What Is a Water Filter? Why You Must Use One in 2024

Updated on:
February 28, 2024

If you’re here, you’ve finally realized that you’ve been drinking contaminated water and you want to do something about it.

My friend, you’ve been living under a rock. It’s about time you get out and experience all this modern world has to offer—yes, including water filters!

You’ve come to the right place. My mission is to stuff as much knowledge about water filtration in your head as possible so you can invest in a perfect filter and enjoy only clean and delicious drinking water from now on.

Let’s get started. 

What Is a Water Filter?

In simple terms, a device that cleans out any impurities in water is called a water filter. Now you might wonder what you should consider an impurity. Anything that is not H2O is an impurity. Some impurities are actually healthy, like minerals and vitamins, while others are plain devastating, like lead and arsenic.

A water filter will make your water clean and drinkable by removing bacteria, fine particles of sediment, inorganic materials, and even unpleasant tastes. If your water is not filtered, you’re basically consuming a dangerous mixture of contaminants that can even cause cancer! Sorry to scare you, but it’s the truth. 

Luckily, there are plenty of filters designed to remove one or a combination of contaminants in water.

From bacteria and viruses to minerals and radioactive metals, water filters can remove all the contaminants and make your water supply cleaner and fresher than spring water.

Not all water filters are created equal, though. Water filters clean water to different extents. For example, a cheap water pitcher will only clean dirt particles, while an expensive water distiller will literally remove every impurity.

You can go for point-of-entry (placed near the main water supply) or point-of-use (placed at faucets and taps) filters of different shapes and sizes. And you can filter your water through various treatment techniques depending on your water quality goals.

You’ll find a gazillion options if you decide to buy one today. After reading this article, though, you won’t be as confused as you probably are right now.

The Importance of Water Filtration Systems

Before I explain the types of filters and how they clean water, let’s talk a little about why it is so important for you to invest in one.

Why should you filter municipal water?

I’ll be honest with you, the water you get from the public water system is not as clean as you think. The same goes for the water in your private well.

You might argue that municipal and commercial water filtration zaps all the bad stuff in the water, but you forget the old and contaminated pipes that supply this water to your house.

These facilities are mostly located at the edge of the town, and water has to travel a long distance before reaching your taps. Many types of contaminants accumulate in the corners and crevices of the feed lines. Metallic pipes can corrode and leach lead and copper ions. Plus, the soil around the pipeline may contain dozens of microbes, pesticides, and chemicals.

If you think only feed lines are the problem, you’re wrong. Chemical treatments of city water can also leave fatal impurities in the water. 

Do you sometimes smell chlorine in your water? Multiple authorities perform shock chlorination to kill bacteria and viruses in water. But the smell of chlorine lingers, along with some dangerous by-products formed when chlorine reacts with organic matter and biological contaminants. These by-products are called trihalomethanes and are deadly enough to cause cancer. (When I mentioned cancer, I really wasn’t kidding.)

You must already know that fluoride is purposely added to city water across the US. Although fluoride improves dental health, too much of it can cause bone, thyroid, and some neurological disorders. You may need to filter it out.

Why should you filter private well water?

Private wells are traditionally known for producing high-quality drinking water. Hold on, this isn’t your cue to start digging one for yourself. 

Groundwater aquifers are frequently polluted with hazardous chemicals from unmindful human activities, such as unregulated industrial waste disposal, underground fuel tanks, failed septic systems, and the use of fertilizers and pesticides. There’s no longer a guarantee that water in wells will always be safe to drink. Pollutants like bacteria, lead, arsenic, nitrate, radionuclides, and toxic chemicals from various industries can easily seep through cracks and loose wellheads if your well is old or shallow.

It is absolutely necessary to filter water before using it, no matter what source you’re getting it from. Without one, you’re only hurting yourself and your family.

Some other downsides of not filtering your water

It’s not just about drinking water quality.Trust me, you don’t want to wash your laundry and body with water that’s full of chemicals, toxins, and minerals. 

Hard water from mineral contaminants will make your skin dry and super flaky, and you’ll lose that luster in your hair that you’re so proud of. It can also make cleaning your clothes and linens more difficult, since detergent won’t lather properly and mineral deposits can make your fabrics look dull and dingy.

Unfiltered water full of iron and manganese can leave orange and black spots all over your clothes. Those shiny white tiles and fixtures you just installed in your bathroom will turn yellow. Would you like to start your mornings by scraping off the brown scale in the bathtub? I’m guessing not.

I’m not done yet. 

Unfiltered water can clog and reduce the life of your pipes and appliances. Moreover, blocked pipes will disrupt the water pressure around your whole house. This can even increase your water and energy costs. With so much scale building up in every fixture in your home, you’ll be forced to put the maintenance guy’s phone number in your speed dial.

Additionally, water filtration can save you money on water! If you’ve been getting your drinking water from another source to avoid the contaminated water coming from your tap, you’re probably paying a lot for it, whether you’re having it delivered or buying bottled water. And don’t even get me started on the environmental consequences of bottled water.

Are you convinced enough to buy a filter now? It’s time to learn about the types of filters so you can pick the best one for your house. Buckle up.

The Most Popular Water Filtration Technologies

You may find yourself dealing with different types of pollutants that can only be removed through a combination of filters.

If you learn how each technology works and what it can remove, you can make an informed decision.

Ion exchange

Let’s start with the most popular filter type—ion exchange. 

Ion-exchange filters, as the name suggests, exchange unwanted ions, and in some cases potentially dangerous ions, in the water with more desirable ions. All water softeners are based on this technology. 

If your tap water doesn’t lather your hand soap well or if you feel dry and itchy after a shower, you probably have lots of calcium and magnesium in your water, and an ion-exchange water softener is what you need.

Ion exchange has a porous resin bed of sodium (or potassium in some designs) ions. When water passes through it, the metallic ions swap with sodium ions. Simple as that. 

Once the bed gets saturated with metallic impurities, this filter flushes all the nasty ions down the drain and replenishes itself with fresh sodium ions.

Ion-exchange filters will cost you anywhere between $400 and $800. If you want a fancier unit that backwashes and regenerates itself automatically and can be controlled from your smartphone, you’ll need to jack up your budget to around $1,000.

What does ion-exchange filtration remove?

Ion exchange uses two types of resin beds: cationic and anionic. Cationic exchange can remove manganese, iron, magnesium and calcium ions. While anionic resin beds knock out arsenic, fluoride, chlorides, sulfates, nitrates, and uranium.

The ion-exchange filtration process can’t remove bacteria, viruses, and other organic particles that have no charge.

Carbon filtration

A carbon filter will make all the nasty odors and weird tastes in your water go away like magic. You’ll find it in two designs: granular-activated carbon and carbon block. Granular-activated carbon is made of coconut shells or powdered coal and works by trapping chemicals in the filter. Block filters use much finer carbon powder to filter out more contaminants. 

Activated carbon filters are easy on the pocket and will cost you $50–$500. Carbon block filters, though, are on the higher end and can cost as much as $800.

Carbon filters require frequent replacement depending on the impurities in question and, of course, the quality of the unit. An average one will set you back $50–$70. 

What does carbon filtration remove?

The carbon filtration process removes chlorine, chlorine by-products, hydrogen sulfide (the reason behind that rotten egg smell in taps), pesticides, herbicides, and pharmaceutical residues.

It can’t remove biological contaminants like microbes and pathogens, fluoride, arsenic, and other heavy metals from water.

Chemical injection

Chemical injection systems inject a specific amount of disinfectant into the water at optimum temperature and pressure. This is a widely used method to remove microbial contamination in water. It’s cheaper than the rest of the methods on this list and would cost you around $300–$800. However, if you don’t want to invest in a dedicated injection unit for water disinfection, you can always perform shock chlorination in your private well using household liquid bleach for as low as $100.

The effectiveness of this method largely depends on the concentration of disinfectant, such as chlorine and hydrogen peroxide, contact time, and the pH of water. 

There’s one caveat though: chlorine can form harmful by-products by reacting with organic matter. You may need to combine it with an activated carbon filter to tackle the chlorine by-products.

What does chemical injection remove?

Chlorination will kill disease-causing microorganisms in the water. In addition, chlorine can oxidize metals, such as iron and manganese, into insoluble precipitates that can be filtered out easily. 

UV treatment 

UV filters use UV light to fry the cell walls of bacteria, viruses, fungi, and other pathogens. UV light disturbs their DNA, so they can’t reproduce and attack your body. These poor microorganisms don’t stand a chance against the UV filter’s 254 nm (nanometers) wavelength radiations.

Because of its fancy equipment, the UV treatment filter is slightly expensive and costs $500–$1,500. But you’ll get healthy water, free of those ugly microbes (you’d agree with me if you had the chance to see them under a microscope).

What does UV treatment remove?

Only the biological organisms in your water. Don’t expect UV filters to treat any other contaminants. In fact, you will have to install prefilters to remove solid particles and metal ions before the water passes through a UV filter. Otherwise, it won’t perform its job efficiently.

Air-injection oxidation

Another popular way of treating water full of metal ions is air-injection oxidation (AIO) filtration. This filtration method oxidizes metallic ions into solid metal oxides, which are later removed through mechanical filtration. The filter needs to be backwashed regularly to remove the captured metal particles.

AIO filters will cost you around $200–$1,500.

What does AIO remove?

AIO is best for removing iron, manganese, and sulfur. It will not trap chemical impurities, microorganisms, and other inorganic and organic contaminants.


If you want to taste the purest form of water, pay a visit to a nearby chemistry laboratory, or just install a distiller. But know that it won’t taste like anything because pure water has no taste of its own. Sorry to disappoint you. Minerals and electrolytes give water a fresh and soothing taste, and distillation removes them as well.

A distiller vaporizes water and condenses it back into a separate tank, leaving behind all that’s not H2O. This is also the reason why it’s the most expensive filter type. Distillation equipment will cost you $50–$4,000, with countertop units at the lower end and whole-house units on the higher end. Expect to spend $300–$500 on its installation, and don’t forget the additional ongoing cost of operating this high-energy filtration process.

What does distillation remove?

Distillation removes 100% of impurities in water, including healthy minerals and electrolytes. This water is squeaky clean but tastes flat.

If that’s an issue, you could always add salt, lemon, or mineral drops to your drinking water.

Reverse osmosis

Saving the best for last, reverse osmosis (RO) is easily the god of water filtration systems. It removes 99.9% of the impurities while keeping your water tasting fresh and delicious.

Reverse-osmosis systems combine different types of filters like sediment, carbon, and ionization filters to produce the ultimate in high-quality water. It’s a little pricey, but hey, this price tag is totally justified. In this day and age, the best kind of water comes with a cost.

These filters use a semipermeable membrane with a pore size as small as 0.0001 microns. Water is pushed through the filter membrane and stripped of all pollutants bigger than 0.0001 microns. This unit, combined with prefilters, removes all kinds of contaminants that give water an objectionable taste and smell, as well as those that pose a danger to human health.

The smaller units, like countertop and under-sink designs, run $250–$1,300, but if you want a whole-house reverse-osmosis unit, it’ll cost you around $4,000. Add $400–$500 to cover the maintenance and installation costs.

What does reverse osmosis remove?

An RO filtration system will remove bacteria, viruses, chlorine, sulfur, volatile organic compounds, heavy metals, fertilizers, and herbicides, to name but a few.

It leaves the water perfectly clean and healthy, devoid of all pollutants.

Types of Water Filter Designs

Now that I’ve covered filtration technologies let’s talk about the different designs of filters because every household has different needs.

Other than the types of contaminants in your water, your decision will be based on the amount of water used in the house, the space in your kitchen or basement, your lifestyle, and your budget.

On-counter/countertop filters

Countertop filters sit on the counter, right beside your kitchen tap. Their minimal and compact design will not invite too much attention and will deliver clean and clear water for just pennies on the dollar.

Countertop filters use different filtering technologies, like sub-micron filtration, ion exchange, activated carbon, and reverse osmosis to make your water drinkable. Depending on the filtering abilities and quality, these filters range from $70 to $500. They also come in many beautiful and dazzling designs to match your kitchen interior.

These units are super easy to install because they come pre-assembled. Just unpack the filter, grab a wrench, and give the instruction manual a read. You got this.

Under-sink filters

This design is especially for people (like me) who want their kitchen counters clean and tidy. Under-sink filters go under the sink and are easy to install and move to a different place if required.

They take up very little space and won’t cost you a fortune. Expect to spend around $300–$500 and an additional $100 if you are too lazy to install it yourself.

Faucet-mounted filters

If you don’t want to spend more than $100 on filtration, go for faucet-mounted units. These filters attach to the faucet ends and use carbon filters and semipermeable membranes to improve your drinking water. You can switch between filtered and unfiltered water easily.

Its cost-effectiveness makes it a great option if you want clean water on demand from multiple taps in your kitchen and bathrooms. Moreover, they typically last longer than an average water pitcher. And if you’re a little handy, you can easily install them yourself.

Water filter pitchers

Another inexpensive water filtration filter is a water pitcher. It can clean a few liters of water at a time and typically uses carbon filters and porous membranes to banish over 300 contaminants in water. 

Water pitchers will cost you between $20 and $200 and require regular filter replacement.

They take about 15–20 minutes to filter one batch. If you’re impatient, this is not for you.

Whole-house units

The whole-house unit—also called a point-of-entry system—will treat all the water entering your residence. These filters, although expensive, not only clean all the impurities but also extend the life of your pipes and appliances by preventing clogging. With whole-house filters in place, you can shower in clean water and drink healthily from every tap of your home.

Whole-house filters come with one to six filtration stages, depending on the size you opt for. The combination of sediment, carbon, UV, and reverse-osmosis filters makes your water squeaky clean and fresh.

It’s a bit heavy on the pocket and costs around $2,000, but it’s worth every penny.

How to Select a Water Filter for Your Home

If it’s your first time buying a water filter, I can totally understand your hesitation. Adulting is hard. Don’t worry, I’ll try to make it easier for you. Take notes or click a screenshot of this portion on your screen so you can revisit this checklist whenever you go shopping or search online for a water filter.

Start by learning about the quality of your tap water. You can demand an annual water quality report from your local water supplier. This report compares the concentration of toxins in your water with the standards set by the US Environmental Protection Agency. 

Get your water tested, either at home or in an accredited laboratory. From those results, follow these steps to get the best water purification system for your home:

  1. Find the filtration technology that can treat the contaminants you have in your water. 
  2. Now measure the amount of water you use on a daily basis. No need to do in-depth calculations. If you live alone or have a small family, you can go for water pitchers, tap attachments, countertop filters, or under-sink filters. If you have a big family, look for whole-house water filters.
  3. Check your wallet. Your budget will narrow down a lot of options. UV filters, distillers, and reverse-osmosis units cost more than sediment filters, carbon filters, ion exchange, and chlorine injectors.
  4. Last, don’t forget to cross-check the selected filter unit on the NSF database. NSF is a third-party organization that certifies water filters. This step is just to learn more about what the filter is designed to remove in your water, so you can verify the manufacturer’s claims and steer clear of misleading advertisements.

Final Thoughts

With ever-increasing pollution and decreasing water quality, installing a water filter is the need of the hour if you want to live a healthy and happy life.

To make sure you buy the best water purification system for your home, I have reviewed and compared the most popular types of water filtration technologies. You now know how each filter works, the type of impurities they remove, how much the filters cost, and which will be the best for your needs. Oh, and you know all about the different designs you can choose from.

Congrats! You’re now a walking encyclopedia of water filters. But wait, not so fast. After reading this detailed guide, you still need to learn how to install the filters you buy. Why call the plumber when you can install it yourself?

I hope from this day onward, you’ll only sip on the best, purest water and help others improve their lives as well. Until next time!

if you’re interested in learning about the terms often used in the drinking water industry, check out our Glossary page. Our glossary page provides a comprehensive list of commonly used terms in the drinking water industry, ensuring that you have a clear understanding of the terminology.

Whether you’re a professional working in the field or simply curious about the intricacies of water treatment and distribution, this resource will be invaluable in enhancing your knowledge.

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