The Different Types of Under Sink Water Filters Explained

Author: Rory Mullan - Published: 2022/02/10 - Updated: 2022/11/22

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Relatively affordable and easy to maintain, under sink water filters offer a convenient way to remove water contaminants.

Besides, they last long and are an inexpensive alternative to bottled water.

On top of that, they fit seamlessly under your kitchen sink, avoiding the trouble of creating additional space on the countertop.

However, choosing from a wide range of under sink filters can get overwhelming. Thus, we’ll discuss several types to assist you in your buying decision.

So, here is our guide on the different types of under sink water filters.


  • For large, floating particles, sediment filters are the ideal choice.
  • Filters with activated carbon are great for a variety of contaminants (chemicals, heavy metals, etc.).
  • For water with chloramine, catalytic carbon should be used.
  • For water with water-soluble heavy metals and chlorine, use a KDF under sink water filter.
  • Iron, sulfur and manganese can be removed with the help of an oxidation filter.
  • For inorganic materials, use ion exchange filters.
  • For fluoride and arsenic filters, use filters with activated alumina.
  • To remove a broad variety of contaminants, consider reverse osmosis systems.
  • For microbial contamination, use UV water purifiers.

What’s an Under Sink Water Filter?

As the name suggests, under sink water filters get installed under the sink – could be bathroom or kitchen sink.

The water treatment solution comprises one or more filter stages and removes all or just a specific group of contaminants from your home drinking water, depending on what type of filter you’re using.

Generally, activated carbon is a common filter media found in under sink filters. Aside from that, some units also come with reverse osmosis membranes, ion exchange resin, sediment filter cartridges, catalytic carbon, KDF, etc.

A few homes with fewer contaminants in their water only need basic filters like sediment and carbon. However, those with more and harder to remove stuff might need additional filtration methods to purify their water optimally.

How Do the Different Types of Under Sink Water Filters Work?

Under Sink Water Filter Types Thumbnail

As stated earlier, you have the option to choose from multiple under sink water filter types. Every type differs from the next due to other filter media and therefore filtration methods used.

Naturally, different filter media types target different impurities/contaminants.

Other factors that make under sink water filtration systems differ from each other include installation and maintenance requirements, and cost.

If you’re planning to invest in an under sink filter, you may be interested to learn about all the types and how they operate. This will ultimately help you choose an appropriate one for treating those contaminants present in your own home water supply.

RO Systems

One of the most popular, advanced and effective water purification methods is reverse osmosis[1]. Most reverse osmosis systems are built to fit under your kitchen sink effortlessly.

That said, these systems are slightly different from standard water filter systems for two good reasons.

  1. They come with their own faucet and support a pressurized water tank.
  2. Second, they require a drain connection for flushing wastewater.

But what about contaminant removal? Fortunately, RO systems target all types of water impurities and pollutants, thanks to the different filter stages used. The RO membrane itself can trap particles as small as a thousandth of a micron.

Simply put, regardless of what your water holds, from pesticides to heavy metals, these systems can purify it.


  • RO systems greatly improve your water quality.
  • They offer a practical solution for treating severely contaminated water.
  • Reverse osmosis membranes do not need frequent replacements.


  • A few people report tasteless water after installing an RO system.
  • Slightly expensive to purchase and maintain.

Simple Under Sink Water Filters

Most single-stage under sink water filters use just one type of filter media. Though these filters can be pretty effective for water purification, their practicality depends on the exact filtration process.

However, regardless of which filter you decide to buy, you’ll get one at an affordable rate, and a little DIY work will help you install it. In other words, installation is straightforward and doesn’t require too much technical knowledge.

The main filter media used and techniques in single-stage filters include the following.


Granular activated carbon is the standard option when it comes to under sink water filters. It combines chemical reaction with adsorption in order to remove contaminants.

The material is highly porous.

Not only does activated carbon remove chemicals like chlorine and TTHMs, it also works to eliminate foul odor and unpleasant water taste.

In addition, GAC filters have high flow rates which is another plus.

Block Carbon

Manufacturers glue together extremely fine powdered carbon to create an emulsion when designing these filters. Then, the mixture is squeezed into a filter cartridge.

Aside from chemicals, most carbon block filters can eliminate cysts and bacteria from water due to having low micron ratings.

Sediment Filter

two water filter cartridges dropped in water

This is the most common type used in under sink water filters and for the right reasons. Whether your water contains sand, dust, rust or other dirt, sediment filters successfully trap all of them.

Depth, surface and absorptive filters are the main sub-types of sediment filters.

Just note that a sediment filter can handle a range of suspended particles in your water, but does not work against salts, chemicals, and other dissolved substances.


KDF filters help eliminate water contaminants through redox reactions.

They’re made of a copper-zinc alloy and can eliminate water impurities like lead, chlorine, mercury, chromium and hydrogen sulfide.

Besides, KDF also stops bacteria and other microbes from contaminating your water.

Catalytic Carbon Filter Media

Catalytic carbon is suited for eliminating hard-to-remove chemicals from a water supply.

Though standard activated carbon does not filter chloramine, catalytic carbon does.

So, if loads of chemicals in your water are a problem for you, make sure you purchase an under sink water filter with catalytic carbon filter cartridges.


We highly recommend activated alumina[2] if you want to eliminate arsenic or fluoride.

AA is pretty effective in targeting both.

Ion Exchange Resin

Ion exchange is yet another popular method to target contaminants lurking in home water supplies.

However, note that ion exchange resin only works for certain contaminant types. Therefore, they aren’t a practical solution for homeowners looking for functional filter media to treat overall water conditions.

Most ion exchange filter cartridges eliminate inorganic particles like sulfate and arsenic.

Iron Filter

Iron filters target one specific water contaminant: Iron.

They first convert soluble iron into insoluble rust. The filter media then traps the rust, giving you clean, fresh water.

UV Filters

A few under sink filters feature UV filter cartridges. They use ultraviolet light for water disinfection.

When the bulb emits the UV rays, the microorganisms in the water get inactivated. The rays destroy their DNA. As a result, they stop reproducing and cannot affect the health of anyone drinking them.

Under Sink Water Filters with 2 or More Stages

Under sink filtration systems with 2 or more filter stages treat your water more thoroughly.

They often use sediment cartridges at the beginning of the filter process. This prevents clogging of the other filter. The second stage typically consists of activated carbon to treat aesthetic water issues. KDF or ion exchange filter media for heavy metal removal might follow.

However, the process is not the same for all multi-stage filters.


  • These filters target a broad spectrum of water pollutants.
  • They combine several filtration techniques.


  • Installation is a bit harder.
  • Maintenance costs more than for other filters.

under sink water filter being installed

Separate Water Dispenser or Inline Design

Aside from the filter process, some under sink water filters use a separate water dispenser, while the others don’t. The latter are called inline filters.

Inline filters are installed with the existing water line in your kitchen. The filter starts working as soon as you open the kitchen faucet. So, before the water flows out of the tap, it gets filtered.

On the flip side, under sink water filters with a dedicated faucet only activate if you use said fixture. This saves filter capacity when you don’t need filtered water.

What’s the Average Lifespan of an Under Sink Water Filter?

Several factors determine the lifespan of under sink water filters. These include the filter type and your water conditions.

Generally, you need to replace filters yearly or biyearly. Nonetheless, if your water has a mad amount of sediments, you might need to replace more often.

Though a professional plumber can help you replace filters, you can easily do it yourself, too. Here’s how:

  1. Close the water supply and drain all the extra water.
  2. Get rid of the filter housings and dispose of the old cartridges.
  3. Clean the housings and install new cartridges.
  4. Re-install filter sumps.
  5. Check the water flow and also examine for leaks.

Frequently changing and maintaining filter cartridges will improve filtered water quality.

Are Under Sink Water Filters a Worthwhile Investment?

Under sink filters are inexpensive, easy to maintain, and beyond that, keep your water free from harmful contaminants.

The best part? They do not require you to make adjustments in your kitchen. Instead, they fit seamlessly under the sink and don’t take up much space.

After installing one, you would only need to spend some money on replacement filters, unlike bottled water which costs a lot more.

On top of that, if you purchase a quality unit, it will last for several years. Besides, drinking filtered water will save you medical bills.


Under sink water filters are effective for water filtration and can be hidden under a kitchen or bathroom sink.

The different under sink water filter types are simple, multi-stage and reverse osmosis.

Under sink water filters use their own dedicated faucet or the existing one.

6-12 months in their average life span.

Ease of installation and maintenance, and fair price tags make under sink water filters worthwhile.

Further Reading


Meet Rory Mullan

Rory Mullan Rory has joined the Water Masterz team as a contributing writer. He has covered all sorts of topics in the last several years.

Outside of his writing work, Rory enjoys photographing the Irish landscape and making music!

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