When it comes to drinking water, you want the best quality water possible.
Unfortunately, tap water is not always optimal and there can be many types of contaminants in it that we don’t want in our bodies. That’s why people install a water filter in their home or office.
But there are so many different kinds of water filters.
So how do you know which one to choose?
I bought my first water filter over seven years ago (I moved to Asia and the water quality was TERRIBLE!). Since then I’ve used, tested, reviewed, and researched every single type of water filter around.
This post will cover all of the different types of water filters, filtration methods, and form factors.
And we’ll explain the advantages and disadvantages of each to help you make an informed decision.
What is a water filter?
A water filter is a device that removes contaminants from the water.
Most types of water filters use some type of media or substances to aid in their filtration process: activated charcoal, carbon block, ion exchange resins or membranes (such as those made with cellulose), and reverse osmosis.
Water filters vary based on how they remove these impurities; whether it’s by trapping them via gravity, drawing them onto an absorbent material such as granular activated carbon, or removing dissolved solids through membrane processes like RO/DI units.
Types of water filtration
There are many types of water filters and each type is suited to particular kinds of water.
Sediment filters are designed to filter out larger dirt and dust particulates such as sand, silt, and rust.
This type of water filter is most often used as a pre-filter for well-water. A sediment pre-filter can protect the next stage of filtration from damage and extend its life.
They can be coarse or fine types of media, with the finer types being able to trap smaller contaminants. They’re usually made from sand or red brick (sometimes called “grit” – this type will need replacing annually).
If you’re noticing black sediment in your water, installing a sediment filter will probably be your first port of call.
Reverse Osmosis (RO)
A reverse osmosis water filtration system is a method of water purification for removing minerals, salts, chemicals, and particles from drinking water. The reverse osmosis process uses pressure to reverse the natural flow of liquids through semi-permeable membranes.
Reverse Osmosis (RO) can remove contaminants including lead, nitrates/nitrites, radium, chloramine, organic pollutants including trihalomethanes; bacteria, and cysts like cryptosporidium or giardia; pesticides and herbicides; and much more.
A reverse osmosis system can be quite expensive to install. They are also relatively expensive to operate. This is because reverse osmosis filters (membranes) usually need changing at least once a year. And even more often if you have bad water quality.
It’s a common misconception that reverse osmosis systems can cause cancer because it removes essential minerals. It’s been proven that reverse osmosis does not increase the risk of cancer as a balanced diet should provide these anyway. And it’s recommended by many doctors for people with kidney disease who need to stay on dialysis.
Activated Carbon Filters (AC)
AC filtration is most often used for removing chlorine tastes from tap water. It can also be used to remove heavy metals like lead and arsenic, pesticides, herbicides, volatile organic compounds (VOCs), and much more .
AC is porous so it’s able to trap contaminants efficiently. This kind of water filter lasts about six months to a year.
There are two different types.
Activated Carbon Blocks
A carbon block water filter is made by grinding activated carbon into a fine powder. This powder is then mixed with a binder and compressed into a solid block.
Activated carbon filter blocks are usually more expensive.
The ground carbon is much smaller than GAC, so they have more surface area and are more effective.
But they have a lower flow rate. This means they filter much slower.
Activated carbon blocks will also need replacing more frequently.
Granular Activated Carbon (GAC)
Granular activated carbon filters use powdered, loosely bound carbon to remove contaminants from drinking water.
GAC has less surface area to trap smaller contaminants, so they’re not as effective.
But they do have a longer lifespan than activated carbon blocks. They filter faster and are usually less expensive.
Distillation is another water purification method that can remove the most harmful chemicals and microorganisms from contaminated water.
It’s the only way to fully eliminate bacteria such as coliform, lead, arsenic, nitrates/nitrites, herbicides, or pesticides.
It uses heat in order to boil contaminated water, captures the steam that rises from this boiling process, cools down, and condenses it back into clean drinking water . The contaminants are left behind in the container where they were boiled because they don’t evaporate as steam does.
Distillation is not only used for drinking water. It also has uses in machinery, cleaning, home appliances, and even for fish tanks.
Distillation purifies water to the highest level. But it’s is an expensive process and requires a lot of energy as you need to boil the water.
Ion Exchange Filters
Ion exchange filters are often used for removing heavy metals, organic compounds, and microorganisms from contaminated water.
They use ion exchange resin that has positively charged hydrogen ions (H+) in it. This removes contaminants by attracting them with the same charge.
It also softens the water by removing sodium ions that make water hard to use in a home with appliances. This is because ion-exchange filters replace these sodium ions with potassium (K) or hydrogen.
Ion exchange is a simple process that doesn’t require any electricity or heat. But ion exchange resin is expensive to replace when it runs out.
Ultraviolet Disinfection (UV) filters
UV disinfection is a water purification method that can remove the most harmful chemicals and microorganisms from contaminated water .
This is done by using ultraviolet light to kill microorganisms in the water such as:
- E. coli
- Legionella bacteria
Producing ultraviolet light only removes living things, so therefore doesn’t remove harmful chemicals, metals, and other contaminants. So this technology is usually used in conjunction with other technology like activated carbon and reverse osmosis.
Take a look at our best UV filters article for more information.
Ultrafiltration  is a water filtration technology that is similar to Reverse Osmosis (RO) as it also uses a membrane.
The main difference between the two is that UF filters out particles that are larger than 1 nanometre in size while RO only filters particles greater than 5 nanometers in size. Ultrafiltration can remove more turbidity and contaminants than RO.
UF purifies water by using high pressure to force water through a very fine membrane. The pressure forces the water molecules through micron-sized pores in the membrane, but larger particles are too big to pass through and remain on one side of the membrane.
While UF is more effective than RO and doesn’t use energy to work, UF is more expensive to maintain. UF resin is expensive to replace, and as the UF membranes are thinner than RO membranes they have less lifespan too.
Activated alumina  can be an effective treatment method for source water with high total dissolved solids levels or sulfate concentrations.
Activated alumina cartridges contain granules that have an adsorptive surface that traps certain contaminants. As water passes through, the activated alumina granules absorb contaminants.
Regeneration is necessary for activated alumina cartridges, and this should be done regularly based on the number of gallons the manufacturer recommends. A professional should take charge of regeneration, as dangerous chemicals are produced.
Overall, activated alumina is uncommon in household systems and generally not recommended.
Ionization is a water treatment process that uses electrical charges to alter the chemical structures of contaminants. It’s also known as ‘electrolysis’.
Most ionization filtration systems have ionization as a second stage, usually after a carbon filter.
An ionizer splits filtered water into either alkaline or acid water. The acid water is discarded, and the alkaline water is used as drinking water.
It is still unknown if alkaline water – that’s been ionized by electrolysis- actually has any impact on human health.
These systems are also very expensive, and there is a lot of marketing hype surrounding ionized water. Some people have gone as far as calling alkaline water a hoax.
Greensand Iron Filtration
The greensand media has a coating of manganese oxide, which oxidizes iron and other elements in water when it touches it . The iron filter backwashes every few days (usually at a pre-sent time), thereby cleaning and restoring the media.
Greensand is often used in combination with other filtration methods and is usually installed as a whole house water filter. It’s suitable for high levels of iron.
Air injected iron filters
These water filtration systems use oxygen to remove iron and manganese from the water.
An air injection water filtration system typically has a venturi to induce air in front of the existing pressure tank. Once oxygen is in the waterline and then pushed through the pressure tank, iron and manganese can be oxidized.
Air injection filters are also effective for removing hydrogen sulfide, although they are not suitable for removing higher levels of iron.
Chemical Injection Iron Filters
Most commonly, this type of water filtration system uses chlorine to remove iron, bacteria, and hydrogen sulfide from well water. Although other chemicals are sometimes used.
A chemical feed pump injects chlorine into the water, which then causes a reaction with the iron to form rust.
Sediment filters can remove this rust after it is oxidized. Following this, a carbon filter is commonly used as the next stage to remove the extra chlorine that was introduced into the cycle.
Got iron contaminated water? Check out our post on the best water filters for iron well water.
The method has been around for centuries, and while it was one of the first types of drinking water filters to be used, ceramic filters are now less common.
The benefits are that most of these systems don’t use chemicals or electricity to operate – just gravity alone is enough for filtration. Although there are some under the sink or whole-house models that may require electricity to operate the pump .
Ceramic filters use tiny pores to trap bacteria and sediment in drinking water. So they’re quite good at removing bacteria, sediment, and turbidity. Ceramic filters with carbon are common, and this improves the filtering of VOCs and chlorine.
The best ceramic filters are an affordable and popular choice for drinking water filters. The initial cost is low, and they can be scrubbed and cleaned regularly to increase their lifespan.
Different Types of Water Filters for Your Home
There are types of water filters with form factors to suit different uses. Broadly speaking these can be divided into two categories.
A point-of-entry water filtration system is also known as a whole house filter. They filter water at its source, immediately as it enters the house.
Point-of-use water filters, filter tap water water just before you use or drink it. For example, a faucet-connected filter or a showerhead filter.
Whole House Filters
Point-of-entry (POE) systems are also known as whole house filters. They filter water at its source, immediately as the water supply enters the house.
You’ll usually install a whole house filter in the basement.
The advantage of a whole house water filter is that you don’t need to install multiple systems in each room of the house.
They can however be expensive and are nearly always more difficult to install. If your water supply is particularly bad quality then this is usually recommended.
Inline Water Filters
Inline water filters are often installed under the sink, or in line with your pipes.
They’re often used as a secondary water filter, or for purifying the cold water line for your refrigerator and ice maker.
Under Sink Water Filters
Under-sink water filters are actually a type of inline filter but they are most often used in the kitchen.
They need to be installed under your sink, and then you can attach a faucet diverter valve or replace an existing one with this filter.
They’re easier to install than whole-house water filtration systems and are best used when your only concern is drinking water.
Countertop Water Filter
A countertop water filter is installed on your kitchen counter.
Countertop filters are usually a point-of-use and they’re often used by the entire family or household for drinking water, cooking, and so forth.
Countertop water filters are most commonly ceramic, carbon block, or reverse osmosis systems. But others are used.
Water Filter Pitchers
A water filter pitcher is a type of point-of-use system that you can fill and then drink from. The most popular brands are Brita and PUR, but there are others.
They usually contain activated carbon filters, which make them an affordable option for filtering your tap water at home. They’re also usually good at removing fluoride, which is a worry for many people.
Alkaline pitchers are another popular type of pitcher, that aim to bring your pH levels as close to neutral as possible. Some people believe that pH-neutral water brings various health benefits.
The main downside to these types of systems is the need to refill them regularly with new batches of tap water. It’s easy to forget if you’re not in the routine.
Pitcher water filters also require more frequent replacement (usually every few months) than other countertop systems.
Another issue is that they’re not very effective at removing heavy metals or fluoride from the drinking water.
Despite the issues, water filter pitchers are one of the best ways to get started filtering water at home. And they can help you save a ton of money vs bottled water too.
Portable Personal Water Filters
These types of filters have grown in popularity in recent years.
Portable water filters are often used in the backcountry, during travel, or for emergency preparedness.
The filter is usually small and lightweight so it can be moved with you.
Some portable filters use a combination of ceramic and activated charcoal media to remove both taste, odor and chemical contaminants from water sources.
The disadvantage is that they’re not designed for daily use – the cartridges will need replacing every few days or so depending on how much you’ve used it
A shower head filter is installed on your shower head, and it works by filtering the water as you wash. Shower filters are point-of-use.
They’re easy to install and can usually filter chlorine, heavy metals, and other chemicals too. Some people believe that this improves the health of their skin and hair.
They are a good solution if you’re only looking to improve the quality of the water you wash in.
But if you have many bathrooms, you’ll need to install several of them. They also need changing quite frequently. So in some cases, whole house water filters may be a better option.
Water Filtration vs Water Softening: What is the difference?
Although they are often talked about interchangeably by many people, water softening and filtration are not the same.
Water softening is not a type of filtration – a process that removes calcium, magnesium, and other minerals from water. It’s done through a process known as ion exchange.
Ion exchange replaces the hard mineral ions with sodium to make the water less harsh-feeling on your skin and taste better
There are many benefits of installing a water softener in your home. Such as removing the hard minerals from your water so it improves its taste and smell. Hard minerals are very common in well water, so if your home has a well, see our post on the best softeners for well water here.
It also prevents scale buildup in pipes which can lead to clogs or leaks due to mineral deposits accumulating over time.
Having some trouble with your water softener? Head over to our post on common water softener problems and how to troubleshoot them.
Make the best choice for your home & drinking water needs
Hopefully, this post has helped you to understand what kind of water filtration is best for your family’s needs and lifestyle.
Water filters can save you a lot of money compared to bottled water. So it’s worth doing your research.
We recommend getting a professional water quality test done so that you can better determine which type of filter will work best for your household.
If you already know the kind of filtration you need, check out our reviews and buyer’s guides of the best water filters.