What is an Under Sink Water Filter?
An under sink water filter is a type of water filtration system that is installed below a sink to remove contaminants from water that will be used for drinking, cooking, cleaning, and other uses. Typically, under sink water filters are installed in the kitchen because it will be the most widely used sink in the home — although they can also be installed in bathrooms or other sinks if desired.
How Do Under Sink Water Filters Work?
Under sink water filters work using one or more filtration methods which include:
Mechanical
Mechanical filtration involves the use of a barrier to catch contaminants as water passes through. These filters can range from a basic mesh to a more complex pore structure. While mechanical filtration is a good starting point, it can’t be relied on as the sole filtration method because it does not remove chemical contaminants. As a result, many under sink water filters use mechanical filtration as the first stage in combination with other methods that will make water safe for use.
Activated Carbon
Activated carbon (or charcoal) comes from organic material with high carbon content including wood, coal, and coconut shells — which is heated to form a porous char. As water passes through, contaminants stick and chemically bind to the activated carbon through a process called adsorption. The effectiveness of activated carbon filters varies greatly, some remove harmful contaminants like lead while others are only able to remove chlorine to improve taste and smell. Additionally, activated carbon filters cannot remove inorganic contaminants — so you’ll need to use this in combination with other filtration methods.
Ion Exchange
Ion exchange is typically intended to treat hard water rather than remove contaminants, as it works by swapping calcium and magnesium ions (which cause hard water) with harmless sodium ions. Since contaminants including organic material and bacteria remain, you’ll need to use this filtration method in combination with others.
Reverse Osmosis
Reverse osmosis is the most effective water filtration method. These filters work by pushing highly pressurized water through a semi-permeable membrane. During the process, contaminants are left behind as only clean water is able to pass through. It’s important to note that reverse osmosis water filters are so powerful that they often remove beneficial minerals which are good for your health. To make sure your water retains these minerals, look for a system with remineralization technology.
Buyer’s Guide for Under Sink Water Filters
Comparing under sink water filter features and reading reviews is a great starting point, but choosing the best system for your home requires additional insight. This page will provide you with information about the benefits of these systems, details on how they work and more, so you can make the most informed selection of a system for your home.
Benefits of Under Sink Water Filters
Under sink water filters can help you enjoy water that tastes better and is safer for your health. Here’s some additional information on the benefits of these systems:
Remove Harmful Contaminants
Under sink filters are highly effective at removing contaminants, especially compared to countertop systems including pitcher filters. This is because most countertop and pitcher filters rely on a single-stage of filtration with one method, usually activated carbon. By comparison, most under sink water filters feature two or more stages of filtration and a combination of methods. As noted in the section above, one filtration method is usually not enough to make water safe for use. By increasing the stages of filtration and using a combination of methods, multi-stage under sink systems are able to remove more contaminants from tap water.
Improve Water Taste, Smell, and Appearance
The contaminants in your water aren’t just bad for your health, they also affect the taste, smell, and appearance of it. By using an under sink water filter to remove contaminants, you’ll notice water that looks clearer, doesn’t smell, and tastes great. Maybe it’s the extra boost you need to start drinking more water each day.
Focused
Under sink water filters are point-of-use filters, meaning the water is filtered right when you want to use it. This differs from point-of-entry filters like whole house systems, which filter water when it enters the main water line in your home. While whole house systems are a great way to remove contaminants from water before it gets to your home, there’s still a chance the water can be contaminated from the pipes in your home.
If water comes in through the main water line, gets filtered through a whole house system, then passes through pipes containing contaminants before coming out of your faucet — you risk exposure to unsafe water. By comparison, a point-of-use system will filter water right before it comes out of the faucet so there’s no potential for recontamination. If you live in an older home, your pipes may contain lead, so a point-of-use system like an under sink water filter is recommended.
Additionally, most whole house systems don’t remove as many contaminants as under sink systems.
Flexible
Under sink filters offer great mobility due to their small size and easy installation/removal process. If you’re renting and want a system that can be transported and installed from home-to-home, under sink water filters are a great choice. The exception to this are under sink systems that require a new faucet to be installed, so if mobility is important to you — choose a system that works with any existing faucet.
Space Efficient
Under sink water filters are a great way to get filtered water without giving up valuable countertop or fridge space. Countertop systems and pitchers require the filter to be accessible in order to use it, but under sink systems can be installed in a cabinet where they’ll be hidden.
Under sink water filters are a great way to get filtered water without giving up valuable countertop or fridge space. Countertop systems and pitchers require the filter to be accessible in order to use it, but under sink systems can be installed in a cabinet where they’ll be hidden.
Affordable
Price is an important factor in any purchase decision, and when it comes to water filters you’ll find that options can range from less than $100 to over $1,000. Typically, whole house systems are the most expensive while pitcher filters are the cheapest option — which aligns closely with their performance in removing contaminants and/or gallons filtered. Under sink water filters fall near the middle, usually offering a balance of performance while still being affordable. There’s also a wide range of systems to choose from. You could opt for a low cost single-stage under sink filter, or a more expensive reverse osmosis system that offers greater performance. The choice is yours depending on your budget and concern about contaminants.
Under Sink Water Filters
Aquasana - Claryum® 3-Stage - AQ-5300
The Claryum® 3-Stage instantly transforms your ordinary tap water into clean, great-tasting water for 600 gallons or up to 6 months. The Claryum® 3-Stage includes a Pre-Filter to extend the life of your system, improve effectiveness, and increase performance. Independantly tested and certified for remove up to 99% of 78 contaminants including mercury, chlorine-resistant cysts, herbicides, pesticides, VOCs, pharmaceuticals, and more. The included all-metal dedicated faucet comes in three finishes – Brushed Nickel, Chrome, and Oil Rubbed Bronze.
Learn More about the Aquasana - AQ-5300Best Price*
Cost Per Gallon*
$0.12
System
$154.99
Replacement Cost
$69.99
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53, 401
Capacity
600 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.12
System
$154.99
Replacement
$69.99
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53, 401
Capacity
600 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- Eco-friendly
- 90-day satisfaction guarantee
- 1-year warranty
- Easy install
- Filter replacement subscription option
- Faucet finish options
- Electronic filter life indicator
Aquasana - Claryum® 3-Stage Max Flow - AQ-5300+
With a 44% faster flow rate, the Claryum® 3-Stage Max Flow instantly transforms your ordinary tap water into clean, great-tasting water for 800 gallons. Includes a Pre-Filter to extend the life of your system, improve effectiveness, and increase performance. Independantly tested and certified for remove up to 99% of 78 contaminants including mercury, chlorine-resistant cysts, herbicides, pesticides, VOCs, pharmaceuticals, and more. The included all-metal dedicated faucet comes in three finishes – Brushed Nickel, Chrome, and Oil Rubbed Bronze.
Learn More about the Aquasana - AQ-5300+Best Price*
Cost Per Gallon*
$0.10
System
$189.00
Replacement Cost
$79.99
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53, 401
Capacity
800 gal
Flow Rate (gpm)
0.72
Best Price*
Cost Per Gallon*
$0.10
System
$189.00
Replacement
$79.99
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53, 401
Capacity
800 gal
Flow Rate (gpm)
0.72
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- Eco-friendly
- 90-day satisfaction guarantee
- 1-year warranty
- Easy install
- Filter replacement subscription option
- Faucet finish options
- Electronic filter life indicator
A.O. Smith - 2-Stage Water Filter - AO-US-200
Optimally clean water for all of your water needs straight from a dedicated faucet (included). Advanced filtration reduces up to 99% of 78 harmful contaminants including lead, mercury, asbestos, pesticides, pharmaceuticals, chlorine, and more. No water is wasted, and nothing is added to your water during the filtration process. Filters last 500 gallons or 6 months and the system comes with a limited 1-year warranty.
Learn More about the A.O. Smith - AO-US-200Best Price*
Cost Per Gallon*
$0.13
System
$139.00
Replacement Cost
$65.98
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53 , 401
Capacity
500 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.13
System
$139.00
Replacement
$65.98
Performance
Total Contaminants Reduced
78
Certified
NSF/ANSI 42, 53 , 401
Capacity
500 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 1-year warranty
Culligan - EZ-Change Under-Sink Drinking Water Filter - US-EZ-4
The Culligan US-EZ-4 Premium Easy-Change Under-Sink Drinking Water Filtration System helps keep your family healthy and hydrated by providing clean water through a dedicated faucet (included with system). The Easy-Change Filter fits easily under the sink and can be installed with any sink's water system tapping into the cold water line to keep fresh water at your family's fingertips. Designed for convenience, this filter can be installed and replaced in mere minutes with the simple twist-on, twist-off mechanism and built-in quick-connect fittings. There is no need to shut the water supply off when changing the cartridge with the built-in ball and check valve in the filter head.
Learn More about the Culligan - US-EZ-4Best Price*
Cost Per Gallon*
$0.14
System
$89.37
Replacement Cost
$70.00
Performance
Total Contaminants Reduced
9
Certified
NSF/ANSI 372, 42, 53
Capacity
500 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.14
System
$89.37
Replacement
$70.00
Performance
Total Contaminants Reduced
9
Certified
NSF/ANSI 372, 42, 53
Capacity
500 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 2-year warranty
- Electronic filter life indicator
- Easy install
Culligan - Two-Stage Under Sink Filtration Drinking Water Filtration System - US-2
The Culligan US-2 Undersink Drinking Water Filtration System provides great tasting water for drinking, cooking, and ice makers. This 2 stage system includes a chrome faucet with indicator light to remind you when you change filters. Culligan filters innovative quarter turn design allow for a hassle and mess free changes. The Culligan US-2 system has a 5 GPM flow rate and reduces bad taste and odor, chlorine, particulate class 1, cysts, lead, lindane and atrazine.
Learn More about the Culligan - US-2Best Price*
Cost Per Gallon*
$0.11
System
$122.00
Replacement Cost
$65.76
Performance
Total Contaminants Reduced
5
Certified
NSF/ANSI 372, 42, 54
Capacity
500 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.11
System
$122.00
Replacement
$65.76
Performance
Total Contaminants Reduced
5
Certified
NSF/ANSI 372, 42, 54
Capacity
500 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 1-year warranty
- Electronic filter life indicator
- Easy install
3M Aqua-Pure - AP-DWS-1000 Drinking Water System - AP-DWS1000
The Aqua-Pure AP-DWS1000 removes and reduces impurities from your drinking water, including chlorine, taste, odor (CTO), particulate, turbidity, lead, VOCs, parasitic protozoan cysts, and MTBE. This system connects easily under the kitchen sink and incorporates an advanced dual stage carbon-block filtration process to help provide cleaner, clearer better tasting drinking water filtration on demand.
Learn More about the 3M Aqua-Pure - AP-DWS1000Best Price*
Cost Per Gallon*
$0.22
System
$289.00
Replacement Cost
$137.00
Performance
Total Contaminants Reduced
7
Certified
NSF/ANSI 42, 53
Capacity
625 gal
Flow Rate (gpm)
0.6
Best Price*
Cost Per Gallon*
$0.22
System
$289.00
Replacement
$137.00
Performance
Total Contaminants Reduced
7
Certified
NSF/ANSI 42, 53
Capacity
625 gal
Flow Rate (gpm)
0.6
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 30-day satisfaction guarantee
- 1-year warranty
- Easy install
Everpure - H-1200 Drinking Water System - EV928200
This dual-cartridge system provides extra protection against a variety of contaminants, including MTBE, and boasts a longer lifespan compared to single cartridge systems. The Pentair Everpure H Series filtration systems with exclusive Micro-Pure filtration technology reduces potentially harmful contaminants that may be in your family’s drinking water. With an Everpure System in your home, everything you make will taste better: coffee, tea, flavored water mixes, juices, soups, and even ice cubes.
Learn More about the Everpure - EV928200Best Price*
Cost Per Gallon*
$0.16
System
$696.00
Replacement Cost
$198.88
Performance
Total Contaminants Reduced
5
Certified
NSF/ANSI 42, 53
Capacity
1,000 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.16
System
$696.00
Replacement
$198.88
Performance
Total Contaminants Reduced
5
Certified
NSF/ANSI 42, 53
Capacity
1,000 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 1-year warranty
- Easy install
Premier - UF3 Under Counter Filtration - WP531130
The Watts Premier Filter-Pure UF-3 Water Filtration Device utilizes three-stage filtration to ensure you get cleaner, healthier drinking water straight from the tap. In addition to reducing lead, chemicals, and chlorine taste and odor, the UF-3 uses Hollow-Fiber technology to trap and remove even the tiniest particles from your water. Featuring a patented space-saving design that is perfect for houses and apartments, the UF-3 can be installed in a matter of minutes.
Learn More about the Premier - WP531130Best Price*
Cost Per Gallon*
$0.64
System
$173.00
Replacement Cost
$96.00
Performance
Total Contaminants Reduced
72
Certified
NSF/ANSI 42, 53
Capacity
150 gal
Flow Rate (gpm)
0.5
Best Price*
Cost Per Gallon*
$0.64
System
$173.00
Replacement
$96.00
Performance
Total Contaminants Reduced
72
Certified
NSF/ANSI 42, 53
Capacity
150 gal
Flow Rate (gpm)
0.5
Key Contaminants Removed:
Lead
Chlorine
Chloramines
PFOA/PFOS
Pesticides & Herbicides
VOCs
Pharmaceuticals
Cysts
Other Benefits:
- 30-day satisfaction guarantee
- 1-year warranty
When Do You Need an Under Sink Water Filter?
Once you’ve decided you need a water filter, the next step is determining what type of system you’ll get. If you need filtered water throughout your home, a whole house system would make more sense. However, if you only want filtered water from one area like a kitchen, the choice likely comes down to an under sink or a countertop water filter. Countertop filters offer more portability and are generally cheaper, but also offer reduced performance. By comparison, under sink water filters offer higher performance but are typically more expensive.
An under sink water filter is ideal if you want filtered water from one location (typically a kitchen), and want a higher level of contamination removal than what is offered by countertop alternatives. If you don’t want to spend a lot, go for a lower level of filtration like a one or two-stage option. On the other hand, a reverse osmosis system will provide maximum contaminant removal at a higher price point.
How to Choose the Best Under Sink Water Filter for your Home
When comparing under sink water filters and reading reviews, you’ll get a lot of information and it can be hard to know what’s important. The following factors are what you should look at for every system you’re considering.
Certifications
You shouldn’t just assume that any filter will make your water safe to drink, you need to verify the system you’re considering will be effective in removing the contaminants you’re concerned about.
Before purchasing any under sink water filter, make sure it has certifications from one or more independent third-party agencies like the International Association of Plumbing and Mechanical Officials (IAPMO), the National Sanitation Foundation (NSF), or the Water Quality Association (WQA).
These third-party agencies are not associated with the company selling the products, so you get unbiased information verifying their effectiveness. The agencies will rigorously test filters and use strict standards to ensure they will actually remove or reduce contaminants to the levels the company claims to. After testing has concluded, the agency will provide a certification (usually in the form of a logo or seal) that can be used in the product packaging or marketing messaging.
When looking for the best under sink water filter for your home, consider what contaminants are most concerning to you, then look for certifications verifying the filter you’re looking at will remove those contaminants. For example, if you live in a home with lead pipes and are worried about it contaminating your water, make sure the under sink system you’re looking at is certified to remove lead to a high degree.
Size and Filter Capacity
How much space do you have under your sink? Before purchasing an under sink system, make sure you have enough space for it to fit. If you have limited space, you may need to consider a smaller system like a two-stage filter, whereas more space would allow you to fit a larger and more powerful alternative like a reverse osmosis filter.
Beyond the space you have available, you’ll also need to consider the number of people in your home and anticipated usage which relate to filter capacity. If you only have 1-2 people in your home, a lower capacity filter will suffice. However, a home with 3 or more people means higher usage so you’d want a filter with a larger capacity to meet the increased demand.
Filter capacity shouldn’t be overlooked, as choosing a filter with a capacity larger than what you need adds unnecessary cost because you’ll likely need to replace it before reaching close to the limit. In contrast, choosing a filter with a small capacity for your household means you’ll have to replace filters often and risk overworking the system leading to working less effectively.
Cost
For many, cost is the first purchasing factor to consider. Based on your budget, you can immediately eliminate filters that are beyond the price range you’re willing to spend.
In general, you’ll find the most affordable under sink water filters are usually two-stage options, while the most expensive systems utilize reverse osmosis. Cost typically correlates with performance, as the single-stage systems are usually the least effective options while RO filters are the most effective. If you’re looking for a balance of cost and performance, a three or more stage filter will usually offer the best of both.
When taking cost into consideration, don’t forget about the price of replacement filters. For any system, look at the recommended filter replacement schedule and the cost of those filters. Annual replacements for multi-stage filters may add $100 or more in maintenance costs.
Installation and Maintenance
While most under sink water filters are easy to install, some with more complex installation processes (like requiring a new faucet) may require professional installation from a plumber. This may be seen as an inconvenience to some, and it also has an impact on cost since you’ll need to pay for their services.
Maintenance will vary depending on the specifics of each under sink system. If the under sink system features multiple stages of filtration, these filters may require replacement filters at different time intervals. Maintenance will also vary from home to home based on usage. To maintain the life and effectiveness of the system, the homeowner should follow the recommended filter replacement schedule from the manufacturer.
Final Considerations
Hopefully, our guide provided all the information you need to make an informed decision and purchase the best under sink water filter for your home.
By now, you should know what an under sink water filter is, how it works, the benefits of these systems, factors to consider, and FAQs when comparing options. Each individual has unique needs for their home, so it’s important to have all the facts so you can make the right choice for your situation.
For more information about under sink water filters, check out our featured product reviews to learn about some of the most popular options. Get an overview of each and see the pros/cons so you can see how popular under sink water filters compare to each other.
Frequently Asked Questions
Resources
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Comparing Water Filter Technology
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*Product performance claims and prices were taken from publicly available information on Amazon, are accurate as of 9/1/2022, and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply to the purchase of this product. Cost per gallon is calculated as replacement filter price/capacity. Not all contaminants will be listed in charts. If you find information that is inaccurate, please send the correct info with supporting documentation to info@waterfiltercomparisons.com, and we will address any errors. As an Amazon Associate, Water Filter Comparisons receives a commission on purchases made through our Amazon links.