Water contamination is a serious issue that requires immediate action depending on its seriousness.

The build-up of bacteria, chemical contamination or harmful metals leaching into the water are the most common cases of water contamination that both filter manufacturers and, in some cases, homeowners are all too familiar with.

Sometimes, when the contamination level is higher, or the type of contamination is serious, single-stage water filters may not be efficient enough to remove all harmful chemicals from your water.

Therefore, they may not eliminate the possible health risks associated with using water that’s contaminated.

In many, this fact raises multiple questions like “How many stages should a water filter have in order efficiently remove contaminants lurking in water?” and “Is a multi-stage water filter better than other filters provided by water filter manufacturers?”.

What are Multi-Stage Filters?

When it comes to water filter systems, it is important to mention that each system is made up of water filter cartridges, each cartridge technically corresponding to a stage of the filtration.

Each cartridge in the filtration process has a specific role, targeting specific contamination issues.

Usually, there is a different filter material in each cartridge. However, the same type of cartridge can appear twice in the same system, but depending on their position in the system, they can have different roles.

Take reverse osmosis filtration systems, for example, which can feature two carbon block filters with the exact same capabilities.

Yet, the filter that’s placed upstream of the reverse osmosis membrane is a pre-filter that has the role of removing chemical contaminants that would damage the membrane filter, while the carbon block filter placed downstream of the membrane filter is a polishing filter that’s placed there to remove any residual chemicals. Polishing filters are also called postfilters.

Depending on the issue with your tap water, a single-stage or a multi-stage water filter can help you solve these issues.

Filters that integrate a single filter cartridge that contains a single type of filter media are called single-stage water filter systems.

The most common examples of this type of system include single-media countertop filters, inline filters or under-sink water filters. These usually remove taste and odour issues, chemical disinfectants and their by-products.

However, some water purity problems require water treatment systems with multi-stage filters. Multi-stage filters basically operate with multiple filter cartridges and each contains a different type of filter media. Reverse osmosis filters are the most typical example of a multi-stage filter system.


Are Mixed-Media Filters the Same as Multi-Stage Water Filters?

Mixed-media filters are water filters with a single cartridge that integrates multiple filter materials usually in layers.

They could technically still be considered multi-stage, yet filter systems made with multiple distinct cartridges offer a strictly stage-by-stage filtration that distinguishes itself from mixed-media filters because of the longer contact time and the larger surface area of the media in these filters.

Therefore, filters with cartridges that are each dedicated to a single type of filter material are more efficient because of the increased contact time of the filter material with water. Also, the filter material usually has a larger surface area, which translates to better adsorptive/contaminant rejection qualities.


What are the Advantages of Multi-Stage Water Filters?

Compared to other water filter systems, multi-stage filters have several advantages that make them a worthwhile purchase.

Let’s see what benefits these filters can guarantee and what are the disadvantages you should take into consideration before purchasing a multi-stage filter:




  • Thorough Filtration: The number of cartridges can be a good indicator of the efficiency and the level of filtration your water filter system can provide. By having multiple cartridges, each dealing with the specific part of the filtration process, this type of water filter can surely offer a trustworthy and thorough filtration.


  • Multiple Targets: A multi-stage water treatment solution has a higher capacity to remove harmful contaminants from your water. These filters target a wider range of dangerous substances. This means that by installing a quality multi-stage filter system you won’t have to worry about invisible chemicals and other contaminants adversely affecting your and your family’s health.




  • Flow Rate Reduction: Since multi-stage filters are using different filter cartridges in order to be more efficient, this can trigger a disadvantage regarding the flow rate. Having too many water filter cartridges in a system can potentially interfere with the desired flow rates. To avoid unpleasant surprises, check the specifications of the system for expected flow rates.


  • Increase in Maintenance Costs: Having too many cartridges in a filter system translates into an increase in the upkeep costs of your water filter system. So, when it comes to filters, the purchase price of the filter is not the only factor you should consider, maintenance cost is also important to keep in mind. However, contaminant removal efficiency should be the number one priority when buying a water filter system.


What are the Advantages of Mixed-Media Filters?

When it comes to the advantages of mixed-media filters, it is essential to mention that if you prefer to save money and space, buying one of this type of filters could be a great deal for you.


  • Better Flow Rates: When using a single filter cartridge, the risk of low flow rates shouldn’t have to worry you. Better flow rates are definitely guaranteed if you choose a single-cartridge mixed-media filter system.


  • Save Space: Having to accommodate a single filter cartridge helps you to save some space. For example, you can save some undersink space for other items. This means that the water filter system itself requires significantly less space in your home. Also, if case you prefer to store cartridges for later maintenance, you won’t need to sacrifice so much space from your storage room or any part of your home.


  • Save Money: From this point of view, when comparing mixed-media filters to multi-stage water filters, the difference is easy to spot: less cartridges to change, less money to spend on maintaining your water filter system.


How Many Stages of Filtration?

It depends. The level of contamination and the type of contaminants will usually determine what types of filter media can address your issues.

If we take the typical example of a reverse osmosis filter, then 5 stages are usually the minimum that these filters integrate (a sediment filter, a carbon block prefilter, a reverse osmosis membrane, a carbon block or granular activated carbon postfilter, and an alkaline filter).

It all depends on the efficiency of the filters and their contaminant removal rates. Therefore, you should check with your vendor for detailed information on contaminant type and contaminant removal rates.


Which One to Get?

Before making your decision about your future water system filter, make sure you are well-informed about your water and the issues you are dealing with.

To avoid surprises, contact your local water department, also don’t forget to get your water tested. This is the best way to find out what kind of problem you have and how serious is the contamination level in your water.

Testing your water is the main determining factor in deciding which type of water treatment your water requires.

Knowing about the differences between single-stage, multi-stage and mixed-media filters, your decision should focus on the contaminants you need to target.

Make sure you choose the right filter for the specific issue in your water.

If you want to make sure your home appliances are also protected, choose a filter with scale inhibiting properties as well.

Analyse and understand the advantages and disadvantages listed above and choose the best filter designed for your needs.


How to Test Your Water?

At-home water testing kits are the easiest way to test the quality of the water. Most are test strips that you must dip into water that you’ve collected from the tap.

Don’t expect all tests to tell you exactly how much of a specific contaminant is in your water. For the most part, they’ll only tell you whether a certain contaminant is present or not in your water.

While test strips are relatively cheap and easy to use, they may return false positives or negatives, and you may have to repeat a test to see if it returns a different result.

Any positive test should be followed up with a laboratory testing to see the level of contamination. Lab testing is more reliable than testing carried out with a dipstick.

For a lab testing, a representative may come to your home to take a sample, or you may be asked to collect the sample yourself and send it back to the lab.

You should test for contaminants by drawing water from your kitchen sink. The water should be collected from the “first draw”, which means first thing in the morning, after the water has been sitting undisturbed in the pipes all night.

Water from the first draw will tell you about the contaminants that may be leaching from your pipes. You may also be asked to take a sample after flushing your pipes by letting water run for about 30 seconds. This sample will tell you the contaminants leading to your building.

If you don’t have access to municipal water but a private water source, you will be asked to take a sample both from your tap and from the source itself.



The filter system you should get will depend on the contaminant types and levels detected in your water. A water treatment system that integrates multiple stages is preferable over single-stage units, even if these single-stage units contain a mixed-media filter.