The 10 Best Under Sink Water Filters: Reviews & Ultimate Guide

This is our review of the best Under Sink Water Filters of 2023.

We reviewed several under sink water filters and found out that the Waterdrop G3 Reverse Osmosis Under Sink Water Filter System is the best one.

We know that it isn’t easy to select an under sink water filter, as you need to understand the different types, the main factors to consider when buying, the pros and cons of each model, and so on.

To make this task easier for you, we combined our expertise on the topic plus some extensive research, to put together a comprehensive under sink water filter guide and a review of the best models available in the market, for different situations.

In this article, you will find out the best under sink water filters available, their pros and cons, an explanation of why they are better for specific situations, and a detailed buying guide to provide you all the relevant information to choose the best under sink water filter for you.

Let’s get started!

Our Top Picks for Best Under Sink Water Filters

• Waterdrop G3 Reverse Osmosis Under Sink Water Filter System (Best Overall RO Under Sink Water Filter)
• Aquasana AQ-5300 3-Stage Under Sink Water Filter System (Best Overall Conventional Under Sink Water Filter)
• CuZn UC-200 Under Counter Water Filter (Best Overall Simple Under Sink Water Filter)
• iSpring RCC7AK 6-Stage Under Sink Filtration System (Best Value RO Under Sink Water Filter)
• APEC WFS-1000 3 Stage Under Sink Water Filter (Best Value Conventional Under Sink Water Filter)
• Frizzlife Under Sink Water Filter System (Best Value Simple Under Sink Water Filter)
• APEC Water Systems ROES-PH75 Reverse Osmosis Under Sink Water Filter (Good Choice RO Under Sink Water Filter)
• iSpring CU-A4 4-stage Under Sink Water Filter (Good Choice Conventional Under Sink Water Filter)
• Waterdrop 15UA Under Sink Water Filter System (Good Choice RO Simple Under Sink Water Filter)
• Filtrete Advanced Under Sink Water Filtration System (Best Budget Simple Under Sink Water Filter)

10 Best Undersink Water Filters Reviewed

After investing our time researching and reviewing several undersink water filters, we identified the 10 best options for different purposes.

Buying Guide for Undersink Water Filter

Before buying an under sink water filter you should get a clear idea of the important topics regarding this type of purchase, like the main factors to consider, the pros and cons, and how you can install it, and the most frequently asked questions about under sink water filters.

That being said, we put together a comprehensive guide that covers these important topics.

What to Consider When Choosing the Best Under Sink Water Filter

When researching for an Under Sink Water Filter to buy, these are the key features that you should consider:

Type

The type of under sink water filter you choose will have an impact on its cost and difficulty of installation.

The most simple under sink water filters are easy to install, as you don’t need to add an additional faucet to your kitchen sink.

The conventional or regular under sink water filters will require an installation of a specific faucet that will come with the package. This will make the installation more complicated, but you will have filtered water that will flow directly to this new faucet, leaving the other as is. 

Then, there is a special type of under sink water filter, the Reverse Osmosis water filtration system, which is like a conventional under sink water filter regarding installation but combines different filtration stages to deal with several types of contaminants.

Contaminants to Remove

First, you should know which contaminants you need to deal with. You can do this, by checking the CCR of your water provider or by checking the water of your home by yourself, using a water test kit.

Then, with this information in mind, you can check which filters can reduce or eliminate the contaminants in your water. If your water is highly contaminated, you might need a more powerful filter like a Reverse Osmosis filtration system.

Size

You should check the dimensions of the under-the-sink water filter before you buy it, to make sure it fits under your counter. 

Some models are larger than others, and if you go for a RO system it might have a tank, which will need additional space.

Costs: Initial and Maintenance

You should consider the costs associated with buying an under sink water filter before you buy it, to make sure you make the right choice.

Take into consideration not only the initial cost but also the associated costs related to replacing the filters, which you will need to do once or twice a year, depending on the filters.

Certifications

Both NSF or WQA are independent third-party accredited institutions that certify water filters to ensure that they can remove certain harmful contaminants. 

While some brands mention that their products remove specific contaminants, you can only be sure about the products with these certifications, because they were tested by third-party accredited institutions.

Flow Rate

With an under-sink filter, the water needs to go through some filters which will slow down the purified water that will flow from the faucet, which is named the flow rate and it is typically measured in gallons per minute (GPM).

A low flow rate will mean that it can take some time for you to fill a glass of water or a pot of water to cook, which can be problematic if you need lots of filtered water.

Ease of Installation

A regular under sink filter comes with a separate faucet for the filtered water, and if your counter is not already prepared with a pre-drilled hole for an additional faucet, you will need to drill through it, making the installation more difficult.

Read the installation instructions of the undersink filter that you choose to check if it is something that you can do by yourself. Depending on your ability to DIY tasks, you may need external help to install an under sink water filter, so consider this cost into your budget.

Filter Longevity & Capacity

You will need to replace the filter cartridge of your under sink water filter with some frequency, and the longevity of your filter is directly linked to its capacity and the amounts of contaminants in the water.

If your water is highly contaminated, it’s normal that the filter will last less time as it will be more used than normal.

If you select a RO system you need to replace different filters, with distinct frequencies. Usually, the semi-permeable membrane needs to be replaced every 2 years, while the other filters should be replaced once a year.

Waste Water Ratio

This factor is only important if you are looking to buy a Reverse Osmosis under sink water filter, as one of the drawbacks of this type of system is that they generate waste water to produce filtered water. 

This is typically measured as a ratio represented like 1:3, which means that to produce 1 gallon of filtered water, it produces 3 gallons of wastewater.

A 1:3 waste water ratio is common for a typical RO system, but some modern systems are now able to generate much less waste water, some as good as 1:1, combining new technology and permeate pumps to increase water pressure and their efficiency.

Remineralization

Some under sink water filters, and particularly Reverse Osmosis systems, during the filtration process, will remove some important minerals like calcium and magnesium.

Some filters add up minerals on the last stage of the filtration process, remineralizing the water with healthy minerals.

This is not essential if you have a balanced diet, because that is enough to get the magnesium and calcium you need from your food.

What Is an Under-Sink Water Filter?

As the name says, an under-sink water filter is a water filter placed under the sink that filters water on-demand, being able to produce unlimited amounts of water when you turn on the faucet, instead of having to wait some time for the water to be filtered first.

It is a point-of-use (POU) system as it only filters water at the point it’s used, in this case, in the sink faucet. A point-of-entry (POE) system like a whole house water filtration system is capable of filtering the water of the entire house, not only of a specific point.

A conventional or typical under-sink water filter connects to the cold water pipe and sends the filtered water through a specific faucet.

Some simple under-sink water filters won’t come with a specific faucet, as you connect it directly to the sink cold water line and all the water passes through it before it reaches the regular faucet.

The Different Types of Under Sink Water Filters And How They Work

As mentioned before, there are 2 types of under sink water filters, the simple and regular (or conventional), with slightly different ways of working.

Simple Under Sink Water Filter:

This type of under sink water filter is connected to the cold water line and the water is diverted to go through this filter.

This way, all the cold water is filtered when it passes by the water filter, going back to the pipes and flowing by the regular faucet.

The simple under sink water filter is typically cheaper than the conventional one, and it is also simple to install as you don’t need to install a specific faucet.

Conventional Under Sink Water Filter:

The conventional under sink water filter is also connected to the cold water line, but it doesn’t go back to the line.

It is then connected to a specific separate faucet, and all the filtered water goes through this faucet, while the regular faucet only gets regular water that didn’t pass through the water filter.

Usually, the filter cartridge of this type of filter will last longer than the simple under sink filter because not all the water passes through it, only the part of the water that you want to filter.

Undersink vs Countertop Water Filters

Both under sink and countertop water filter systems are good options if you want clean water to drink, but they have some differences that might make one of them better for your specific situation.

On the table below you can understand how they compare against each other:

Feature	Under Sink Water Filter	Countertop Water Filter
Filtration	Good capacity and advanced filtration processes	Good capacity and advanced filtration processes
Location	In a cabinet under the sink, so in a more hidden location	On the countertop, so it will take some countertop space. Also, because it will be visible, the design will be more important.
Size	Larger than countertop as they will be hidden under the sink	Typically more compact to save countertop space
Capacity	Because they are larger, they typically have more capacity which means the filter cartridge needs to be replaced less often	Due to their compact design, the capacity is typically lower than an under sink water filter
Installation	More complex than the countertop water filter, as you may have to drill a hole in your sink to install an additional faucet	Easy to install, as you only need to connect an adapter to the faucet.
Cost	Affordable, but on average more expensive than a countertop water filter	Affordable
Reverse Osmosis System	There are RO under sink water filter systems	There are RO countertop water filter systems
POE or POU	Point-of-Use	Point-of-Use

Undersink vs Whole-House Water Filters

You might be wondering if you need an under sink or a whole house water filter for your specific situation.

In the table below you can understand how these systems compare against each other, to make the best choice for you.

Feature	Under Sink Water Filter	Whole House Water Filter
Filtration	Good capacity and advanced filtration processes	Good capacity and advanced filtration processes
Location	In a cabinet under the sink, so in a more hidden location	The system is installed at the point of entry of the water in your house
Size	Large systems, but will be hidden under the sink	Large systems as need to have the capacity to filter all the house water
Capacity	Because they are large systems designed to filter the water of  just one point, the sink, they will last longer and the filter cartridge needs to be replaced less often	These systems are designed to filter all the water of your home so they will have a large capacity and the filters will last long, typically more than 6 months
Installation	Relatively easy and straightforward, but you may have to drill a hole in your sink to install an additional faucet	More complex installation process
Cost	Affordable	Expensive, when compared with under sink water filters
Reverse Osmosis System	There are RO under sink water filter systems	Typically RO is not used for whole house water filters as they produce waste water, and that wouldn’t be efficient to filter all the water in your home
POE or POU	Point-of-Use	Point-of-Entry

Conventional Under Sink Water Filter System vs Reverse Osmosis System

You may have decided to for an under sink water filter, but you are still wondering if you should go for a conventional system or a Reverse Osmosis system.

Both systems are good options, but in our view, 2 major factors differentiate them and might help you to decide.

A Reverse Osmosis system removes a diverse amount of contaminants, as the RO process is a powerful filtration method that combines different filters and filtration stages to provide pure water.

On the other hand, a Reverse Osmosis system generates waste water, so for each gallon of filtered water is wastes between 1 gallon (efficient system) to 3 gallons (typical RO systems), which is a problem that you won’t have with a conventional under sink water filtration system.

Under Sink Water Filter Benefits

Removes Contaminants & Impurities from Your Water

The main benefit of an under sink water filter, like any water filter, it’s their ability to remove harmful contaminants and impurities from your water, improving its quality.

An under-sink water filter can remove impurities, sediments, heavy metals, chlorine, arsenic, bacteria, viruses, nitrates, etc., to ensure that you and your family have access to clean and fresh water to drink.

Improve Water Taste & Odor

Under sink water filters can improve the taste and odor of your water, because some of the removed contaminants are not only bad for your health, they are also responsible for the bad taste and odor.

An activated carbon filter is especially efficient at removing bad taste from the water, and most of the under sink water filters will have one of these filters.

Countertop Space Saving

One of the good things about under sink water filters is that they are hidden under the counter, so there is no need to take important countertop real estate like a countertop water filter does.

Even if it takes more space and is generally less aesthetically pleasing than a countertop water filter, that is not a problem because it stays in a closed cabinet.

Environment-friendly

By using an under sink water filter system you will heavily reduce your bottled water consumption, which is really beneficial for the environment.

With this choice, you will reduce the amount of plastic waste in our oceans.

Cost

There are some costs associated with buying an under sink water filter, not only the initial cost but also the recurring costs associated with replacing the filters periodically.

But the cost of this type of water filter is not that high, and they are less expensive than other types of water filters.

Their durability and high efficiency in removing contaminants make this type of water filter a really good cost-effective option.

And if currently you spend money buying bottled water, buying an under sink water filter is a no-brainer option – you will save lots of money in the long run.

Easy to Maintain

Under sink water filter systems need some maintenance, as you need to change the filters with a pre-determined frequency.

But this is a simple task that you can do in a few minutes, as most of the systems are designed to make this activity user-friendly.

And the capacity & lifespan of most under sink water filters are longer than other water filter types, like countertop or faucet filters, so you don’t need to replace the filters quite as often.

Under Sink Water Filter Disadvantages

Single Point of Use (POU)

While a whole house water filter can filter the water of your entire house, an under sink water filter can only filter the water that comes through one faucet, so it works only on a single point.

If you need more points in your house with filtered water, you will need to buy additional filters, which is not ideal if that is your situation.

Separate Faucet

For the conventional under sink water filters, there is a need to install a separate faucet that delivers the filtered water.

This faucet comes with the device but implies that you will have more effort installing it.

Installation

While the installation of an under sink water filter is not overly complicated and can be done by people with basic manual skills, it requires more effort and manual labor than the installation of other types of water filters, like countertop or faucet water filters.

And if you choose a conventional under sink water filter, you might need to drill through your countertop to install a separate faucet, if your countertop isn’t already prepared with a pre-drilled hole, making the installation process a bit more complex.

Is an Under-Sink Water Filter Right For Me?

There are different factors to consider if an under sink water filter is the right choice for your situation.

If your water is contaminated and you want access to clean and pure water, a water filter is a good solution.

If you and your family need a significant amount of clean water to drink and cook on-demand, without having to wait some time for the water to be filtered, an under sink water filter is a good option.

Another good reason to opt for an under sink water filter is If you have enough space under the kitchen sink and you don’t want to use your countertop space with a water filter.

If you are spending lots of money on bottled water, an under sink water filter will give you better quality water at a fraction of the cost of bottled water.

On the other hand, if you don’t need much water, you don’t need to remove many contaminants because your water is relatively clean, you have a tight budget, and have time to wait for filtered water, a water filter pitcher might be a better choice for you.

And if you need to get filtered water not just in one location, the kitchen sink, but on the entire house, a whole house water filter might be a better choice.

One of the reasons to not opt for an under sink filter is if you are renting and the countertop doesn’t have a pre-drilled hole for the additional faucet, maybe it is not the solution for you because you would have to drill the countertop. In this case, a countertop water filter would be a better choice for you.

How to Install an Undersink Water Filter

Each under-sink model might have its specific installation process, so you should always follow the manufacturer’s instructions and video to understand the proper installation process.

Below we will give you an idea of the usual steps involved in the installation of a conventional under sink water filter.

Step #1: Turn off and Disconnect the Cold Water

Before starting the installation, turn the shut-off valve to turn off the cold water, and disconnect the cold water line.

You can use a towel to clean some water that was on the pipes.

Step #2: Select the Water Filter Location

Select the location where you want to place the under sink water filter, and put the filter in place. Take into consideration that you need to leave some space to be able to change the filters from time to time.

Step #3: Connect the FIlter to the Cold Water Supply

Now you need to connect the cold water line to the under sink water filter system.

Step #4: Install the Faucet

If you need to install a faucet, this is the time to do it. If your sink does not have a pre-drilled hole, you will need to drill a hole on it.

This is the most complicated step so make sure you take the necessary precautions. Use the right tools and wear safety glasses.

After drilling the hole in your sink, place the faucet in it and align it in the right direction, and connect the tubes at the bottom of it to the water filter.

Step #5: Mount the Water Filter

You can now secure the under sink water filter to the side you selected. As mentioned before, just make sure that you have room to change the filters in the future.

Step #6: Turn the Water Back On

Turn the water on and check if there are any leaks or defects in the installed system.

Step #7: Test the System

Finally, you need to test it to check that it’s working properly. Turn on the faucet to let the water run for a few minutes to flush it out.

If you have to install a simple under sink water filter system, the installation process is even easier as you don’t have to worry about the additional faucet.

Just connect the filter directly to the cold line, integrating the under sink water filter system into the path of the cold water supply.

If you selected a Reverse Osmosis under sink water system, you can find how to install a Reverse Osmosis System in 10 steps in our RO review guide.

Under Sink Water Filter Maintenance

The under sink water filter maintenance is simple, and there are only two main topics to consider: when and how to change the filter cartridges.

When to Change the Under Sink Water Filter Cartridge?

There is no direct answer to this question because it depends on the model you choose, and the replacement frequency can vary a lot.

In some models, you may need to change the filter every 6 months, others work properly for 2 to 3 years until you need to change the filter.

Of course, if you are a heavy user or if your water is heavily contaminated, you may need to change the filter more frequently than indicated.

How to Change the Under Sink Water Filter Cartridge?

The process to change the filter cartridge of an under sink water filter is usually straightforward.

You just need to turn off the water supply, open the case where the filter is, remove the old filter, replace it with the new one, and close the case.

Then just let the water run for a few minutes to check if everything is working properly.

FAQ About Under Sink Water Filters

Here are some answers to frequently asked questions about undersink water filters.

How much does an under sink water filter cost?

There are different types of under sink water filters, which will have an impact on the cost. So you can find under sink water filters from $100 up to $500.

Take also into account a recurrent cost associated with the replacement of filters.

And if you have to hire a plumber to install the under sink water filter, add an additional $100 to $200 to your budget.

Should I get an under sink water filter system or an RO system?

In this case, you can have the best of both worlds as some under sink water filters are Reverse Osmosis systems.

You can choose a conventional under sink water filter or a Reverse Osmosis under sink water filter, and the big difference is that typically the RO system can remove more contaminants as it goes through several filtration stages and uses RO process to clean the water.

Can I install an undersink water filter myself, and change the filters?

Today the under sink water filters are relatively easy to install, and the manufacturers provide easy step-by-step instructions and detailed videos to show you how to do it by yourself.

So, if you have some manual ability, you should be able to do it by yourself without any problem.

Changing the filter’s cartridge is an easy activity that for sure you can do by yourself.

Is under sink water filter water better than bottled water?

With both options, you will have clean water, but the big difference is that if you drink filtered water instead of bottled water, you will reduce the amount of plastic waste generated by the bottles, reducing your environmental footprint.

Another benefit is the amount of money you will save because the initial investment on an under sink water filter will be quickly paid by the amount of money saved for not buying bottled water.

Our Verdict

After reading our comprehensive guide and detailed under sink water filter reviews, you are in a good position to select the best model for your home.

Any of the options we presented would be a good choice to deliver filtered water for you and your family to drink and cook.

For us, the best overall choice is the Waterdrop G3 Reverse Osmosis Under Sink Water Filter System, but all the under sink water filters we listed are great options, so you can’t go wrong with any of these options!