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Accessing filtered water is a must for any household. Water that’s unfiltered could have harmful chemicals, and it could taste downright bad. While there are a few ways you can filter water in your home, an under-sink water filter is among the best options, as it allows you to access clean, filtered water directly from your bathroom, kitchen sink, or RV faucets. Water pitcher systems constantly need to be refilled and cleaned, but with an under-sink system, you can have the peace of mind of having fresh drinking water at your disposal whenever you want it.
There are several types of under-sink filters available, and the price and installation can vary greatly depending on the model. Typically, you can expect to spend somewhere in the vicinity of $70-$150 on an under-sink water filter, depending on its flow rate and size.
In this comprehensive review, the This Old House Reviews team evaluated the best under-sink water filters to help you make an informed purchase and improve your water quality. Overall, our top choice is the CuZn Under-Counter Water Filter, which features a three-stage purification system and can last up to five years per cartridge. Read our guide below for more of our top picks.
Best Under-Sink Water Filters: Our Top 6 Picks
- Best Overall: CuZn Under-Counter Water Filter
- Best Reverse Osmosis System: Express Water Under-Sink Filtration System
- Best RV Water Filter: Waterdrop Under-Sink Water Filter System
- Best Design: Aquasana 2-Stage Under Sink Water Filter System
- Best Two-Stage Filter: FRIZZLIFE Under-Sink Water Filter
- Easiest Setup: Aquasana Under Sink Water Filter
Compare Top Under-Sink Water Filters
|CuZn Under-Counter Water Filter
|Express Water Under-Sink Filtration System
|Waterdrop Under-Sink Water Filter System
|Aquasana 2-Stage Under Sink Water Filter System
|FRIZZLIFE Under-Sink Water Filter
|Aquasana Under Sink Water Filter
Terms to Know for Under-Sink Water Filter
- Filter Life: This refers to how long the filter will last before it needs a replacement filter.
- Flow Rate: This refers to the maximum amount of water that could come out of your faucet or tub at once. It is measured in GPM, or gallons-per-minute.
Best Under-Sink Water Filter Overall
What Are People Saying About the CuZn Under-Counter Water Filter?
Our team found that numerous satisfied customers were pleased with this product’s easy-to-follow installation instructions. Many said the filter improved their water by removing its chemical taste and smell. However, our team also noticed that some unsatisfied customers were skeptical that this under-sink water filter truly filtered their water effectively.
“This is the second filter (replacement after 5.75 years of use) It works well to rid the water of the city additives and tastes a lot better than without a filter. I’ve tried other under-sink systems and different filtering processes. This is the best in terms of cost over time and water quality in my opinion. Easy install, no brackets to mount, one filter canister, and works well for a long time.” —J. Williams via Amazon
“After having installed this system, I am extremely skeptical about what it actually does. The PPM meter shows zero change in the water. I wish I went with an RO system that has measurable results. I feel like this is more of a gimmick without measurable results.” —Jane via Amazon
Best Reverse Osmosis System
What Are People Saying About Express Water Under-Sink Filtration System?
Many reviewers we noted said that the instructions they received with their reverse osmosis system made installation easy. Positive reviews also highlighted that the quality of their water was immediately improved. On the other hand, we also saw some unhappy customers that complained about how difficult it was to find a compatible replacement water filter and others had issues with leaking.
“Great solution for drinking water! I use this to remove sodium from softened water. The kit has everything needed for typical connections and under-sink installation. I installed it in my basement immediately below my kitchen to save space in my cabinet, which I recommend if your utility room is conveniently located relative to your kitchen. The instruction book is great — thorough and color-illustrated. Once connected it makes RO water at a good pace, faster than my old Whirlpool/Ecopure system it replaced. Comes with a set of replacement filters, and the 3-year filter kit available separately is priced fairly.” — MM-MN via Amazon
“I spent about three days trying to install the Express Water RO5DX. My biggest complaint is the system should have been fully assembled AND TESTED before shipment. During installation, there is a plastic housing that you need to screw in multiple plastic valves/connectors. The plastic tends to bend and does not really work well with Teflon tape. Even worse, you can’t use any tools to help because the plastic will just bend/snap. If the connector does leak then it’s not possible to repair it because unscrewing and re-attaching the plastic connectors will cause their threads to shave off. I managed to get the entire thing assembled, only to find one of the filters was leaking. I managed to fix get, get the entire system working, only to find one of the hoses started leaking/spraying water in the middle of the night. I spent another day trying to figure out exactly where the water was leaking from, eventually gave up and returned it.” — David via Amazon
Best RV Water Filter
What Are People Saying About the Waterdrop Under-Sink Water Filter System?
According to our research, customers who were pleased with their purchase thought this filter was easy to install, with some saying only took 10 minutes. Other reviewers noted that the flavor and clarity of their water were significantly improved. Dissatisfied customers pointed out that the water flow was weak, and the system stopped filtering after a few months.
“I bought this product because I wanted to improve the taste and quality of my tap water…. The package came with everything I needed to install the filter under my sink…. It took me less than 15 minutes to complete the installation. The filter is connected to the cold water supply” only, so I can still use hot water without any issues. The filter is also very compact and doesn’t take up much space under the sink. The filter has a long service life of 16,000 gallons or 24 months, which means I don’t have to worry about replacing it frequently. The water tastes much better than before, and I feel more confident about drinking it. I also noticed that the water is clearer and has no sediment or particles.” — Yousef via Amazon
“I purchased this to use under the kitchen sink. It was installed by a plumber and worked for a few months. It began to continuously shut off when running cold water. Installed a new filter, and the same problem continues. My plumber says the filter is too small to use as I am using and it lacks enough flow rate. Before buying, compare the flow rate at gallons/minute to others. Moving to another brand with a flow rate of 2.5 gallons-per-minute.” — GG Texas via Amazon
Good for: Homeowners seeking a high-quality multi-stage filtration system available in multiple finish options.
What Are People Saying About the Aquasana 2-Stage Under Sink Water Filter System?
Our team found that customers who left positive reviews for this product liked that it had straightforward installation that required minimal tools. Others were impressed with its cost-saving capabilities and the impact it had on the taste of their water. However, there were a few customers who had issues with the filters not sealing properly and others who felt the flow rate was slower than they were anticipating.
“Installation was easier than expected, even with the added necessity of drilling a hole on the top deck of the sink to mount the dispenser […]Though the instructions suggest hiring a professional if drilling is required, we found it not to be a difficult task if you plan carefully, measure twice, and have good quality tools. After mounting the dispenser, the rest was relatively easy. The only hiccup was ensuring that the inlet and outlet hoses were firmly inserted all the way into the filter. Because the hoses are small, I was hesitant to push them as hard and deeply as you really must to get a tight seal. My first few efforts resulted in water spraying everywhere when the water line was opened. But after finally getting the lines properly seated, we haven’t had any problems since. Several months later, we’re still happy. It’s been well worth the initial expense and installation. —Amazon Customer via Amazon
“Overall seems like a solid product, but be prepared for slow flow rates. I suppose that probably means it’s doing its job, but there just isn’t sufficient surface area for the water to get through at any kind of reasonable rate. My house water pressure is set at 50 PSI, but I am only getting about a gallon every 2.5 minutes. Patience is required.” —Amazon Customer via Amazon
Best Two-Stage Water Filter
What Are People Saying About the FRIZZLIFE Under-Sink Water Filter?
Positive reviews our team found said that this under-sink water filter was well-packaged and easy to install and immediately improved their water’s flavor. Other reviews noted that its cartridge was easy to replace and reasonably priced. Negative reviews criticized this product for leaking and not being as durable as expected.
“This is my second Frizzlife as I recently moved into a new home. Installation was simple, and the water taste was clean and simple. I love how I can just purchase a replacement filter when needed, saving money, and it’s so much more eco-friendly. Highly recommend.” — MK via Amazon
“I wish I could provide a review on the taste of the water but all the provided metal fittings leak. With one wrap of Teflon tape on the metal fittings everything bottomed out and was unable to stop the flow of water. The plastic to metal was even worse, multiple wraps and bottomed-out fittings still leaked. It finally got to the point that I just gave up, took all the fittings out and put the filter on the shelf in the far back of the garage. I suppose the metal fittings would have worked if I had sweated them together, but that’s not the point of this kit. I originally bought this kit for the supposed ease of the provided fittings and the filtering.” —J.C. via Amazon
Good for: Customers seeking an easy-to-install system that can install on any cold water line. \
What Are People Saying About the Aquasana Under Sink Water Filter?
We found that customers who gave this product a positive review liked that it was well-built and durable, with several also noting that it greatly improved the water taste. However, there were others who felt that this filter was challenging to install, and others felt that it clogged too quickly.
“We had been using a Brita filter for the longest time but we got tired of constantly having to fill the container. This is a life changer. Not only it filters more stuff, you can just open the faucet and pour it immediately into your glass, pot, mug, or whatever. Installation was fairly simple, just annoying but got it in one try. I’d recommend this to anyone who doesn’t have a fridge with a water dispenser.” —F. Lara via Amazon
“It looks nice and is easy to install. Some of the parts are plastic, notably the plastic diverter, and you may want to replace them for peace of mind, if you’re worried about these breaking down. You’ll notice a drop in the flow rate of about 40 to 50%. It does a good job of filtering as you can taste the difference in the water. However, every three months or so you will have to replace a filter if you have a lot of sediment in your line. So you may still need a sediment filter upstream of this.” —Grimmy via Amazon
What Do You Need to Know When Buying an Under-Sink Water Filter?
When purchasing a water filter, it’s important to consider how its specifications and design impact its performance. Before deciding on an under-sink filter, it’s important to consider the unit’s filtration process, flow rate, and overall water pressure level. Read our buying guide below for more information on choosing the best under-sink water filter for your home.
What Are the Types of Filtration Process?
Most under-sink water filters purify the water supply through a carbon filter or reverse osmosis. Models with carbon filters purify water by absorbing contaminants. While carbon filters make under-sink water filters more affordable, they don’t remove all contaminants from well water.
Some under-sink water filters use reverse osmosis to filter water. Reverse osmosis water filters purify water by using pressure to force the water through a semipermeable membrane. This leaves behind volatile organic compounds, pharmaceuticals, and impurities in tap water, such as fluoride, heavy metals, herbicides, pesticides, and chloramine. While this is more effective than carbon, you can still get a quality carbon block filter, especially since most under-sink water filters use multiple layers of filtration to provide clean drinking water while leaving in healthy minerals like potassium, calcium, and magnesium.
Why Is Flow Rate Important?
An under-sink water filter’s flow rate is determined by how many gallons of water it can purify per minute. This number varies depending on the filter’s filtration method and size. For example, the FRIZZLIFE Under-Sink Water Filter filters two gallons per minute (GPM), while the more narrow Waterdrop Under-Sink Water Filter System filters 0.75 GPM.
How Does Water Pressure Affect Under-Sink Water Filter Performance?
An under-sink water filter’s water pressure impacts its filtration process, as low water pressure inhibits the filtration process. To ensure that their systems are operating at the proper water pressure, many models include water pressure gauges for easy monitoring.
Tips for Using an Under-Sink Water Filter
Using an under-sink water filter can help improve the quality and taste of your drinking water, but it’s important to understand how to use it properly to maintain water quality. Here are some tips for using an under-sink water filter:
- Shut Off the Water Supply: Before installing or replacing the filter cartridge, shut off the water supply to the filter system. This may involve turning off the water valve under the sink or at the main water supply.
- Flush the System: After installing a new filter cartridge or when first using the system, it’s essential to flush the filter. This helps remove any loose carbon fines or debris from the cartridge. Closely read the manufacturer’s instructions for flushing, which typically involves running water through the system for a specific duration or volume.
- Replace Cartridges Regularly: Under-sink water filters typically have replaceable cartridges that require periodic changing. Check the individual product description to see the recommended schedule for cartridge replacement. Regularly replacing the cartridges ensures that the filter continues to function effectively.
- Monitor Water Flow: It’s important to check the water flow rate after installing the filter. If you notice a significant decrease in water pressure, check the filter system for clogs or other issues. Some filters may require occasional cleaning or maintenance to optimize performance.
- Clean and Maintain the Filter: Periodically clean and maintain the filter system according to the product instructions. This may involve removing and cleaning components, such as the housing or diverter valve, to remove any sediment or build-up.
- Test Water Quality: Consider periodically testing your filtered water to ensure that the filter system is effectively removing contaminants. Home water testing kits or professional water testing services can help you assess the quality of your filtered water.
Undersink Water Filter FAQ
What’s the benefit of an under-sink water filter?
Under-sink water filters simplify water purification by filtering water at its source, removing the need to use water-filter pitchers and creating whole-house safe drinking water.
How much does an under-sink water filter cost?
The price of an under-sink water filter depends on a number of factors, including its filtration method and size. However, most filtration water systems cost between $50 and $100.
How long does the cartridge in an under-sink water filter last?
Most under-sink water filters require a replacement cartridge every six to eight months of use.
How We Selected the Best Under-Sink Water Filters
To provide our readers with the best recommendations possible, we rely on several key sources of information to help guide our selection process.
Initial Research: Our research process began by generating a list of under-sink filters with a significant number of verified-buyer reviews and an average customer review rating of 4–5 stars. We looked at positive and negative reviews alike, focusing on information from both satisfied and critical buyers.
Expert Insights: Through our years of experience, we’ve learned that listening to what others have to say is key to building accurate, well-rounded articles. To complement our in-house expertise, our team looked at reviews and videos from trusted publications and independent testers, spoke with subject matter experts, and drew insights from reader contributions.
Final Product Selection: We then began fine-tuning our list by replacing older models with the latest versions and eliminating any discontinued models. From there, we pared the list down further by comparing each model’s feature set and selecting the best-in-class options for a variety of buyers, budgets, and scenarios.
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