Under-Sink Water Purifier Review

The best under-sink water purifiers deliver bottle-worthy tap water for a fraction of the cost. These systems use not one, but several filtration stages to remove contaminants that affect taste and smell.


Single-stage systems tend to reduce fewer contaminants than two-stage options that use reverse osmosis. Also consider the system’s water flow rate and how easy it is to replace filter cartridges.

1. Aquasana AQ-5300

This small, compact filter is a great choice for those who don’t want to invest in a large under sink water filtration system or for those who simply have no space to spare under their kitchen counter. It can reduce more contaminants than many other filters and still maintain healthy minerals like calcium and magnesium in your drinking water. It’s also very affordable when compared to other under sink water filtration systems, especially considering that it only requires biannual replacement filters.

This Aquasana under sink water filter, which is a 3-stage model (also known as the Aquasana Claryum 3 Stage Max Flow Under Sink Water Filter System), uses a pre-filter that traps rust, sediment, silt and other organic matter to extend the life of its second and third stages. These stages remove more than 77 different types of contaminants, from chlorine and chloramines to asbestos, pesticides, herbicides and lead. They can even remove living pathogens such as coliform bacteria, E. coli and other dangerous organisms.

Unlike other under sink water filters, this one does not require a plumber for installation and is relatively easy to hook up. Depending on your DIY skills, you should be able to complete the job in about an hour or less. Changing the filters is easy too, thanks to their covers which can be screwed off and on again or slid off and replaced within minutes. This under sink water filter system also comes with a battery alarm that will sound and show a red light when it’s time to change the filters.

2. Culligan RC-EZ-1

The Culligan EZ-1 Easy-Change drinking water filtration system is a good choice for consumers looking for an under sink water filter that’s simple to install, low in maintenance and provides clean, great tasting water. Its patented cartridge design removes sediments, bad taste and odors and chlorine from tap water. The EZ-1 can also reduce particulates class III. The system is NSF certified and backed by a 2-year limited manufacturer warranty. The package includes a filter head with built-in bracket, the RC-1 level 1 basic filter replacement cartridge and a filter change reminder sticker.

Installation is fairly straightforward if you follow the included detailed DIY instructions. The kit comes with a feed water adapter and tubing that connects to the inlet port of the filtration system. It’s important to note that this tubing needs to be installed a few inches away from the cold water line for proper operation. It’s also important to leave 1 1/2″ clearance under the faucet for cartridge replacements. Once the tubing is properly connected to the inlet port and the cold water line, it’s time to mount the unit. Start by placing a mark 5/8” from both ends of the unit’s mounting bolt and drill a hole accordingly. Once mounted, slide the plastic compression nut over the tubing followed by the ferrule and hand tighten the nut before snugging it with a wrench.

3. Aquasana AQ-5200

Unlike water filter pitchers, under-sink water filters provide more gallons of clean H2O in less time. But what’s more, they do it while retaining important minerals like calcium, magnesium, and potassium at permissible levels. The AQ-5200’s NSF certified Claryum filtration technology uses a scientific sequence of granular activated carbon, catalytic carbon, and ion-exchange to clear 88 contaminants including arsenic, chlorine, lead, PFOA, PFOS, and other heavy metals, while also reducing common chemicals such as herbicides and pesticides.

The system has a respectable 500-gallon capacity and a 0.5 gallon per minute flow rate, enough to keep up with the demands of most households. It’s worth noting, though, that this model doesn’t remove fluoride, so if you want to do that, consider the Aquasana’s big brother (the AQ-5300).

A small manufacturer’s box arrives with brass fittings, durable tubing, and a separate faucet that attaches to your sink. With a little DIY know-how, this Aquasana under-sink water filter should take about an hour to install. Just be sure to read the entire manual before you start, especially if you’re not familiar with plumbing work. It may also help to have a plumber nearby to do the water line connections. The AQ-5200’s filters have a lifespan of six months to a year, and the smart indicator light let’s you know when it’s time to change them.

4. Aquasana AQ-5100

The Aquasana AQ-5100 is one of the most popular under sink water filter systems available on the market. It does an excellent job of removing most contaminants from the water and its three different filters last up to a year each. The AQ-5100 is BPA free and uses high quality materials. It is easy to install and comes with a full instruction manual.

Unlike most other under sink water filter systems the Aquasana uses three separate filters rather than a single stage. The first filter is a 20-micron pre-filter that traps rust, silt and other sediment in the water. The second and third filters use ion exchange technology to remove chlorine, mercury, and other chemicals from the water. This system also has a built in bacteria removal feature which is important for many people.

One of the reasons the AQ-5100 did so well in the Consumer Reports lab tests was its ability to remove a wide variety of contaminants from the water without altering the taste, smell or other properties. Another nice feature is its ability to retain healthy minerals in the water which other filters like reverse osmosis and distillation do not.

The AQ-5100 is also very easy to install and you can usually do it without having to pay for a plumber. It comes with a mounting bracket, supply line, T-fitting, chrome tap, color coded tubing, and filter cartridges as well as an illustrated instruction manual. The installation process should not take more than an hour for most adults and can be done by yourself.