Water filters are devices that remove harmful or unwanted contaminants from water. Some filters remove many different contaminants at the same time, while others remove just one.
Filters are also designed differently to meet different needs. For example, some are permanent fixtures in your basement or under the sink, some are portable, some are pitchers, and others are attachments to your faucet.
All of this means that if you’re shopping for a filter, there are quite a few questions you need to answer first.
This guide will walk you through all the different types of water filters available on today’s market so you can be more informed and make the best purchase.
Filters for Different Water Sources
In general, there are two main categories of water filters: city water filters and well water filters.
They are different because different contaminants are found in each water supply. If you are looking for a water filter, the first thing you should do is confirm your water source.
Homeowners are likely to know their water source, especially if it’s a well. If you rent, you can ask the property owner.
Because well owners don’t pay for water from their own well, if you get a monthly water bill, you have city water.
City water filters
City water filters are specifically made to remove the contaminants that can be found in your water supply. Here are some of those contaminants:
- Chlorine and chloramine
- Industrial, agricultural, and pharmaceutical by-products
- PFAS, PFOA, PFOS, or so-called forever chemicals
- Volatile organic compounds (VOCs)
- Disinfection by-products (trihalomethanes)
- Haloacetic acids
- Heavy metals, such as lead, copper, nickel, chromium, etc.
City water supplies are made safe at treatment facilities according to the requirements of the Safe Drinking Water Act and EPA regulations. That doesn’t mean, however, that water from your municipal water treatment plant comes out of your tap 100% contaminant-free.
Among the contaminants municipal treatment plants can’t remove are pharmaceuticals, microplastics, and nitrates and nitrites. Water can also pick up contaminants after it leaves the treatment facility. For example, if your city or home uses older pipes made of copper or lead, these heavy metals can make it into your personal water supply even after leaving the treatment facility without them. Natural disasters, such as floods, can also cause mass-contamination at water treatment facilities.
All of this means it’s an excellent idea to filter your city water. Its potential contaminants can affect the smell and taste of your water, and some can even have short- and long-term health effects.
Well water filters
The other major type of water filters out there are well water filters. These are specifically designed for private wells. However, what this really means is that they are specifically designed for contaminants often found in wells. The main ones are iron, sulfur, and manganese.
But just because these are common does not mean they are in your well. Every well is unique and will have its own set of contaminants.
For example, if you live in an agricultural area, you might have high levels of fertilizers, herbicides, pesticides, or even microbial contamination from livestock waste. If you live near industrial sites, such as factories or manufacturing plants, your water may be contaminated with a number of dangerous substances, like chromium-6, lead, or arsenic. If you live in a coastal area, saltwater intrusion is common, which means your well gets contaminated by water from the sea.
Some contaminants are less from external causes and just from the local topography and geology. For example, tannins can also be found in some well water. Tannins result from the breakdown of organic matter, so they are common in forested or marshy areas. They aren’t dangerous, but they can give water an unappealing taste, color, and smell.
Another common well water issue is pH, the most common being acidic water, which has a low pH. Acidic water can corrode pipes and damage appliances, and it’s also not particularly healthy to drink. To make your acidic water safe for drinking, you may need to install a special filter that will adjust the pH.
Sediment is also very common in well water. Dirt, sand, clay, dust, and other particulates can make their way into your well and if not filtered can discolor your water and even affect taste, as well as damaging appliances.
All of this means that to find the right well water filter for you, the most important thing to do is to test your well water.
Only a lab water test will be able to tell you exactly what’s in your water, and then you can go out and get the filter that is most appropriate for your water supply.
Whole-House Water Filters
Beyond city versus well water, water filters are also divided by where within your home they filter the water.
First are whole-house water filters. As the name suggests, these filters supply filtered water to the entire home. You install them wherever the water supply line enters the house, usually in the basement or garage.
Whole-house filters incorporate a wide variety of filtration media, and they will differ depending on if you’re filtering well water or city water.
Installing whole-house water filters can be more difficult than their counterparts, point-of-use filters. It may be wise to hire a professional to help you, but this can increase the overall cost. The alternative is to learn how to install a whole-house filter yourself to see if you can save on installation costs.
They are typically more expensive up front than point-of-use filters, but they often are cheaper in the long run. This is because they are larger and include more filter media, which lasts longer and requires less frequent replacements.
However, the main benefit is that they provide clean, filtered water to every single tap in your home.
Point-of-Use Water Filters
If a water filter is not a whole-house filter, it’s a point-of-use filter.
These are different in that they only provide filtered water to one specific place. They are less expensive, less invasive, and often, though not always, more portable than whole-house water filters.
In the end, if you want a point-of-use filter, you need to first make sure it includes the correct filter media for your water supply.
If you’re on city water, this likely includes activated carbon and perhaps something else.
If you own a private well, the media needs to be able to remove what’s in your water supply.
After that, which point-of-use filter you use will depend on your specific needs and preferences:
Under-sink water filters
One of the more common types of point-of-use water filter is the under-sink filter, which is installed, as the name suggests, underneath your sink. The advantage of these filters is that they are compact, so they don’t take up much space, and they are also usually very easy to install.
The main disadvantage is they only provide filtered water to one part of your home, just like any other point-of-use system.
Under-sink water filters can be designed to remove a number of contaminants. The most popular and widely used filters feature activated carbon to remove chlorine and other chemicals commonly found in city water. The next most common include reverse osmosis, which uses a small membrane to remove heavy metals, salt, and other contaminants.
Faucet
A faucet water filter connects directly to your faucet and forces the water through a filter cartridge that usually contains activated carbon. These are relatively low-profile filters that will give you filtered water directly from your tap.
If you ever want unfiltered water, to use for cleaning for example, they come with a switch that allows you to bypass the filter and send water through the faucet like normal.
The downside of these filters is that they are small and usually only designed for city water.
You will also need to replace the filter cartridge regularly to maintain effectiveness, usually once every one to three months.
Countertop
Countertop water filters do exactly as the name suggests: sit on the counter.
They can come in two forms.
The first is as a stand-alone unit. Stand-alone countertop filters have their own water tank that you fill manually. They then dispense water after it passes through a filter inside the unit. The big advantage of these is that no plumbing is required, but the disadvantage is that you have to constantly refill the tank to have clean water.
The other type of countertop unit connects to your faucet. A tube then runs to the filter cartridge, which is housed in a plastic cylinder that sits on your counter.
From there, it runs through its own faucet, which you will install on your sink. It usually goes in the utility hole, i.e., where the sprayer goes.
The advantage of these is that you do not have to refill any tank but rather have a continuous supply of filtered water. The disadvantage is that the filter cartridge sits on your counter next to your sink and is somewhat unappealing visually.
Pitchers
Water filter pitchers are some of the most common water filters out there. They can typically hold between 0.5 and 1 gallon of water. To use them, you simply pour water from your tap into the top part of the pitcher. The water then runs through the filter and collects in the bottom half. When you need it, you simply pour it into a glass or bottle.
The big upside of water filter pitchers is that you can store filtered water for later use, either in the fridge or on the counter. They also work relatively fast and can give you filtered water when you need it. The biggest downsides are that you have to refill them frequently and the filter cartridges last for only one to three months.
Gravity filters
Gravity filters are designed with two separate compartments. Unfiltered water goes in the top compartment and then slowly drips down into the bottom compartment. It does this on its own thanks to gravity, and as it does it passes through a filter that removes contaminants.
These are excellent filters because they can remove a large number of contaminants. They also allow you to store large quantities (one to three gallons) of filtered water at a time and are portable. The drawback is that they take a very long time, sometimes multiple hours, to fill up with filtered water.
Portable filters
There are plenty of portable water filters that can be used outside the home and on the go. There are backpacking and camping water filters, filter straws, water bottle filters, and more.
These often include the same filter media as at-home filters but are designed to fit in a bag or your pocket.
Reverse Osmosis Filters
Reverse osmosis filters, also known as RO, are another type of filter that fall into their own category because they can be either whole-house or point-of-use. The vast majority are point of use, largely because the up-front cost and long-term maintenance costs of a whole-house reverse osmosis system can be quite high. But they do exist.
These filters work using a membrane with super small pores and water pressure. This pushes the water through the membrane, which then catches a wide range of contaminants. They are usually paired with sediment and activated carbon filters to maximize efficiency.
Reverse osmosis filters “produce” clean water by separating your existing water into clean and dirty supplies. Clean water is stored in a tank that is accessible to you via a dedicated faucet. However, tankless reverse osmosis systems do exist. These provide continuous water without a storage tank.
The big advantage of RO is that it’s a super effective filter capable of removing hundreds of different contaminants. The disadvantage is that it wastes water and can also break down easily if you don’t properly pre-filter the water.
Contaminant-Specific Filters
While many filters are designed to remove a range of contaminants, some things found in water need specific filters to remove them:
- Sediment filters: Sediment filters work like a screen to trap sand, dirt, clay, dust, etc. and remove it from your water. Sediment filters cannot remove chemicals, heavy metals, or microbes, aka bacteria and viruses. Typically, they are used only on well water because this is where sediment is most commonly found and because sediment in city water is removed at the treatment facility. But if you see sediment in your water, you may need to install a filter.
- Fluoride filters: Fluoride is found in both city and well water supplies and requires special filtration. Most fluoride filters use either activated alumina (aka aluminum oxide), which removes fluoride much like activated carbon removes chlorine, or reverse osmosis.
- Lead filters: A heavy metal, lead in the water supply can have serious long-term health effects, especially in children. Lead water filters require specific filter media and can be expensive. If you’re worried about lead in your water, it’s best to start with a water test to see if this type of filtration is needed.
- UV purifiers: Microbes in your water, such as bacteria, viruses, cysts, and parasites, can be extremely dangerous to your health, in both the short and long term. There are several ways to remove them, but UV purifiers are some of the most effective. They zap these organisms with a high-intensity UV light, which alters their DNA and kills them on the spot. They are not effective against any other type of contaminant and are usually featured as the final stage of a multistage filtration system that tackles a wide range of contaminants.
Water Filters for Specific Use Cases
Beyond well water or city water, whole house or point of use, and contaminant-specific water filters, there are many other devices you can use to purify your water:
Garden hose filter
Although also technically a point-of-use water filter, garden hose filters are specifically designed for outdoor use.
If you want to drink out of your garden hose, or you’re concerned about contaminants damaging your ornamental or edible plants, you can find options that use activated carbon or even KDF, much like you would find in a whole-house filter. Other options help remove hardness minerals, such as calcium or magnesium, to reduce streaks and stains on your driveway. Garden hose filters for wells will usually target iron or magnesium, which can also leave stains wherever you spray your water.
One thing to note is that if you install a whole-house filter correctly, meaning at a point between the main supply and your home, then your garden hose water will already be filtered. But installing a specific garden hose filter is a less expensive option if you don’t need or want to treat water in the rest of your home.
In-line water filters
In-line water filters fit directly into an existing water pipe and filter the water that passes through it. They are a good option thanks to their low-profile design and ease of installation.
One of the most common types of in-line filters are refrigerator in-line filters. Many modern refrigerators come with built-in ice and water dispensers. These are often welcomed conveniences, but only if the included filters are effective against the contaminants in your water.
In cases where they are not sufficient, you can install a separate in-line water filter. These attach to the water line that runs to your fridge and ensure that both the water and ice that come out of the dispenser are clean and safe to drink.
Water distillers
Water distillation is the process of boiling water until it’s in vapor form and then condensing it back into water. When this happens, impurities such as heavy metals and minerals are removed, leaving the water clean and safe to drink.
It’s a highly effective way of purifying water, but it’s a fairly expensive and energy-intensive process. Nonetheless, if you want water that is 99.99% pure, then distilled water may be for you. It’s possible to buy bottles of distilled water at grocery stores and pharmacies, or you can purchase a water distiller and make it at home.
Shower filters
Depending on what’s in your water, you may want to install a showerhead filter. The most common reason to do this is chlorine. If you have high levels of chlorine in your water, the steam that comes from your hot water can smell, and if the levels are high enough, it can even burn your eyes.
Shower filters allow you to remove these contaminants right there. But since most people don’t drink water from their showers, they are not as useful if you are trying to improve the quality of the water you consume.
Water Softeners
Another type of filter is one that few people consider a filter: a water softener.
These filters remove certain minerals and make hard water soft, as the name suggests. Hard water is the common name for water with high levels of calcium and magnesium.
While not harmful to your health, they can cause a wide range of problems around the home. The most common is ugly scale buildup on faucets and fixtures. More importantly, that scale buildup can affect your water-using appliances, even causing your heating elements to fail. Hard water also reacts with soap and prevents it from lathering, leaves streaks and stains on your plates and glasses, and causes skin and hair issues.
Water softeners are water filters that are specifically designed to remove calcium and magnesium. But you will never see them referred to as filters.
There are two types of water softeners: salt-based and salt-free. Salt-based water softeners use salt to initiate a chemical process that removes calcium and magnesium from water. Salt-free softeners are not actually softeners because they do not soften water. Instead, they convert calcium and magnesium to a different form that cannot form scale buildup. Salt-free “softeners” do not address any of the other issues of hard water.
Since water softeners only target calcium and magnesium, they are often sold alongside water filters as filter/softener combos. Such combinations help build a more complete water treatment system in your home.
Other Types of Water Treatment
Water filtration is one part of a larger science known as water treatment. This is the process of improving the quality of water for a specific purpose. If that purpose is removing things, then a filter or softener might be all you need. But there are other water treatment products designed to add things:
- Hydrogen water machines: These machines infuse water with hydrogen gas, which many believe to have powerful antioxidant and anti-inflammatory effects. The science behind this process has not fully proven this, but anecdotal evidence is promising.
- Alkaline water filters: Also often called water ionizers, these machines change the pH of your water so that it is alkaline, i.e., above 7 and not acidic. Proponents believe alkaline water is better for you and can improve overall health, though the science behind this is equally as uncertain as it is with hydrogen machines.
Finding the Right Water Filter for Your Needs
Once you’re ready to purchase a water filter, there are a few steps you should take. The first is to determine if you’re on well water or city water.
Then, you should test your water. This will tell you exactly what’s in your water and will make it much easier to choose which is the best water filter for your needs.
Finally, take a look at some water filter reviews to compare the different products out there and find the one that meets your specific needs and budget.
If you still need more information, either before or after you purchase a water filter, check out our numerous water filtration how-to guides. These cover everything from installation and filter replacements to routine maintenance and more.
