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How Often Should You Change an Under Sink Water Filter

By: Craig Smith
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How Often Should You Change Under Sink Water Filter

Using an under-sink water filter is a great alternative to buying bottled water.  You’ll save big money and get great tasting water without lugging tons of bottles home!  

But how often should you change your under-sink water filter?

You already know that under-sink water filters can make disgusting water into something more drinkable. But that’s only the case if you put fresh filter cartridges in at the right time.

In this post, we discuss how often you should change out your filter cartridges, and we discuss some of the factors that can play a part in filter life.

How Long Do Under-Sink Water Filters Last?

The length of time cartridges for under-sink water filters last depends on a variety of factors. On average, you can expect around six months. Different manufacturers recommend different timeframes, and some multi-filter systems have different cartridge replacement schedules for each one.

Some of the factors that can change your filter life are:

  • Water quality
  • Filter type
  • Filter quality
  • Water usage

We take a more detailed look at each of these factors below.

Water Quality

The quality of your water supply makes a big difference in how often you’ll need to change out your under-sink water filter cartridges. This is because some water supplies, even city water, are of poor quality with a high amount of sediment, and will therefore clog your filter faster.

This applies to any kind of contamination, including lead, bacteria, or chlorine. If your under-sink water filter removes a contaminant, that contaminant clogs the filter over time.

Filter Type

Some under-sink water filter systems have multiple filters. Each of those may have different schedules for when to change them. This is especially true in reverse-osmosis filtration systems. 

A lot of standard filter cartridges last 6-9 months, depending on the manufacturer. A pre-filter requires replacement every 6-9 months. You should replace an RO membrane about every two years. For a post-filter, you can expect about one year between changes. 

These are just the average lifespans, and it could be different for your filter. Also consider the filter quality. A lower-quality filter does not filter as well or last as long as a high-grade filter does. 

Water Usage

How much water you use is one of the biggest factors in how quickly the cartridges in under-sink water filters wear out. This is because the actual filtration capacity of a water filter is not measured by length of time, but by number of gallons. Factors like the water quality can make a filter fail earlier than this estimate, but this is the amount of water the filter is designed to clean.

This means some under-sink water filters reach the end of their service life quicker than others. If you drink 100 gallons of water each month, a filter will only last half as many months as if you drank only 50 gallons per month.

Some people also use filtered water for cooking, not just for drinking water. If you do that, you’ll reach your capacity much quicker. 

Tell-Tale Signs a Filter Changing the Filter Is Necessary

There are some signs you’re under-sink water filter needs a filter change. 

Poor Taste or Smell

If your water doesn’t taste right or your water has picked up a strong odor, there’s a good chance your filter has expired. It isn’t doing its job correctly, and it may not remove contaminants, the unpleasant taste, or the bad odor the same way it did before.

Cloudy Water

As a water filter starts to fail, you may begin to notice your water becoming cloudy. You may see sediment floating in it, or it may just look slightly more translucent than usual. This means the filter isn’t doing its job, and it is time to replace it.

Low Water Pressure

Water flow and pressure through under-sink filters may decrease when it becomes dirty. If you start to notice it taking exceedingly long to fill your glass, you probably need to change out your filters. 

While you can expect a small decrease in pressure through the service life of the filter, any sudden change could mean you have a clogged cartridge. Even a gradual decrease in pressure eventually becomes enough to signal it’s time for a replacement.

Why It Is Important to Change the Filter


It is important to change out your under-sink water filters at the proper time. A clogged filter, or a filter past its useful lifespan, can cause a variety of problems. Changing them when they need it can even end up saving you money in the long run.

But replacements cost money, and you want to use them as long as possible. Still, it’s better to err on the side of changing a water filter too soon rather than too late. Remember, even with this additional cost, it’s still cheaper than drinking bottled water.

Here are some of the reasons to change your filter at the correct time:

  • Doesn’t filter – A clogged cartridge may not do anything, and could pass all the sediment and harmful contaminants right through to your drinking water.
  • Water pressure loss – If your filter is clogged, it could result in very low water pressure from the faucet. It could also decrease the water flow to such a rate that you just can’t use it at all.
  • Leaks – A clogged filter could cause the water to leak out of the housing. This can damage cabinets and under-sink water filtration systems.
  • Unhealthy – If your filter is no longer working properly, it could allow through heavy metals, chemicals, and VOCs.

Replacement Filter Cost

The type of water filtration system can make a big difference in how much replacement filters cost. In general you can expect to pay $40-160, or about $70 on average. 

Always make sure to buy replacements that are NSF certified. If you buy generic filters that aren’t certified you could end up with knock-offs that don’t work as well or last as long. In the end, that could end up costing you more because you’ll need to replace them sooner.

Sometimes you can buy filters in multiple packs. While that is a bigger layout upfront, it can save a lot of money over the long run. You can also buy complete sets for some under-sink filters that use multiple cartridges, which could be cheaper than buying each filter individually.

Other Tips For Changing An Under-Sink Filter

Here are some other tips to keep in mind:

  • Add filter changes to your calendar or set a reminder on your phone ahead of time so you don’t forget.
  • Check to see if your filter manufacturer sends out replacement reminders. Some do this, others don’t, but they can be a great way to make sure you remember.
  • Check into a subscription service for your cartridges. By doing this, you’ll have a fresh set arrive on your doorstep at the right time, making it difficult to miss a scheduled replacement.
  • Always inspect the cartridge you remove to make sure you need to change them. If it looks clean, you could delay the change until it is necessary. Over time, this can save money.
  • Always run water through your filter for five minutes before drinking it. This allows contaminants and impure water to flush from the faucet and lets any loose sediment flush from the new filter.
  • Keep a tray or trashcan handy when changing the cartridges. It can be messy, and you don’t want the old filter dripping all over.

In Conclusion

In this post, we’ve discussed how often you should change out the cartridges in your under-sink water filter system. We also talked about the signs that can show when a filter change is necessary, and we talked about the importance of completing the job in a timely manner. 

We also discussed the cost of filter cartridge replacements and we gave some tips to keep in mind when changing your filters. If you follow all of these tips and change your filters on schedule, you’ll continue to enjoy pure filtered water. 

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Craig Smith
Craig got his start in water working in the swimming pool and spa industry. Water treatment would grow into his main career but he ended up working in the pool industry for over 26 years where much of his time was spent balancing the water in customer's swimming pools and installing water filtration equipment. Craig offers an abundance of water treatment knowledge after helping homeowners get pure water for 26 years.

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