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Do I Need To Replace Filters on a Prescribed Schedule?

by Jennifer Bellini

Marketing expert, Business guru

> 2 min read

Do I Need To Replace Filters on a Prescribed Schedule?

Whether you own an activated carbon model or a reverse osmosis purification system, you’ll need to replace the filters regularly to ensure they continue doing an effective job of cleaning your household water supply. 

There are many types of water filters. Some use semi-permanent membranes to absorb contaminants in your supply, while others contain integrated carbon-based media layers. 

When considering how often you should change the cartridges or membrane in your water filter, you’ll need to take into account several factors, including the type of integrated media, the manufacturer’s specifications, and your household supply’s contamination level.



Standard Replacement Schedules for Different Types of Water Filters 

There are three main types of water filters, and each one has slightly different standards when it comes to replacing its built-in media. 

Activated carbon filters 

These filters work as absorption systems, with a built-in carbon-based media layer that traps contaminants like chlorine byproducts, industrial substances, organic compound chemicals, and various waterborne pathogens. There are several types of activated carbon filters, from those that use coconut shell media to those containing anthracite coal or mixed wood layers. 

Despite being effective at removing foul odors, tastes, and destructive microorganisms from your water supply, these types of filters also have their weaknesses. When water passes the carbon-based layer, the contaminant molecules stick to the surface of this medium. This creates an unpleasant coating known as adsorbate, and over time this film covers the pores and holes of the carbon, rendering your filter obsolete. 

If you use a charcoal water filter, you should aim to replace the cartridge every two months. If you have a filtration system that uses coconut shell media, you can wait around six months before replacing the cartridge with a new one. This form of carbon tends to have a lower pressure drop than charcoal, extending its lifespan. 

Reverse osmosis filters 

This type of filtration system uses an integrated semi-permeable membrane to filter and purify your household water supply. The contaminated water flows through the membrane, and this film catches the larger, harmful particles in the supply, like organic compound molecules, chloride, lead, chromium, and arsenic. The smaller water molecules pass through the membrane and out the other side, so you’re left with a clean supply. 

Reverse osmosis systems tend to contain several separate filters, including a pre-filter that catches larger sediment pieces and an activated carbon unit that removes chlorine and its disinfection byproducts from your water. Some RO models also have an integrated carbon block filter. 

You’ll need to change the carbon and sediment-based cartridges 2-3 times per year, but you can leave the semi-permeable membrane for longer. As a general rule, you should aim to change this absorbent layer every two years, but some manufacturers recommend replacing the membrane every 8-9 months. You want to ensure the membrane’s microscopic holes aren’t becoming congested with a buildup of insoluble particles and molecules: this will lead to a drop in your household’s water pressure. 

Mechanical filters 

Mechanical filters remove sediment particles, silt, scale, organic compound molecules, and other potentially harmful contaminants from your water supply. Some units contain mesh cartridges that catch larger particles of five microns and above, while others have integrated ceramic-based layers that can remove microorganisms as small as 0.5 microns. 

If your unit contains sediment or mesh cartridges, you won’t need to change the filter layer as often as you would with a device that uses condensed ceramic or fiber materials. That’s because these media contain much finer holes and pores, so they become clogged up more quickly than layers with looser, less compact structures. 

Check with your manufacturer for their recommendation on when you should change your filter’s cartridge. You may have to change the media layer for replacement filters every 2-3 weeks, depending on what it’s made from and how contaminated your water supply is. On the other hand, if your household supply is relatively clean and you’re using a sediment-based cartridge, you can replace the media layer every few months. 

Signs That You Should Change Your Water Filter Cartridges

If you’re not sure about when to replace your water filter media, you should look out for three key signs that the current cartridges have become ineffective. 

Your drinking water tastes or smells unpleasant 

If you notice a salty or metallic taste in your drinking water, this could be a sign that your filter media has become clogged or that your reverse osmosis system’s membrane has broken down. 

When these media layers decay or become congested, they can begin to let contaminants like mercury, lead, arsenic, and iron through the filtration system. These types of particles cause a bitter taste in your tap water. 

If your activated carbon filter has developed a coating of adsorbate, this can lead to the media layer releasing various contaminants from the film to make room for new ones coming in. These contaminants may include chlorine molecules, which flow back into your water supply and give your tap water a disinfectant-type flavor. 

When chemicals like chlorine, hydrogen sulfide, and molecules of biological matter flow through your old, ineffective filters and remain in your household supply, you’ll find that your drinking water emits a particularly unpleasant odor. Hydrogen sulfide creates a rotten egg smell, while chlorine produces a bleach-like aroma. These are all signs that you should change or clean your cartridges. 

You’re experiencing drops in household water pressure

If you are experiencing sudden and drastic drops in the household’s water pressure, this may also indicate that there’s something wrong with your water filter. 

When your filter’s sediment-based media layer becomes clogged up with contaminants and organic molecules, this can slow down the purification rate and decrease the flow of your supply. 

If you want to raise your system’s pressure again, try replacing the filter cartridge. You could also look into getting a sediment-based media layer that targets larger molecules: these tend to remain effective much longer than filters with lower micron ratings. 

Your water looks turbid and murky 

Another simple way to tell if it’s time to use replacement filters is to check your water color. If it’s cloudy with a number of visible dirt or sediment particles, then you should check your cartridges and media layers. They may have become congested and ineffective, letting larger contaminant molecules through into your drinking supply.

"Hydrogen sulfide creates a rotten egg smell, while chlorine produces a bleach-like aroma. These are all signs that you should change or clean your cartridges." 

brita pitcher

The Bottom Line

Water filters are practical and simple tools that remove harmful contaminants from your household supply, purifying your tap water and saving your faucets from limescale deposits and sediment buildup. However, you must make sure that you’re replacing the media in these filters regularly. If you don’t, these cartridges will congest, break down, decay, and become ineffective at cleaning your water.

Jennifer Bellini

About the Author

Jennifer Bellini is a business guru who’s spent most of her life working in her home state of Wisconsin where she still lives with her family. Her experience lends itself best to sussing out the unique problems a business may face with their water quality. She is also our lead market analyst and is the driving force behind site growth.