Common tap water may contain contaminants due to the pipes it travels through and chemicals used in the municipal filtration process. For families who want easy access to filtered tap water for daily drinking and cooking, an under-sink water filtration system is a convenient solution.
Countertop water filters can be effective, but may also be a bit of an eyesore and take up valuable counter space. Under-counter models keep the mechanics out of sight while providing filtered water right at the kitchen sink. The best under sink water filters have multiple levels of filtration to offer clean tap water right at your fingertips.
- BEST OVERALL: iSpring RCC7P-AK 6-Stage Reverse Osmosis System
- RUNNER UP: Express Water RO5DX Reverse Osmosis Filtration System
- BEST BUDGET: Waterdrop 15UA Water Filter System
- BEST TANKLESS: Waterdrop RO System
- BEST FAUCET OPTIONS: Aquasana AQ-5200.62 2-Stage Water Filter System
- BEST FOR ALKALINE WATER: APEC Water Systems ROES-PH75 Essence Series
- BEST FOR WELL WATER: Home Master TMHP HydroPerfection RO System
Types of Under Sink Water Filters
Options for under-sink water filters range from a simple attachment for an existing cold-water line and faucet to a more complex multi-stage system. Common types include reverse osmosis, ultrafiltration, and carbon water filters.
Reverse Osmosis (RO)
RO systems flush contaminants from the water supply to deliver filtered water through a separate faucet. The system works by pushing water through a membrane with pores so small that only water molecules can pass through, eliminating more than 1,000 toxins such as chlorine, fluoride, and heavy metals, as well as bacteria and pesticides.
The most effective versions have multiple levels of filtration, including carbon water filters, so they may take up a considerable amount of cabinet space and include a moderately complex DIY installation.
Ultrafiltration uses a hollow fiber membrane to stop debris and contaminants from entering the water. Though it doesn’t eliminate as many toxins as an RO system, it will preserve healthy minerals that are eliminated in systems where only water molecules can pass through.
It is also easier to install, as it generally works as an addition to the existing faucet. However, since it attaches to the main faucet, the filter may need to be changed more frequently than systems with a separate fixture.
A carbon filter is the most basic option when it comes to filtration, but still very effective. It is used in various systems from simple water pitchers to advanced multi-level systems. Activated carbon will chemically bond with contaminants, removing them as water flows through the filter.
The effectiveness of a carbon filter alone will vary, so look for the level of filtration noted on the product, including the contaminants it will remove. An RO system combined with a carbon filter is generally the best under-sink water filter systems for eliminating toxins from tap water.
What to Consider When Choosing the Best Under Sink Water Filter
There are plenty of options available when it comes to water filtration. The best under-sink filtration system should suit the user’s space, capacity, and installation needs while providing easy access to clean water. Other things to consider while shopping include types and levels of filtration, water flow and pressure, odor removal, and water waste.
Size and Capacity
The size and type of water filtration needed will depend on the amount of filtered water required by a household each day. For those who live alone, a pitcher or simple under-sink attachment should suffice. For large families who tend to use a lot of filtered drinking or cooking water, an RO system can easily filter anywhere from 50 to 75 gallons of water per day.
Although larger capacity filtering cartridges require replacement less frequently, they take up more space beneath the sink, especially RO systems that come with a tank. For those with limited cabinet space, this is an important consideration.
The flow rate measures how quickly water is dispensed from the faucet. This will impact how long it takes to fill a glass or a pot for cooking. The more levels of filtration, the slower the water will flow from the faucet, so companies work hard in this area to offer faster flow as a selling point. RO systems have a separate faucet; however, for filters that use the main faucet, users may notice a very slight reduction in water flow.
The rate is calculated by gallons per minute (GPM) and depending on the product, will typically range from 0.8 to 2 GPM. The flow rate is not only dictated by the product, but also by the pressure of the home’s water supply and the number of people using it.
While flow rate is reflected by speed, water pressure is determined by force. Very low water pressure will inhibit proper filtration through RO filters since the system relies on pressure to force water molecules through the membrane. A home’s water pressure is measured in pounds-per-square-inch (psi).
Many large under-sink filters will require a minimum of 40 to 45 psi to be effective. For a standard household, the maximum psi will normally be 60. Water pressure will also be affected by the square footage of the house, as well as the number of users within the household.
According to a recent Consumer Reports survey, nearly half of Americans who drink municipal water complained of an odor coming from their tap water. Though the odor doesn’t always mean something is wrong, it can make hydrating less appealing. Chlorine is one of the most common contributors to the smell, a chemical used in water-treatment facilities to rid the water of bacteria, viruses, and parasites.
Fortunately, most water filters, even pitchers, will help to reduce the odor and enhance the taste. The higher level of filtration, the more efficient the system will be at removing both the contaminants and the resulting odor.
As previously mentioned, many RO under-sink filters will include a separate dedicated faucet. Many drop-in sinks will include pre-fabricated holes—some may need to be punched out—that can accommodate a secondary faucet.
However, others will require a new hole to be drilled, which may be a drawback for some. Shoppers may also want to take note of the style of the faucet to make sure it works with their design aesthetic. Most feature a slim silhouette in brass and are finished with brushed nickel or chrome. Some manufacturers will offer a choice of finishes.
Filtration system installations range from a simple DIY project that takes minutes to a more detailed job that may require professional help, depending on your level of handiness. Those using the main faucet as the water source will require less time and sweat for installation, which usually entails attaching the filter to the cold-water line.
Though still simpler than a whole house filtration system, RO under-sink filters with a separate water dispenser can be more involved. Depending on whether there is a predrilled hole available for an extra faucet and how much space is available under the sink, a system can take minutes or hours to install. Many companies will offer guides, videos, or phone support to help with the process.
One drawback to RO systems is that a decent portion of water may be wasted during the filtering process when waste is flushed away. Some systems have a ratio as high as 3 gallons wasted to 1 filtered. Thanks to new technologies, such as a special pump called a permeate pump to increase water pressure, this waste is reduced. Others will include a setting to use wastewater for non-drinking purposes. Shoppers should aim for a low waste-to-pure water ratio.
Our Top Picks
The best under-sink water filters will provide effective filtration, access to ample clean water, and a relatively easy installation. The following under-sink filter systems include these and other features for those looking to add the convenience of filtered water at the kitchen sink.
Talk about thorough: This reverse osmosis system from iSpring removes up to 99 percent of more than 1,000 contaminants found in tap water, including lead, arsenic, chlorine, fluoride, and asbestos. Its impressive six stages of filtration include sediment and carbon filters to remove large contaminants and protect the reverse osmosis membrane from chemicals like chlorine and chloramines.
The reverse osmosis filter removes contaminants down to 0.0001 microns, so that only water molecules can fit through. An alkaline remineralization filter restores healthy minerals lost in the filtration process, and the last filtration stage gives the water a final polish before being delivered to the included brass faucet, which has a sleek, brushed nickel design.
An electric pump boosts the water pressure so there is less waste during the filtration process, with a ratio of 1 filtered to 1.5 wasted gallons. Filters need to be replaced every six months to a year. Installation can be done by the user with the help of the company’s written and video guides. Live phone support is available for those who run into any problems or have questions not covered by the provided guides.
- Type: Reverse osmosis
- Capacity: 75 gallons
- Flow Rate: 1.0 GPM
- Capable of removing 1,000 contaminants through 6 filtration stages
- Electric pump aids water pressure
- Brass faucet and reverse osmosis filter included
- Easy to install; written and video instructions included
- Expensive compared to other systems
Thanks to a collection of easy-to-install fittings and upgrades, such as ultraviolet, alkaline, and deionization filters, this reverse osmosis system with five stages of filtration is an excellent solution for just about any home that uses municipal water.
In this system, the water first passes through a sediment and two carbon filters before reaching the RO membrane, which removes the finest contaminants. The last stage features a third carbon filter, which aims to eliminate any lingering toxins.
The system is budget-friendly and comes with four replacement filters, which need to be changed twice a year. One drawback with this system is there is no pump, so water waste comes out to about 1 to 3 gallons.
- Type: Reverse osmosis and carbon filtration
- Capacity: 4 gallons
- Flow Rate: 0.8 GPM
- Budget-friendly system
- 5-stage filtration; ultraviolet, alkaline, and deionization filters
- 4 replacement filters included
- Slightly large; takes up more space than other systems
Water filtration doesn’t need to cost an arm and a leg, and installing a filtration system doesn’t need to take up an entire weekend. This affordable under-sink water filter systems from Waterdrop can be installed in three minutes, making accessing clean tap water a cinch.
This model is also a great option for shoppers who don’t have the cabinet space for a larger filtration system. The small attachment connects directly to the cold-water line and dispenses carbon-filtered water from the main faucet, reducing odor and pollutants such as chlorine, sediment, rust, and other heavy metals. While it doesn’t eliminate as many contaminants as an RO system, it does retain healthy minerals, like calcium, potassium, and magnesium.
Waterdrop boasts an easy installation with its push-to-connect fittings, and a twist-and-lock system that makes changing filters easy. For simple upkeep, each filter has a maximum service life of 24 months or 16,000 gallons.
- Type: Carbon filtration
- Capacity: 16,000 gallons
- Flow Rate: 0.75 GPM
- Affordable system
- Removes heavy metals with 3-stage carbon filtration
- Filters last for up to 2 years
- 3-minute installation process
- Not suitable for well water
Another great option from Waterdrop for kitchens with limited under-sink space, this sleekly designed tankless RO system has a compact footprint without skimping on special features. new technologies make for a smart operation. An internal pump offers faster water flow and less waste with a 1 to 1 ratio of filtered to wastewater, while a leak detector cuts off the water in the event of leaky pipes.
Three filters provide multiple levels of cleansing, including sediment and carbon block filters, an RO membrane, and an activated carbon block filter, which uses activated carbon granules made from natural coconut shells to improve water taste. A helpful indicator light will change colors when it is time to replace the filters. Use the included manual or online tutorial to help with installation. One thing to note is the system needs to be flushed out for 30 minutes before use.
- Type: Reverse osmosis
- Capacity: 400 gallons
- Flow Rate: 400 GPD
- 3-stage carbon filtration process with RO membrane
- Water pump reduces water waste and increased water pressure
- Leak detector and faucet included
- Compact design
- Needs 30 minute flush before use
- More expensive compared to other systems
Shoppers interested in incorporating a new faucet with their under-sink water filter should consider this model from Aquasana. Available in three stylish finishes to match a variety of kitchen decors, the system has two stages of filtration and can remove up to 99 percent of 77 different contaminants, including lead and mercury, as well as 97 percent of chlorine and chloramines. The filters are made to be environmentally-friendly with minimal disposable plastic parts.
Since the system does not use an RO membrane, there is no water waste, and the filtering process will retain healthy minerals. It has a filter life of around 600 gallons, which can last up to six months. Installation can be done by the owner with the help of a detailed manual.
- Type: Carbon filtration
- Capacity: 500 gallons
- Flow Rate: 0.5 GPM
- Capable of filtering 77 contaminants with a 2-stage filtration system
- Environmentally-friendly filters
- Water-saving design
- Includes faucet; choice between 3 finishes
- Similar sets come with more options for faucet finish
For those looking for a long-term water filtration solution, this carbon-filter model from CuZn is in a class of its own. While most under-sink filters can last between six months and two years, this model boasts a whopping five-year lifespan. This filter is designed to purify up to 50,000 gallons of municipal water.
Its three-stage filtration process creates a bacteriostatic environment within the system that resists mold and bacteria growth to make it last longer. This, combined with a sediment and carbon filter, efficiently removes chlorine, heavy metals, and other contaminants.
The filter is on the larger side, but is still more compact than those with an added tank. It should not be used in homes that use well water. It also boasts a fast flow rate and zero water waste.
- Type: Reverse osmosis
- Capacity: 75 gallons
- Flow Rate: 75 GPD
- 3-stage sediment and carbon filtration
- Filters 1,000+ contaminants including heavy metals and chlorine
- Water-saving design
- Long lifespan (5 years)
- Larger than comparable systems; less suitable for small spaces
- Does not filter well water
While plain water is just fine for plenty of people, some prefer the taste and purported health benefits of drinking alkaline water. Thanks to a mineral cartridge that adds high-purity calcium carbonate back into the filtered water, alkaline water drinkers can now enjoy this higher pH beverage straight from the tap by using this filter from APEC Water Systems.
In terms of filtration, double carbon blocks and an RO membrane work to eliminate 99 percent of more than 1,000 contaminants, including chlorine, fluoride, arsenic, lead, and heavy metals. A reliable choice, the system has been certified by the Water Quality Association (WQA), which ensures high-quality water filtration products.
A sleek brushed nickel faucet is included with the filter. Keep in mind that there is water waste to consider with this filter, as it has a slightly high 1 (filtered) to 3 (waste) gallon ratio. Videos and a manual are available for those who opt for DIY installation.
- Type: Reverse osmosis
- Capacity: 2,000 gallons
- Flow Rate: 50 GPD
- Double carbon and ultraviolet filtration system removes 1,000+ contaminants
- Adds calcium carbonate and balances water pH
- Faucet included
- Easy to install
- Wastes water while filtering (1 gallon filtered to 3 gallon waste ratio)
- Slightly large; may not be suitable for small under sink spaces
Selected for its 6-stage filtration that removes over 1,000 contaminants, built-in water pump, and an included brass faucet, the iSpring under-sink filter system is our top pick. Alternatively, the Waterdrop under-sink filter system is a more affordable and compact option suitable for small spaces. While it has fewer filtration stages, its carbon filter can remove heavy metals and the filters last for up to 2 years (compared to the typical 6-12 months).
How We Chose the Best Under Sink Water Filters
After evaluating the key aspects that go into under-sink water filtration—the amount of contaminants removed, physical size of the system, and number of filtration stages—the above list reflects thorough research into the most suitable products across different price points and filtration types.
Many of the featured under-sink water filter systems can filter municipal water, well water, and alkaline water to remove over 1,000+ contaminants including chlorine, heavy metals, and bacteria. Some of the filters come with countertop faucets, saving the need for a separate (and potentially more costly) purchase. Select systems also stood out for their water-saving designs and built-in pumps that improve water pressure as well as replacement filters.
You may still be wondering about which filter removes the most contaminants, how to choose the right under-sink water filter for your home, and how often the filter needs to be changed. Read on for the answers to these and other commonly asked questions about under-sink water filters.
Q: Which water filter removes the most contaminants?
A reverse osmosis water filtration system combined with a carbon filter is the most effective option for removing as many contaminants as possible.
Q: How do I choose an under-sink water filter?
Three important things to consider when choosing the best under-sink water filtration systems are under-counter space, the amount of filtration desired, and the difficulty level of installation you’re willing to take on.
Q: How often should I change my under-sink filter?
The timeframe for changing your under-sink filter will depend on the model you choose. It’s important to read the manufacturer’s instructions. Most will have a lifespan of six months to a year.
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