Which Water Filter Removes the Most Contaminants?

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If you’ve recently learned about the hundreds of trace contaminants that drinking water contains, it’s unsurprising if you’re keen to drink filtered water from this moment on.

But when there are so many water filters and water purification systems to choose from, settling on a single system can be tricky.

Which water filters remove bacteria? Which filters remove chlorine? Is it better to buy an under-sink water filter system, a whole home filter, a faucet filter, or a water filter pitcher? Which filters remove the most impurities?

This guide should answer some of your most pressing questions in your search for the most capable water filter system.


Reverse osmosis systems and water distillers remove the most contaminants – however these systems may not always be the best fit for every situation.

🤔 Why Might you Need a Water Filter?

There are several reasons why you might need a water filter.

Even if you get your water from a municipal supplier, it still contains a range of trace contaminants, from metals to chemicals and other contaminants. You can check your supplier’s water quality report to see exactly what your water contains.

You might want to get a water filter to improve water taste. You might be more concerned about removing chemical contaminants that affect your health, or you might simply want to stay safe from potential water pollution or contamination issues in your local area.

Unfiltered water quality is much poorer than the quality of filtered water. Drinking filtered water is safer and better for your health.

⚙️ How do Water Filters Work?

Different types of water filters work differently. For instance, a reverse osmosis water filter uses a more unique filtration process compared to a carbon-based system.

However, the general concept of water filtration is the same: water flows through a filter media or cartridge, which targets and removes specific contaminants.

The complexity of filtration depends on the system you buy. A five-stage filtration system will likely target more contaminants than a single-stage filter.

Some filter systems also purify water, removing all impurities the water contains.

contaminants being removed by water filter

🔎 Which Types of Filters are Good at Removing Contaminants?

There are lots of different types of filters available on today’s market, and some are better at removing contaminants than others. Some of the most reliable filters for contaminant removal are:

Activated Carbon Filters

Carbon filters are made from materials that are naturally high in carbon, such as coal or coconut shell. Activated carbon filters are very porous, and can adsorb contaminants like chlorine and heavy metals in water.

In the adsorption process, large contaminants are trapped in the media’s pores, while the carbon media grabs onto the small impurities, preventing them from passing any further through the filter.

Activated carbon filter cartridges require a relatively long contact time between water and the filter media, which allows the filter to remove the most contaminants possible.

There are several types of activated carbon filter cartridges: granular activated carbon (or GAC), which consists of loose carbon particles; carbon block, which consists of blocks of compressed carbon; and catalytic carbon, which is a modified version of activated carbon that can remove sulfur.

Solid Carbon Block vs granular activated carbon Filters

Some of the filter systems that use an activated carbon filter are:

  • Under-sink filters
  • Reverse osmosis filters
  • Water filter pitcher models

The contaminants removed by an activated carbon filter are:

  • Volatile organic compounds (VOCs)
  • Organic chemicals, such as chlorine taste and odor
  • Some heavy metals (like lead)
  • Trihalomethanes (THMs)
  • Pesticides & herbicides
  • PFOS (perfluorooctanesulfonic acid)
  • Pharmaceuticals

Activated carbon filter cartridges typically have a lifespan of around 3 to 6 months, depending on the quality and size of the filter, the number of harmful contaminants in your drinking water, and how much water you use on a daily basis.

Related Article: Do charcoal filters remove lead?

Sediment Filters

Sediment filters are most commonly used for removing large contaminants from well water. As the name suggests, sediment filters remove particles of sediment from water, including sand, silt, dust, and rust. Sediment particles don’t have to be physical grains that we can see – they’re just bigger than most invisible contaminants.

You can buy sediment filters as standalone filters for whole-home filtration. However, many multi-stage filters, such as reverse osmosis filters and whole home filters, use sediment filters to protect the later filter stages from damaging particles.

There are two types of sediment filters you’re most likely to come across today: cartridge filters, which use layers of filter media to trap sediment smaller than a certain size; and spin-down sediment filters, which collect sediment and can be flushed periodically to extend their lifespan.

sediment water filter

Some of the filter systems that use sediment filters are:

  • Whole home water filters
  • RO systems
  • Ion exchange systems
  • Some under-sink filter systems

The contaminants removed by sediment filters are:

  • Rust
  • Sand
  • Dust
  • Dirt
  • Some heavy metals
  • Minerals
  • Organic particles

Sediment filters have a typical lifespan of between 6 and 12 months, depending on the type of filter and the quantity of sediment in your tap water.

KDF Filters

KDF Media

KDF filter media is made from high-purity copper-zinc granules, which produce a redox reaction – either reduction or oxidation – to reduce or remove a range of water contaminants. The KDF filtration process is certified to NSF Standard 61, and sees impurities converted into harmless forms, which are removed by backwashing.

The chemical reaction procured by KDF redox removes impurities like chlorine, heavy metals, and hydrogen sulfide. However, there are several types of KDF media, and not all media types remove the same contaminants.

Some of the filter systems that use KDF media are:

  • Whole home water filters
  • Well water filters
  • Faucet filters
  • Showerhead filters

The contaminants removed by KDF filters are:

  • Heavy metals (KDF-55 or KDF-C coarse mesh)
  • Sulfur (KDF-85)
  • Iron (KDF-85)
  • Bacteria (KDF-85)
  • Chlorine (KDF-C coarse mesh)

KDF media uses backwashing to flush the filter out. While this process does waste some water, it gives the media a much longer lifespan of around 6 years.

Reverse Osmosis Filters

Reverse osmosis (RO) filters consist of several filter stages, including a sediment filter, a carbon filter, a semipermeable membrane, and a post-filter. The unique feature of a reverse osmosis filter system is the semipermeable membrane, which consists of tiny pores and allows only tap water particles to pass through. This makes RO one of the most effective filtration methods available.

Membrane Filtration Process

A reverse osmosis system can remove the majority of total dissolved solids from gallons of water, including minerals, salts, microbiological impurities, organic compounds, and heavy metals.

Some RO filters use a remineralization filter to introduce healthy minerals back into drinking water, giving it a more enjoyable flavor.

RO filters come in three system types:

  • Under-sink water filters
  • Countertop filters
  • Whole-home filters (less common)

RO removes more than 100 trace contaminants from water, including:

  • Heavy metals
  • Radionuclides
  • Chemicals (chlorine, pesticides, herbicides)
  • Cysts
  • Fluoride
  • Some pharmaceuticals
  • Hardness minerals
  • VOCs
  • Sediment

There are several filters in an RO water filtration system, each with its own filter replacement schedule. Carbon cartridges have a lifespan of around 6 months, while sediment filters last up to 12 months, and the semi-permeable membrane lasts up to 2 years.


A distiller isn’t technically a filtration system – it’s a purification system that eliminates contaminants from drinking water. Distillers remove contaminants by evaporating and condensing water. Most contaminants are unable to evaporate at the same temperature as water, so they’re left behind in the boiling chamber, while water condenses into a separate container.

countertop water distiller

Distillation removes the majority of contaminants from water, but the distillation process can take a really long time. It takes up to 6 hours for a distiller to produce one or two gallons of water. Distillers also require electricity to operate.

The only feasible distiller for home use is a countertop unit.

Distillers remove the same selection of contaminants as RO:

  • Heavy metals
  • Radionuclides
  • Chemicals (chlorine, pesticides, herbicides)
  • Cysts
  • Fluoride
  • Some pharmaceuticals
  • Hardness minerals
  • VOCs
  • Sediment

Distillers use a no-filter process, but some distillers use an optional cartridge filter at the spout, which has a lifespan of around 6 weeks.

🥇 The Best Water Filter for Contaminant Removal

If you’re looking for the most capable water filter system for removing a range of contaminants, reverse osmosis and distillers are joint winners. These water filters produce purified water – water that contains no impurities whatsoever.

Reverse osmosis and distiller

💵 How to Invest Wisely in a Water Filter

Just because a water filter is one of the filter types listed above, it doesn’t guarantee that the filter is the best investment for you. Getting a filter that removes the most contaminants is great, but not all filters offer the same quality of performance.

To make sure you buy a water filtration system that’s the best value for your money, consider the following things:

Is the Filter NSF Certified?

An NSF certification is the biggest indication that a water filter removes the contaminants it’s advertised to remove. NSF International is an independent certification organization that tests and inspects water treatment systems.

NSF testing is rigorous, and only the top-performing filters are awarded an NSF certification. If a filter is NSF certified for removing a specific contaminant or set of contaminants, you can trust its performance.

What’s the Filter’s Lifespan?

The second most important aspect of a water filter’s performance, after its contaminant removal abilities, is its lifespan. The lifespan of a filter determines how long you can use the filter for before the cartridge or media needs to be replaced.

The long-term costs and responsibilities associated with owning a water filter depend on filter lifespan. The longer the filter lasts, the less frequently you’ll need to pay to replace the filter.

Most cartridge filters have a lifespan of 3-6 months. Filter media lasts much longer: whole home tank-based filters have a media lifespan of around 6 years.

Consider how much maintenance you’d prefer to do, and work out your maximum preferred annual spend for a water filter. This will help you to narrow down your choices to those within your maintenance requirements.

Which Contaminants do you Need to Remove?

Instead of looking for a water filter that removes the most contaminants, consider filters that remove the contaminants you’re dealing with.

Get your water tested to find out what it contains. If you have a specific problem – such as chlorine, heavy metals, organic compounds, or bacteria – you can look at filtration systems that will remove these contaminants.

tap score example report
Tap Score water test report

Many people are tempted by reverse osmosis systems because of just how many contaminants they can remove. However, RO water can taste fairly flat and flavorless because it lacks healthy minerals that contribute to water’s alkaline taste.

Does the Filter have a Warranty?

A warranty is a sign that the manufacturer has confidence in the durability and longevity of a water filter. If a water filter doesn’t have a warranty, ask yourself why. A lack of warranty suggests that the system is liable to break or become faulty, and the manufacturer doesn’t want to lose money sending out replacements.

Look for water filters with at least a 2-year warranty. This means you’re covered for up to 2 years if the filter experiences problems that don’t result from poor handling. The more expensive the filter’s upfront cost, the higher the warranty you should be looking at. Some whole home water filtration systems have limited lifetime warranties, which is good, because you’re spending thousands of dollars upfront.

What do Customers Think about a Filter?

Customer feedback and reviews are essential to understanding how a water filtration system lives up to expectations with everyday use. I recommend looking at two types of reviews: impartial long-form reviews written by industry experts, and customer reviews on the manufacturer’s website (or, if the product is sold on a marketplace like Amazon, look there).

Impartial long-form reviews can provide you with the information you need to make a decision about a product. Manufacturers aren’t always clear with their marketing, and what sounds like the best filter in the world might actually be no better than the rest. Impartial reviews will compare the product to its competition and let you know whether it’s a worthy contender.

Customer reviews are reviews from people who have bought a water filter, likely for similar reasons as you. Read these reviews to find out whether people are happy with the filter on the whole, and whether there are any problems that several people have experienced with the filter. This can help to separate the manufacturer’s claims from the reality of owning the system.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

2 thoughts on “Which Water Filter Removes the Most Contaminants?”

  1. Avatar for Jennifer Byrd

    I am looking for a water filter that gets rid of the helicobacter pylori bacteria out of the water from tap water,even though municipality treated.

    1. Avatar for Jennifer Byrd

      In most cases, helicobacter pylori should not be an issue in municipally treated water. Treatment facilities are legally required to add enough disinfection chemical that there is a residual in the water as it flows through the distribution system & protecting it from pathogens.

      That said, if you are still concerned, or want to be protected in the case of a boil water notice, I’d recommend installing a UV disinfection system

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