How to Clean a Pool Cartridge Filter

If you’ve got a cartridge filter in your pool, you’re not alone! Pool filter cartridges are becoming a popular alternative to sand and glass pool filters. This is because they’re relatively inexpensive, easy to install and extremely effective at keeping your pool clean. 

But that’s not all. Cartridge pool filters are one of the most climate-friendly filters available. Since they don’t need to be backwashed, you can save hundreds of litres of water, and because they can operate at lower flow rates, you can lower your energy bills too. 

Sounds like a no-brainer, right?

But to get the most out of your pool filter cartridge, it needs to be looked after – and that’s where cleaning comes in. This can seem daunting to new, busy or inexperienced pool owners, but it’s not as difficult as it seems. If you can turn on a pool pump and operate a pool cleaner, you can clean a pool filter!

In this guide, we’ll give you an overview of what your pool filter does, how to clean it correctly and what you can do to keep it in peak condition all year round. Let’s jump in!

What is a pool filter cartridge?

A pool filter cartridge is a cylindrical filter that contains a pleated element – usually made from paper, cotton or polyester – that filters particles or impurities from your pool. It works together with your pool pump to keep your water filtered and clear. The pump forces water into the filter tank, where it flows through the paper or polyester pleats. These capture any debris before the water is syphoned back into the pool water.

Unlike sand filters, which use depth filtering (i.e. particles get trapped in a path), cartridge pool filters use surface filtering (i.e. particles remain on the surface). This means that instead of backwashing to remove debris, the pleated filter is removed from the tank and hosed down. 

In general, pool filter cartridges can trap particles between 10–20 microns (compared to 20–40 microns for sand) and perform well at slow speeds. They’re also low maintenance and use less water to clean, making them a popular choice for most backyard pools.  

Why do you need to clean a pool filter cartridge?

Your pool filter is a lot like a kidney. As water circulates, the filter’s tight mesh captures bacteria and debris and keeps it out of the pool water. Over time, however, debris can build up and clog your filter, making it difficult to keep your pool water clean. This can result in damage to your filter pleats and/or recontamination of pool water. 

When should you clean your pool filter cartridge?

There are a few ways to find out if your filter needs cleaning. The first is to check the filter gauge. Do this as part of your weekly pool maintenance. If the reading is 8–10 PSI (pounds per square inch) above the normal filter level, it’s time for a clean. If you’re unsure of what’s normal for your filter, check your manual or speak to a pool professional. 

Second, check your pool diary (you keep one, right?). If it’s more than three months since you cleaned your filter, it’s time to fire up the hose and give it a deep clean. However, if it’s less than 3 months and your pool water is cloudy – despite running your pump regularly, sanitising and cleaning your pool – then you could have unexpected build-up in your filter. This is common after frequent use, heavy rain or leaf falls. Generally, we recommend you give your cartridge filter a quick hose down every 2-3 weeks. 

How to clean your pool filter cartridge 

It’s a good idea to put aside half an hour or so to clean your pool filter. If it’s particularly dirty, it may require longer (e.g. overnight). Below is our step-by-step guide:

Step 1. Gather your tools

Before you do anything, get all of your tools ready. There’s nothing worse than scrambling around looking for a hose attachment or making last-minute trips to the pool shop. Here’s what you need:

• Garden hose
• Large bucket
• Gloves
• Protective eyewear
• Screwdrivers (if your cartridge lid has screws)
• Pool filter cartridge cleaning tool 
• Pool filter cleaner
• O-ring (if needed)
• Lubricant (if needed)
• Replacement pool filter cartridge (if needed)
• Owner manual

Step 2. Turn off the pool pump

The first thing to do is turn off your pool pump. This will stop water from entering the filter or shooting up in the air. Next, turn the air valve to the open position to relieve pressure. Give it time to release before moving to the next step. 

Step 3. Open the filter tank lid

If your filter tank has an O-ring clamp, open it using your filter manual’s directions. You may need to press a release tab or turn the locking knob. If your filter lid is held down by clamps and screws, remove the screws and put them in a small container so they don’t roll away!

Step 4. Remove the filter

Pull out the filter carefully. If you have more than one filter in the housing, remove them all. Don’t be surprised to find the filter clogged with hair, algae and leaves. It may even be greasy as a result of body oils and sunscreen!

Step 5. Rinse the filter

Using a garden hose, start rinsing the filter. Spray at an angle from the top and work your way down. This will ensure that debris is pushed down (and not further into the pleats). Make sure you don’t use a high-pressure cleaner as it could damage the material. 

If you need to clean the pleats, consider using a cartridge cleaning tool. This attaches to the hose and helps you access narrow gaps. But don’t be tempted to use a soft brush. This can cause rips and make your filter ineffective. 

Pro tip: To save water, hose the filter over soil or grass instead of a drain. This allows it to feed your plants or lawn instead of being wasted. Also, pool water debris is usually organic, so it’s perfectly safe to put it in your soil. Check out this quick demonstration from @theaussiepoolguy:

Step 6. Check for damage 

Now that the debris has been removed check the condition of the housing and pleats. If you see cracks or tears, it’s time to replace your pool filter cartridge. Note: If your filter pleats are no longer white, don’t worry. This is perfectly normal and won’t affect your filter’s ability to do its job. 

Step 7. Give it a deep clean

If you’ve still got residual stains, grease or calcium build-up after hosing, your filter needs a deep clean. This means bringing out the big guns – pool filter cleaners. These products are designed to strip sunscreen and other residue from filter elements that help extend filter life. When you handle them, make sure you use gloves and protective eyewear. 

Follow these steps for a deep clean: Pour a pool filter cleaner into a large bucket following the instructions on the bottle. Add the cartridge into the solution, making sure it’s completely covered. Turn it over if you need to. If the stains are stubborn, you may need to soak the cartridge overnight. 

Pro Tip: Remember to follow the manufacturer’s instructions when disposing of any chemical cleaners. Some can pollute waterways and be toxic to humans, animals and plants. 

Step 8. Let it dry

Put your filter outside to dry completely. When this is done, give it a shake to remove any dry debris. Drying is also a good strategy when you’re doing a quick rinse every few weeks. Residue can be easily shaken off this way. But don’t leave the cartridge in the sun for more than a few hours. While UV light can kill algae spores, it can also deteriorate the housing and material. 

Step 9. Return the filter to the tank

Now that it’s clean and dry put the filter cartridge back into the tank. Clamp the top shut if necessary. If you have an O-ring, make sure it’s in good condition and add lubricant to prevent sticking or abrasion. If the ring is cracked or broken, replace it with a new one. Make sure your pressure relief valve is open when closing the filter lid.

Step 10. Turn on the pump

Turn on your pump and close the air release valve once water starts flowing from the valve. Make sure everything is operating normally and that the PSI reading is within normal range again. If everything’s sweet, you’re ready to start swimming again!

Can I backwash a pool filter cartridge?

Cartridge filters aren’t designed to be backwashed, so don’t even try! Unlike sand filters, there’s no reverse water flow function (or backwash line), so you’ll have to clean them manually. While this might seem time-consuming, it can save you water and energy consumption in the long run, making them more eco-friendly than media filters. 

How often should I replace my pool filter cartridge?

This depends on a few things, like how big your pool is and how frequently you clean it. In general, you should change your pool filter cartridge every three to five years. If you’ve got a variable speed pump, which can filter water more slowly, it may be longer. This puts less pressure on your pool filter cartridge and increases its longevity. 

However, if you ever notice broken bands, cracked endcaps or tears in the accordion-like pleats during regular maintenance, replace the cartridge immediately. Also, if you’ve cleaned your cartridge and your water still isn’t filtering properly, there may be damage you can’t see, in which case it should be replaced.

How do I maintain my pool filter?

You don’t have to wait for your PSI to be high to clean your filter. Give it a hose every three to four weeks to prevent build-up. You can do this more often if you get a lot of leaf litter or heavy rain. A deep clean should be scheduled every three months to remove stubborn particles. This can prevent filter damage and poor water quality. 

Another thing you should do is keep your pool water balanced. This can prevent algal growth and scaling, which can block or damage your filter. Also, empty your skimmers regularly so the debris doesn’t wind up in your filter. Last, make sure you run your pool cleaner regularly. This will pick up excess debris and prevent your pool filter from getting overworked.

Final thoughts

While cleaning your pool filter cartridge can seem like yet another pool maintenance task, it’s one of the most important. Why? Because it keeps your pool water cleaner for longer. Together with your pool pump, it’s critical for the health of your pool. In fact, a well-maintained filtration system means fewer pool chemicals, less pool cleaning and – best of all – more swimming! 

To find out more about Zodiac pool filter cartridges, contact one of our authorised dealers. For more pool care tips and tricks, dive back into our Pool and Spa Guides.