How Do I Know When I Need a New Pool Filter? Cartridge Filters

“How often do I replace my pool filter?”

“Do I replace my pool filter every year?”

We get asked any variation of this question about once or twice a week. Unfortunately, there’s no easy answer when it comes to “How Often.” We’re going to list a few of the signs you should look for that are dead giveaways that it’s time to replace your filter. And in this list, we’re only discussing catridge filters – we’ll discuss DE filters in a later post.

First, let’s start with the basics. If you’re not familiar with the type of filter you have, you can usually tell by looking at the filter housing. A cartridge filter is usually (not always) a cylinder shape, and normally black or tan. If it looks bigger around than it is tall, you probably have a DE filter, and again, we’ll discuss those a little later.

The housing for a cartridge filter. This is a Hayward brand filter, but other brands look similar.

Once you’ve determined the type of filter you have, you can start inspecting it for any of the items below. You’ll need to remove the filter element out of the filter house, so here’s a video (not ours) showing how to clean a cartridge filter – just pay attention to the opening and closing steps.

Now that you have your filter element out, here are a few things to check to see if it’s time to replace your filter.

1) Broken Bands – Almost all cartridge filters have white or blue bands around them. They are about 1/4″ thin. If all of the bands are broken, it’s time for a new filter element. If only one band is broken, you’re probably ok, for a little bit longer.

2) Dirty or Slimy – If you clean the filter, and it still looks really stained, or has a slimy feel to it, it’s time for a new filter. If too much oil or dirt clogs the mesh of the filter, it makes it difficult for the water to flow through, and there are times cleaning products just won’t do the job for you.

oily slimy cartridge pool filter

3) Crack in Plastic on Top of Filter – This is actually a very common problem, and even if the filter is spotless, it needs to be replaced. I crack in the plastic ring is usually caused from a sharp edge in the house pressing down on it while putting the lid on. Once the plastic is cracked, water can pass through it much easier than passing through the actual filter area, making a large portion of the water circulating through your pool unfiltered.

These three signs are the most common to look for when determining if your swimming pool needs a new filter. Your filter is one of the most important parts of your pool, and should not be overlooked. As always, if you have any questions, ask us in the comments, or feel free to call or email us.

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  • Jeny Thomas

    Thanks for sharing this informative post and video. No doubt when quality filter cartridges are used you need to worry less about the maintenance of the swimming pool.

  • Ronny Anderson

    This is a great article, often we missed to consider when we need a new filter, but after reading your post it has been clear.
    Thanks for sharing.

  • Semi Ali

    Thanks for sharing. I have a question about our 36000 gallon UV system pool, renovated about two years ago. We have been successfully maintaining it until we were having to clean the cartridge filters nearly every week sometimes more. Eventually our pool turned green despite consistent cleaning. We ended up calling a local pool company to help us clean it up. After a week or so, they said we need a bigger pump- and that is why we are having trouble keeping the pool blue (charging 1700$ to do it) My question is- how did our pool last since 2002 with a small pump? Does this make sense? They did not say that the pump is old, they just said it isn’t filtering all the water. We have not replaced the filter cartridge in over a year or so. What do you guys think?