Most consumers in the United States opt for a water filter pitcher when they just need simple filtration in the kitchen. While we are big fans of pitchers, they can wear you out if you’re family consumes a considerable amount of water each day.
The best under sink water filter can address that issue, and you may be surprised by what they can remove. Whether you need an affordable in-line filter for the bathroom or a 3-stage unit for your kitchen, our guide will help you find the right option for your home.
What is an Under Sink Water Filter?
An under sink water filter is the next step up from a filtered fridge pitcher, but still a rung below most whole-house systems. They are designed for one tap and usually installed in a kitchen, although some under the counter water filters are ideal for bathrooms as well.
These small systems are perfect for consumers with municipal water that are in need of a simple POU system for a room in your home. What they can remove or reduce depends on what’s in the canister, but there are models that can deal with anything from chlorine to bacteria. An under the sink water filter does not work with hot water, however, and it is not the best option if you’re dealing with well water or serious contamination.
Under Sink Water Filter Buying Guide
Any system designed to slide under your sink is simple, and something you won’t need a professional to install. With that in mind, there are still several areas you’ll need to consider, but it all comes down to the type of system you choose.
Direct Connect or Multi-Stage Filter?
Does your sink have a knock-out hole in the top, or is it ceramic and freestanding? The type of sink you have can directly impact what type of under sink water filter you should buy. While there aren’t many variants, there are two styles to consider with multi-stage and in-line filters that connect directly to your waterline.
Multi-Stage:
An under sink filter system with more than one filter is considered multi-stage, and they are the most popular option for a reason. Those extra filters allow you to block more common contaminants including heavy metals and cysts.
Systems in this class usually have 2 to 4 filters, and most are rated for between 6 months to a year. On the downside, these filters divert water, so they come with a separate faucet which isn’t ideal if you don’t have a knockout hole. They also filter water much slower than our next option.
Direct Connect:
Any filter we label as direct connect or in-line are all single filter systems that essentially just screw onto your waterline. The filter can have multiple stages inside the canister, and they all have an excellent flow rate.
This style is generally cheaper, but, they may need changed more often considering they filter all your cold water. They also don’t block quite as many contaminants or do so at a slightly lower percentage due to the flow rate.
What contaminants do you need to remove?
We’re not going to spend much time here as an under sink water filter is limited with what it can remove. As mentioned, this type of filtration system is best suited for consumers that live in the city with a clean water supply flowing into their home, not someone looking for a filter for their cabin that uses well water. An under counter filter is built to handle common tap water contaminants, not exotic particulates or untreated water.
Chlorine and lead are the two most common contaminants an under sink filter can remove. They can also handle VOCs, herbicides, pesticides, and sediment to a degree as well. The easiest way to find out what type of filter system you need is to check the water quality report for your region. To find those numbers, you can pick up a CCR or Consumer Confidence Report on the EPA’s site or have your water tested by an independent lab.
Flow Rate & Pressure
There aren’t many technical specifications you need to know when dealing with an under sink water filter. Every manufacturer will list a PSI rate, which lets you know how pressure your sink has to have for the filter to work properly. It’s generally in the 25 to 35 PSI range, which is not an issue for most folks in North America. If you do have low flow, pay close attention to the next spec.
The main specification to keep an eye out for outside of filtration is the flow rate. It’s measured in gallons per minute and listed as GPM. While there’s no perfect number, the higher the rate, the quicker you’ll get a glass or jug of filtered water. A lower flow rate isn’t bad; however, as it can often mean the filtration is better considering the water spends more time passing through the filters.
Ease of Use
The term “under sink” is broad in the sense that sinks are different sizes, and the cabinets beneath them are different sizes as well. In fact, some sinks don’t have a cabinet at all, which is something to think about if you need a filter for your bathroom and have a pedestal sink.
All these factors come into play with ease of use. If you buy a larger 4-stage filter and have a cramped cabinet, you’ll want to take measurements beforehand. If filters are going to be a hassle to change, you don’t want to do it every few months, so also consider the filter life.
None of the systems on our list are hard to install, but some have a few more creature comforts which make life easier. How good is your memory? Unless your filtration system has a built-in reminder system, you’ll need to rely on your brain or a calendar for filter changes. Systems with twist-lock filters and push fittings are a joy to use and own as well.
Filtration
When it comes to the filters, you obviously want to consider what’s in them. That dictates the types of contaminants they can reduce, but there are only a handful of options for these types of systems, and most will use a form of carbon. It could be a carbon block, coconut carbon or GAC, but rest assured, if it’s built to block chlorine, it will use carbon.
KDF is another popular option in some multi-stage systems and direct connect filters. You can even find an under sink water filter with reverse osmosis although that’s something that would be considered overkill as a POU system for most homeowners. Regardless of what’s in the filters, consider how much it costs to replace them when their lifespan is up.
Certifications
Any device that comes in contact with food or water should have a safety rating, but that isn’t always the case. With water filtration devices, that comes into play with the filter along with tubing or any other parts that come in contact with your H2O.
While the governing bodies can vary around the globe, in the United States, we defer to the NSF Institute and NSF/ANSI standards. Companies that make water filters can have their products tested, listed and certified by the National Sanitation Foundation. Each system or filter can have multiple certificates, but the “phrasing” used by manufacturers is what you’ll want to look for.
A company can comply with NSF standards, but that doesn’t mean they were tested. When you see terms like “manufactured” or “tested to” NSF requirements, take it with a dose of salt. When a company claims their product has been “certified” by the NSF or WQA, that’s a different story, and you can trust that those products live up to the hype.
If a product doesn’t have proper certification, that doesn’t mean it’s bad as we’ve seen plenty of filters with stellar reviews and thrilled consumers that are not fully certified. If you want to check a product you have your eye on or double-check a company’s claim, use this tool from the NSF.
Image Product
Aquasana Max Flow AQ-5300+
- Flow Rate: 0.72 GPM
- Lifespan: 800 gallons
Editor's Pick
Culligan US-EZ-4
- Flow Rate: 0.50 GPM
- Lifespan: 500 gallons
Filtrete Maximum
- Flow Rate: 1.5 GPM
- Lifespan: 1500 gallons
Brondell Coral UC300
- Flow Rate: 0.50 GPM
- Lifespan: 600 gallons
Kube Advanced
- Flow Rate: 1.25 GPM
- Lifespan: 1600 gallons
iSpring CU-A4
- Flow Rate: 0.56 GPM
- Lifespan: 6 - 12 months
The Best Under Sink Water Filters
Our picks for the best under sink water filters consist of systems that use between 1 to 4 filters. We’ve included a price point and style for everyone, and if you become torn between two models, we’ve listed all the important tech specs and features which may help make your decision easier.
1. Aquasana Max Flow AQ-5300+ Under Sink Water Filter
The Best Under Sink Water Filter Overall
When you’re looking to reduce chlorine in your tap water and keep pesticides out of your food, the Aquasana Max Flow AQ-5300+ is an excellent choice. This system looks good below and above your sink, and as it’s been thoroughly tested, it is guaranteed to perform as advertised.
The AS-5300+ is a traditional 3-stage system with a filter set which sits below the sink, and a faucet you’ll need to install on top. While there are several features that set this one apart, it all starts with the filtration and the company’s Claryum technology. This particular set is geared to handle 800 gallons before you need to replace them and can reduce 97% of chlorine and 99% of lead.
The first stage handles sediment, while the activated and catalytic carbon filters take care of 61 other contaminants. You’ll need at least 20 PSI to make use of this system, but will be thrilled to know it’s fully NSF/ANSI certified to standards 42, 53, 401 and P473. The flow rate is also very respectable at 0.72 gallons per minute.
While the Aquasana AS-5300+ works like most of the other filtration systems on our list, there is one significant difference. In place of the typical reminder system, you get Bluetooth connectivity. This allows you to connect with an app to get detailed information on your system along with handy replacement reminders for the filters.
Consumers found this system easy to install, and the streamlined design won’t take up much space at 12.8”H x 4.2”W x 12”D. Replacements filters are reasonably priced for a set and are rated for 6 months. The Aquasana AS-5300+ comes with a 1-year warranty and is available in Brushed Nickel, Oil Rubbed Bronze or Chrome.
2. Culligan US-EZ-4 Undersink Filter System
The Best Budget Under Sink Filter System
Under sink water filters may all work in the same fashion, but how they are designed can have an impact on their performance. Culligan proves that with their EZ Change Undersink systems, and the EZ-4 is an ideal option if you’re tight on space or just want something simple.
The first thing we want to talk about with this under sink filter is its size. It’s smaller than a multi-stage system at 4”H x 9”W x 13.7”D but still a bit larger than in-line filters. It should slide under any cabinet with ease, and as it’s Culligan, it has been tested and certified by NSF to standards 42 and 53. It also has a ball and check valve built-in to the head along with an LED light to let you know when it’s time for a filter change.
As for that filter, it is capable of reducing sediment, lead, Class 1 particulates, cysts, mercury and VOCs along with Chlorine. That carbon block provides 99% lead reduction and 98% for chlorine. If your filtration needs differ down the line, you’ll be thrilled to know the EZ Change system works with a few different filters from the company as well.
The system has a flow rate of 0.5 GPM and requires at least 30 PSI to function properly. The filter is rated for 500 gallons or 6 months, whichever comes first. That lifespan is average for most under sink systems, and the replacements are fairly priced in comparison to the packs sold for multi-stage systems. That’s for the “Premium” filter, however, as there are a few more options available.
The Culligan EZ Change Under Sink system is available in three options depending on your needs although the EZ-4 provides the best bang for your buck and filters more contaminants than the rest. With that in mind, the EZ-1 is half the price and the best option for chlorine if you just need to improve the taste and odor of your water. All systems come with a complete install kit and a 2-year warranty.
3. Filtrete Maximum Under Sink Water Filter
The Best In-Line Under Sink Water Filter
Filtrete is a brand many consumers may be familiar with, but not for reasons related to water filtration. This 3M-based company is more known for their popular air filters although they made our list with their Filtrete Under Sink Water Filtration System.
Looks are deceiving with this filter. The 3US-MAXis capable of reducing 97% of chlorine from your water, but can also deal with 99% of microbial cysts and lead. A 0.5-micron sediment filter will remove sediment, rust, sand, and soil as well. That’s impressive and comparable to systems that have three filters instead of one, but the Filtrete Max has a much higher flow rate.
You’ll get 1.5 gallons per minute with this filter installed, and hooking it up won’t take long thanks to push fittings, a sturdy bracket and a handful of screws. The filter is rated for 6 months with a 1,500-gallon capacity. While you’ll need to remember to change this one out like all in-line filters, the company does provide a text reminder service.
3M has ensured this filter is safe as it has been tested by NSF, it’s certified for NSF/ANSI 42 and 53. While there’s not much to this system, it does have a 1-year warranty. If you aren’t concerned about lead and want to save a few bucks, the company also sells this kit with Advanced and Standard filters, both of which are interchangeable with this system.
4. Brondell Coral UC300 Under Counter Water Filter
An Affordable 3-Stage System from Brondell
Brondell isn’t your typical manufacturer. They carry a variety of home goods, including heated toilet seats, air purifiers, and water filtration products. Our top pick from the company is the Coral UC300, a simple system that’s extremely effective.
Do you need to remove lead and chlorine from your tap water? If so, the Brondell Coral UC300 will certainly do the trick. It can remove 99.7% of lead and 98% chlorine as long as you have at least 35 PSI to work with. Obviously, it’s not the best option for well water or fluoride, but it can handle general contaminants like VOCs, Cysts, Mercury, and Asbestos.
As you’d expect, the filters on this system use a twisting mechanism to make filter changes a breeze. The included faucet is chrome with a modern look and features an LED light at the base. That lets you know when it’s time to change the filter, but you won’t see it go off all that often. The filters in this set are rated for 600 gallons or 12 months, whichever comes first.
The filter set for this system includes sediment, pre-carbon, and carbon block filters. It’s a Gold Seal certified as well and was independently tested by the WQA. That means it’s certified to NSF/ANSI standards 42, 53, and 371 along with CSA B483.1. The UC300 under sink filter has an average flow rate of 0.50 gallons per minute.
If you live in a home with older pipes or deal with over-chlorination, the Brondell Coral UC300 should be at the top of your list. The company is known for making top-notch products, and this one ticks off all the important boxes when it comes to water filtration systems. We also appreciate the cost of replacement filters and its overall size. The UC300 is backed by a 1-year warranty from Brondell.
5. Kube Advanced Water Filtration System
A Streamlined System from Kinetico
If you are in the market for a unique faucet-less under sink filter, you’ll be hard-pressed to beat this one from the minds at Kinetico. The Kube Advanced Water Filtration system is the sleekest filter on our list, and it has an excellent flow rate along with canisters that can remove common contaminants.
Under sink water filters are generally not sleek, which is one reason they are kept under the sink and out of sight. Well, the Kube14 bucks that trend by allowing you to insert filters horizontally into a special housing. The system is narrow and neat at only 6” wide and 13” high but is 18.5” deep so you may need to check your cabinet depth or you could be forced to turn it sideways.
The filters use a twist and lock mechanism which makes filter changes a breeze, and there’s even a bypass knob in case you need unfiltered water and don’t want to turn off the tap. A filter reminder lets you know when you’ll need to change cartridges, and you can expect around 1600 gallons of filtered water before that time comes.
We don’t have a great deal of information on what’s inside the filters on the Kube, but we do know what they remove. That would be 99% of lead and chlorine, two contaminants found in municipal water supplies across the U.S. As mentioned, the flow rate is excellent on this system, so you can expect a rate of around 1.25 gallons per minute.
The Kube has been tested and certified by the WQA to meet NSF/ANSI standards 42, 53, and 372. It does require 35 PSI to function at full speed but comes with a 2-year warranty. We didn’t find any major complaints on this model although it is more expensive than similar models with a bit more filtration power.
6. iSpring CU-A4 Compact Under Sink Water Filter
The Best Under Sink Filter for Lead & Bacteria
Two and three-stage under sink water filters are by far the most common, but sometimes an extra filter can make a world of difference. That’s the case with the iSpring CU-A4, a system that remains compact while providing you with four stages of filtration.
123Filter’s water system is designed for ease of use. Everything is color-coded, and the filters simply twist on and off when it’s time for a replacement. At 13.5”H x 15”W x 4”D it’s par with other under counter filters on our list – just a little wider. It only requires 20 PSI to function as well while the flow rate clocks in at 0.56 gallons per minute. It’s not the quickest, but it’s far from slow considering it has four filters.
Wondering what that extra filter brings to the table? Well, it’s an 0.1mm Ultra-Fine Membrane which covers algae, bacteria and a slew of other harmful microbes. There’s a 5-micron polypropylene sediment filter before that, and a filter full of KDF and GAC that follows. It fights back against heavy metals while the last stage is activated coconut shell carbon.
In all, you’ll see a 99% reduction in chlorine, lead, and bacteria. Iron sees a 95% reduction rate, and the system as a whole filters out countless VOCs and fine particulates you’d rather not ingest. It will definitely improve the taste and odor. There’s no alert system for filter changes, but they all need replaced every 6 months aside from the UF membrane which is good for one year.
The iSpring CU-A4 comes with an air gap faucet and sports a 1-year warranty with a lifetime of technical support. The filters, tubing, and any parts that come into contact with water are “manufactured” to comply with NSF/ANSI and FDA standards, but not certified from what we can tell. That’s something to keep in mind although it’s hard to argue with the price tag and wealth of positive reviews.
Best Under Sink Water Filters Comparison
| Product | Filters | Dimensions | Lifespan | Flow Rate |
|---|---|---|---|---|
| Aquasana Max Flow AQ-5300+ | 3 | 4 x 12 x 13" | 800 gallons | 0.72 GPM |
| Culligan US-EZ-4 | 1 | 14 x 9 x 9" | 500 gallons | 0.50 GPM |
| Filtrete Maximum | 1 | 4 x 4 x 14" | 1,500 gallons | 1.5 GPM |
| Brondell Coral UC300 | 3 | 23 x 4 x 35" | 600 gallons | 0.50 GPM |
| Kube Advanced | 2 | 10 x 18 x 14" | 1600 gallons | 1.25 GPM |
| iSpring CU-A4 | 4 | 10 x 5 x 13" | 6 – 12 months | 0.56 GPM |
Final Thoughts
The best under sink water filter certainly won’t break the bank, and they can save you a great deal of money compared to a pitcher. While our picks are the best option for your kitchen or bathroom, some contaminants are tougher than others, so keep a whole house filter or RO system in mind if you live off the grid or rely on water outside the range of treatment plants.