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Home » Water Filtration Systems » How to Change an Under Sink Water Filter Cartridge

How to Change an Under Sink Water Filter Cartridge

By: Craig Smith
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How to Change an Under Sink Water Filter Cartridge

If you have an under-sink water filter system, you may be cowering in fear over the thought of changing out the filters. 

We’re here to help. 

In this post, we give step-by-step instructions on how to change cartridges in a typical under-sink water filter.

It is understandable that some people don’t look forward to changing their filters. But you don’t want to continue using a filter past its useful lifetime. That can result in contaminated, smelly, and just disgusting drinking water.

Don’t do it. Change those filters so you’ll have nice, clean filtered water.

Follow the steps below, and you’ll have your new filters in place in no time.

How to Change an Under-sink Water Filter Cartridge

There is a huge range of under-sink filtration systems available. It may surprise you to find that you can change the filter on most of them with the exact same steps. While there are under-sink water filter systems that work differently, the steps below work on the majority of water filters, and probably yours as well.

1. Gather Your Tools And Supplies

The first thing to do is gather up your tools and supplies. Don’t stress too much over this, you probably have most of these already. Here’s what you’ll need:

  • Replacement filter cartridges
  • Towels
  • O-rings (sometimes included with new water filters)
  • A flashlight (optional)
  • Water filter wrench

If you don’t have the filter cartridges yet, you’ll need to get those. Double-check to see if they come with new o-rings, and get some of those if they don’t. You may need to look up what size fits your system. 

Water filter wrenches are available in solid metal or plastic designs. These are sometimes specific to your filter. A Whirlpool filter may require a wrench like the one below, while a different filter may need one specific to that brand.


There are strap-wrench designs available. The strap-style housing wrench style works well with almost any filter, no matter the size. You may already have one like it that you use for the oil filter on your car. If so, the same wrench will work on your water filters.

One such wrench is this EcoPure strap wrench:


2. Turn Off The Water Supply

Before changing the filter, you need to shut down the water going to it. 

You may have a bypass valve under your sink, right next to the water filter. If so, turn that valve to the bypass position to prevent water from flowing into your filter.

If you can’t find a bypass valve, there is usually a cold water valve under your sink that supplies cold water to the filter and faucets. You can shut that down instead.

If there isn’t a cold water shutoff under your sink, you may need to shut the water off to the whole house. Locate the point where water enters your home and you should find a shutoff valve near it.

3. Depressurize The Filtration System

Before you change out your filter, you need to release any pressure inside it. An easy way to do that is to turn the faucet connected to your filter and let it run for a minute. This will release the pressure on the filter and make it easier to open when changing.

4. Remove Filter Housing

Now is when you make use of that water filter wrench. Slide the wrench onto the filter housing. If it is a strap-style housing wrench then you may need to tighten it so it grips your filter.

If there is room, you may want to put a towel or small tub under the filter to catch any water that may drip or that you may spill.

At this point just rotate the filter housing in a counterclockwise direction to unscrew the filter. Stuck water filter housings may require quite a bit of pressure to loosen. 

Filter housings may contain a lot of water, so be careful to direct the filter housing into a plastic tub or keep it upright to avoid making too much of a mess.

If your system has multiple filters, change them out one filter at a time so you don’t mix them up.

5. Remove Filter Cartridge From Housing And Inspect Things

Slide the filter cartridge out from the housing at this point. Inspect the cartridge so you can see if you need to perform a filter change earlier next time. If a cartridge has a lot of buildup then it’s a sign it has been too long since you changed it.

There is an o-ring at the top of the housing. If you don’t have new o-rings, inspect the existing o-ring carefully for damage. If you have a replacement o-ring, now is the time to remove the old one and swap in the new one.

6. Clean The Filter Housing

It’s a good time to clean things up, since you have it apart already. This area is wet all the time, so you can reduce the chances of mold or mildew taking hold if you give it a good cleaning now.

Warm soapy water works well for this. Mix a solution using dish liquid, then use a good brush to scrub all the surfaces, paying careful attention to the inside of the filter housing.

7. Sanitizing The Water Filter System (optional step)

If you see any evidence of mold buildup, any black deposits, or any signs of algae, you’ll want to sanitize your under-sink filter. 

Create a sanitizing solution by mixing a gallon of water with about three tablespoons of household bleach. Make sure to remove all the filter cartridges and then reinstall all the empty housings on your water filter system, adding a cup of your solution to each housing.

Turn your water supply back on and run water through the faucet connected to the filter. Run just long enough for water to begin flowing from the faucet, then turn it off. 

Let this solution sit in your filter for about 30 minutes. At that point, shut your water supply back off and remove your filter housings. Dump the sanitizing solution down the drain to dispose of it..

8. Install New Filter Cartridges

This part is easy, you should be able to just slide a new filter cartridge down into each housing. Make sure you seat the replacement filters properly before you reinstall the housings. 

9. Turn On The Water

You can now turn the water back on. Do this slowly to prevent any chance of damage from a water pressure surge.

10. Flush The Filters

Now you need to turn on the water faucet that connects to your filter. Let it run for at least five minutes to let everything flush out well. 

11. Check For Leaks

After flushing the water system, close the faucet and inspect for leaks. Especially check around the housings you removed and reattached. If you don’t find any leaks, you can now enjoy fresh filtered water. 

Take care of any leaks you find at this point. Check to make sure the filter housings you removed are snug. You may need to shut the water off to remove the housings again so you can double-check the o-rings.

In Conclusion

We’ve described the process of how to change cartridges in an under-sink water filter system. Now you can see, it’s not as hard as some people fear. Don’t spend a lot of money on a plumber, there is a good chance you can change your own under-sink water filters and save. 

Check out the Best Under Sink Water Filters here.

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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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