know when it’s time for a replacement.

The installation can also cause some difficulties, but it will completely depend on the filtering system you choose. Every system is different, so some may take longer to install then others, but if you follow the users’ guidebook you can do it in a short time, without any difficulties.

For example, if you decide to get a Reverse Osmosis system, it has more parts and more hoses to bring water into the tank. You will find this more difficult than other simple filtering systems.

Luckily for us, the companies made sure that their products are as easy to install as they can be, providing the users with manuals and videos of the installation.

How to Install Your New Under Sink Water Filter

Installing an under-sink water filter is relatively simple for folks who have basic plumbing knowledge. If you’ve never done any basic plumbing work, you may want to hire it out.

Before you get started with the install, keep a few things in mind. You’ll want to measure the area under your sink, to make sure that the filter setup you’re considering will actually fit. Next, you’ll want to check the instructions included in your manual and make sure you have all the necessary components and tools for the installation. 

Most filters will come with specific components you need, and may even come with mounting hardware – but it definitely varies depending on which product you go with.

Once you’re ready to install, check the manual from the manufacturer for instructions. For an overview, this video does a good job of explaining the basic installation process.

The Importance of Water Filters

Taste Filtered water typically tastes significantly better than unfiltered tap water. Tap water can take on a variety of unpleasant flavors – but it may not be noticeable until you try something better! Good filters can reduce the taste of chlorine and other chemicals, as well as metals and minerals that could be contaminating the taste of your water.

SafetyDepending on where you live, how old your pipes are, etc. your water could contain any number of potentially harmful contaminants. Even things that are added to water almost everywhere, such as chlorine, can cause harm and are linked to an increased risk of cancer.

Peace of Mind – Nothing beats knowing that you’re drinking clean, pure, and safe water. That peace of mind is priceless – and it may actually inspire you to drink more water!

How We Chose 

Filter Technology – There are lots of different styles of water filtration. We focused on effective technologies, namely reverse osmosis and multi-stage filters that use a mix of methods.

Value – To get a good deal for your readers, we focused on models that offered great value for money. That doesn’t mean cheap products – but rather, products that are well worth their price tag and last a long time.

Reviews – We rounded out our own research and testing with a close look at lots of under sink water filter reviews from customers. This gave us a wider perspective on each product.

Durability – Even the more affordable units are $100+, so you definitely want them to last! We considered the build quality of each unit, as well as the expected lifespan of the filters.

Frequently Asked Questions

What is Water Filtration?

Water filtration is a process that purifies the water by removing all of the harmful contaminants.

Do these filtration systems reduce lead?

Yes, the majority of today’s filtration systems reduce the amount of lead in your drinking water.

If I have a water softener do I need a water filtration system as well?

There’s a big difference between a water softener and a water filtration system. The water softeners job is to remove the calcium and magnesium from your hard water with intention of softening it. The calcium and magnesium are replaced with sodium. On the other hand, the water filtration systems job is to remove all harmful contaminants from the water.

What is Micron Rating?

Micron rating is the measurement of a unit that’s called a micron. The micron is equal to one-thousandth of a millimeter. Micron ratings are used in water filtration systems to measure the size of its particulates, such as sediment, sand, silt, and others. Filters with a higher micron rating remove larger particles, while the ones with a lower micron rating remove the smaller particles.

How can I know what’s in my water?

You could ask for a drinking quality report if you are a user of municipal drinking water. You could also test the water yourself by doing various tests.

What is sediment filtration?

Sediment filtration removes particulates such as rust, sand, silt, and dirt from your drinking water. The best solution for sediment filtration is a point of entry system of filtration. This way the sediment doesn’t get into your home and doesn’t damage the plumbing. Consumers that are using well water are more prone to having high levels of sedimentation in their drinking water.

Do all water filtration systems have two faucets? 

If you are using a Reverse Osmosis filtration system you are going to need an extra faucet for the filtered water. There are also simple systems that connect to your cold drinking water and filter the water coming only through the main faucet, so there’s no reason for installing another one.


With everything being said, we can conclude that an under sink filter system can be beneficial to you and your family’s health. They are a cheap and effective alternative to the whole-home water filtration systems and require much less maintenance. So if you can’t decide if you need a water filtration system or perhaps which one to buy, we hope that you found this review helpful in making the decision easier.