How Do Water Filters Work? (Details and Explanation) in 2024

How water filters work depends, in part, on what kind of filter you are using. There are currently two primary categories of filters widely used, for either personal or commercial use.

Two Primary Methods of Filtration

Physical Barrier Filters

This pushes water through a semipermeable membrane that removes large particles. Think of how a coffee filter works.

features of physical barrier filters

Physical barrier filters remove things like:

  • Mercury
  • Lead
  • Dirt
  • Rust
  • Any particle that is larger than 0.001 microns.

Physical barrier filters have seen a big push in the last few years. These are seen in portable options for both emergency preparedness kits as well as reusable bottles.

These water filters work by removing the contaminants that have an immediate impact. However, they do not typically filter small particle contaminants like pesticides and chlorine.

The most common and most efficient physical barrier filters are reverse osmosis filters that manage to eliminate 99.99% of all unwanted particles.

Chemical Barrier Filters

The second is chemical filtration. Do not be fooled, this does not mean it is adding chemicals to the water. Rather, it means it uses a simple chemical process to remove impurities from the water.

Activated charcoal and water softeners are great examples of how chemical water filters work.

On the lower end of the chemical filtration, options are what is known as ion filters. These are more commonly called water softeners. These use sodium ions and exchange them for magnesium and calcium ions.

While chemical barriers filters are good at removing some of the minerals that can damage household appliances, they do little to remove other contaminants.

Activated carbon filters, on the other hand, work to remove smaller particle contaminants like chlorine, fluoride, and some pesticides.

Combination Filters

Many filters today use a combination of physical and chemical barrier filtration. Think of your common activated charcoal filters. Most of these have some form of physical barrier present, then run the water through the activated charcoal to grab the smaller particles. It is the combination of filters that provide the best filtration for today’s water needs.

Distillation – Less Common Option

We should note one option for filtering less commonly used at the point of service is steam distillation. The idea behind steam distillation is that you boil water to create steam. Anything heavier than the steam is left in the original container holding the water. The steam travels up and is captured in another container where it condenses as it cools.

One of the problems with steam distillation is that it is not generally something you can do on-demand when you want to use the water. Further, some contaminants do not get filtered out because they either boil at a lower temperature than water or are lighter than steam.

So now that we have looked at the concept of how water filters work, let’s analyze in more detail the types of water filters available on the purifier market and how each serves its purpose.

Gravity Filters

Gravity filters do exactly what they say, use gravity to filter water. Actually, gravity does not filter the water directly, but they use gravity to pull water through a filter.

Gravity filters can be both physical barriers as well as chemical barrier styles, depending on which one you purchase. The absolute best combine both styles, like the Brita Jug Filter.

Brita Water Filter Jugs

This particular filter uses gravity to draw water down through the filter and into the waiting jug. These particular filters actually use a combination of both physical and chemical barriers.

First is a physical barrier that helps to both collect large particles from the water. It also keeps black flecks from washing back into the jug as the water flows through.

Those black flecks would come from the activated charcoal that forms the rest of the filter. As the water flows through the charcoal it draws chemicals like chlorine out, leaving you with a better tasting and healthier glass of water.

These filters collect pollutants and therefore need to be replaced regularly. The regular white filters will typically filter about 40 gallons. For most users, this will last about a month. There is also a longer-lasting filter available, which filters roughly 120 gallons, or about six months.

types of water filters

There are many other forms of gravity filters you can try from a host of different companies. As you look for the right option, you want to look at what they filter out, and to what level. Be sure to look for third-party testing to validate filtration claims.

Refrigerator Filters

Most modern refrigerators with a water dispenser and ice maker have some form of filter built right into them. But how do refrigerator or ice maker water filters work, and are they better than the gravity filters?

This question is not an easy one to answer because, like everything we have discussed, it depends on a few things.

First, what kind of water do you have, and what are your primary concerns? Second, what kind of filter are you using on your fridge, and what is it designed to do?

Built-In Filters

Most people who are looking at refrigerator filters either already have a refrigerator with a filter or are considering purchasing one. These are the easiest to handle because they are already part of the system. You generally do not need to worry about leaking if you use the proper filter.

There are many options, though, when it is time to replace your filter. You can get filters with better capabilities, or just something less expensive. Either way, you want to be careful because a bad fit will mean leaking and possible damage to your fridge or floor.

You also want to be careful about any improvement to the filtering because of the difference in pressure as the water flows through the filter. The wrong amount of pressure can lead to additional leaking issues.

External In-Line Filters

Another option that has grown in popularity is the after-market in-line filters. These attach to the water line before it goes into the refrigerator.

Like any other filter, there is a wide variety of options available, with different capabilities. One thing that attracts a lot of attention to these filters is the low price point on some models. While the price may seem good, be sure to read reviews and third-party testing reports for how well the filter works.

Regardless of whether your filter is built into your refrigerator or it is somewhere in the waterline, you need to plan to replace it regularly to reap the benefits you are seeking. Be sure to read the details on the specific filter you are using to know how often you should plan to replace it.

Well Water Filters

Anyone with a well knows how challenging it is to get good water. Whether you are dealing with foul-smelling water or stains from extra minerals, it can be disgusting. Having a good filter is important and having the right filters for a well will give you the best quality.

If you have a well, you need a whole house filtering system. This will ensure your water does not destroy your appliances, toilets, tubs, or sinks. Plus, it will make sure your water is good and tastes great. How a well water filter works is a little different than if you are on municipal water because of the considerations of what you need to filter.

Sediment Filter

The first filter you want to look for is a sediment filter. Wells are notorious for bringing up dirt and grime. The very first step is getting rid of all of the visible contaminants in the water. This gives you clean and mostly clear water, but that is about all.

Mineral & Heavy Metal Filtering

Next is getting rid of extra minerals and heavy metals. Depending on what is in your water table, you may have egg smelling water or it may stain things orange. You may also experience extra buildup on your pipes, sinks, toilets, and other appliances. Other minerals and metal contaminants often go unnoticed.

water filter process

All of these issues can be caused by naturally occurring minerals and gases. Some of what you may have in your water includes:

  • Iron
  • Manganese
  • Calcium
  • Sulfide and sulfates from oil and gas deposits
  • Nitrogen
  • Silica
  • Arsenic
  • Chromium
  • Copper
  • Selenium

You may want to have your water tested to see what minerals your well contains. This will ensure you get the right filter for your particular situation.

A pollutant and Microbial Filter

The final filter you want to look at is something to filter out other pollutants and microbial contaminants.

Some of the other pollutants you should consider include:

  • Pesticides
  • Medications
  • Animal waste
  • Industrial contamination

In addition to these pollutants, you also want to consider the microbial contaminants. Some of the particular things you should consider filtering for include:

  • Salmonella
  • E. Coli
  • Campylobacter
  • Shigella
  • Cryptosporidium

Reverse Osmosis With Ultraviolet Purification

You may want to consider a reverse osmosis system if you have well water with a test showing high levels of contaminants. These systems can be for the entire house when installed in the primary water line. They can also be isolated to just consumable water if your primary concern is what you drink and cook with.

A reverse osmosis system typically has three to four different filters all working simultaneously. These include:

  • Sediment Prefilter: filtering large particles
  • Activated Carbon Prefilter: removing contaminants like chlorine
  • Semipermeable membrane filter: primary filtering of dissolved and smaller particle contaminants.
  • Postfilter: usually another carbon filter to remove any remaining contaminants and is not included in all systems.

In addition to the series of filters in a standard reverse osmosis system, there is also ultraviolet purification systems. These are a great addition for anyone who is concerned with biological contaminants like bacteria. The ultraviolet system renders these bacteria inert.

Finding the Right Solution for Your Situation

With all of these options, how do you determine the right solution for your home? First, consider what you need to accomplish. Do you need something for the entire system, or just for consumable water?

Second, know what is in your water. Do you need something to remove chlorine and fluoride from a municipal water system, or something more substantial? Consider testing your water so you know exactly what kind of filter you need.

Knowing what you have to work with for installation as well as the full annual operating expense will help you narrow down the options.

Finally, do the research. There are a lot of reviews of many different types of water filters and what they do. Look at both individual consumer reviews as well as third-party test data. This ensures you get the filtering you paid for once you do make your decision.