How Does My Refrigerator Know When to Change Filter?

How Does My Refrigerator Know When To Change Filter?

Many modern refrigerators make use of water filters to provide us with chilled, clean water. These filters have a finite capacity to treat water before they have to be replaced. Fortunately, a lot of new refrigerators can alert you when it’s time to replace the filter — but how does the refrigerator know that the filter needs to be changed?

Refrigerators use a timer to alert users that the filter needs to be replaced. The monitor keeps track of when the filter was installed and the service life of the filter to determine when it is due for service.  Most of these automated timers require you to reset the alert notification when replacing the filter in order to reset the timer.

With many refrigerator owners unsure whether they should act on the alert to replace the water filter, it’s understandably of interest. Read on to learn more about how your refrigerator knows when it is time the filter and what steps you should take.

Read my ultimate guide on refrigerator filters.

Do I Need to Change My Water Filter as Soon as the Alert Goes On?

Refrigerator manufacturers conduct rigorous testing to understand the effectiveness of their water filters. They used the results of this testing along with an understanding of how much water the typical person consumes to establish a filter life.

One of the most important elements of this is to understand how ongoing use of the water filter — under normal household conditions — will impact its effectiveness. Important factors related to filter performance include:

  1. ability to filter out particles
  2. reduction in water pressure
  3. adsorption capacity of the activated carbon
  4. potential for bacteria to grow in filter media

Let’s look at these in more detail to understand what happens to the filters over time.

Related article: 9 Signs It’s Time to Replace Your Refrigerator Filter

1. Large particles

As water flows, it naturally carries with it small particles, which are carried with it. The vast majority of particles are removed from the water when it is treated, usually using a process called sedimentation. This process lets particles come to rest under gravity at the bottom of the body of water so that they can be removed more easily.

Not all of these particles are able to be removed, though, and there can be tiny particles making their way into the water supply all the way up to your property too. This means that it’s entirely normal to expect a small number of tiny particles to be present in water piped into a house.

One of the jobs of water filters is to help filter out those particles. Particles of a significant size will be mechanically removed using a physical filter layer to prevent them from passing through.

One consideration when assessing water filters is their ability to remove these particles on an ongoing basis. If the layer responsible for the mechanical filtering degrades, you may, over time, begin to see more of the particles not being effectively filtered.

2. Water pressure

The continual trapping of small particles by a water filter can begin to reduce the amount of room available for the water to flow through the filter, impacting water pressure.

Another reason for this is that there are elements present in water that can react with different substances. One common example is the number of dissolved minerals in the water, which can, over time, lead to calcification. The most common minerals dissolved in the groundwater that makes their way to our tap water include:

  • Sodium
  • Calcium
  • Magnesium
  • Potassium
  • Chloride
  • Bicarbonate
  • Sulfate

Calcification is the synthesis of solid pieces of calcium carbonate from dissolved minerals, which can also provide a robust physical barrier to the amount of water able to pass through.

A decrease in water pressure will mean that it takes longer to fill your glass using the water dispenser in your refrigerator. One of the challenges with this slowdown is that it happens gradually, so it can be difficult to notice day-to-day.

3. Capacity of activated carbon

The most crucial component of a water filter in a refrigerator is activated carbon. This provides an extremely high surface area across which the water can flow, maximizing the ability of the carbon to react with different contaminants in the water.

Activated carbon has been shown to be effective at removing certain elements from water, including lead — which can be extremely hazardous to health. The activated carbon is also highly reactive with chlorine and so can have a significant impact on the taste of the water, given that chlorine is one of the top reasons given for an unpleasant taste from tap water.

4. Bacterial growth in filter

While water filters don’t often operate at the right size of filtration to actively remove bacteria such s E. coli from the water, bacteria can still collect in water filters over time. This is because water filters provide a damp surface on which they can grow.

The bacterial build-up is an important consideration because it’s not the same as wear and tear. It’s more reflective of the impact of having a consistent filter for which water to flow over time.

So, Should I Change My Filter Right Away?

It’s impossible for water filter manufacturers to know exactly what the usage for a particular water filter is, so they take a view as to what an ‘average’ level of usage might be for a household.

With this in mind, the answer is that it depends. Think about your household usage and how this stacks up versus the ‘average’ household, which is likely a family of 3–4.

When looking at this comparison, you might find that your usage is probably a lot higher than the average, and in this case, you probably should act relatively quickly. If you believe your usage is lower than average, though, you might consider waiting longer.

If choosing to ignore the alert and wait a little longer, you should be on the lookout for the warning signs of the water filter starting to struggle. Measuring the time it takes to fill a glass of water and visually inspecting for sediment in the water are two examples of that. Most importantly, though, be especially aware of the risk of bacterial build-up over time to avoid exposing your household to infection.


It’s not the most straightforward decision on whether you should change your filter straight away based on the timer in your refrigerator. While the safest option is likely to change the filter without delay, there are a few factors to take into account and so it’s worth ensuring you understand them ahead of holding off for too long.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

Recent Posts