How to Clean a Pool Filter: A Step-by-Step Guide

A clean pool filter ensures your pool water remains crystal-clear and healthy. The filter removes dirt, debris, and contaminants from the water as it circulates through the pool system. In time, it needs cleaning as it becomes clogged with trapped particles removed from the water, reducing its efficiency and straining the pool pump. 

While there are three main types of pool filters—sand, diatomaceous earth (D.E.), and cartridge—this article will focus on cleaning cartridge filters. Sand and D.E. filters are typically cleaned by backwashing to flush out accumulated dirt. To learn more about backwashing, read How to Backwash a Hayward Pool Filter.

Why Clean Your Pool Filter Cartridge?

Keeping your pool's filter cartridge clean is important for several reasons:

• Clearer water: A dirty filter is less effective at trapping particles, leading to cloudy or hazy pool water. 
• Healthier water: A clogged filter is the ideal breeding ground for bacteria and algae. They thrive on the organic matter that accumulates in the filter pleats. Regular cleaning helps prevent algae blooms and maintains proper water chemistry.
• Longer equipment life: As a filter becomes clogged, the pool pump has to work harder to push water through the dense media. The increased resistance puts additional strain on the pump motor, potentially leading to overheating and premature failure. 
• Proper winterization: If you live in a climate where you need to close your pool for the winter, you should thoroughly clean the filter first. Dirt or debris will be harder to remove come spring. A clean filter also prevents the growth of mold and bacteria while the pool is covered.

When to Clean Your Pool Filter Cartridge

Knowing when your filter needs cleaning is just as important as knowing how to clean it. Here are some guidelines for determining when it's time to clean your cartridge.

• Regular maintenance: For pools that are in use, aim for a monthly cleaning schedule. If your pool gets heavy use, such as frequent parties or a large number of swimmers, you may need to clean it more often.
• Pressure rise: Most pool filters have a pressure gauge that indicates when the filter media is becoming clogged. When the pressure reads 8-10 psi higher than the normal operating level (which you should note when the filter is clean), it's time for a cleaning.
• Winterized pools: Even if your pool is closed for the winter and not in use, the filter should still be cleaned every 3 months to prevent dirt from hardening and becoming difficult to remove.
• After special circumstances: Certain events can clog filters more quickly than usual, including heavy algae blooms, large pool parties, and storms or rainfall that introduce extra debris into the pool water. 

Steps to Clean a Pool Filter Cartridge

Now that you know why and when to clean your pool filter, let's walk through the steps of actually cleaning the cartridge.

1. Turn off the pool pump and relieve pressure

Before opening the filter housing, turn off the pool pump and relieve the pressure in the system. Locate the air relief valve on top of the filter housing and open it slowly to allow air to enter and equalize the pressure. You may also need to remove the drain plug at the bottom of the housing to allow water to drain out.

2. Open the filter housing and take out the cartridge

Once the pressure is relieved, you can safely open the filter housing. Most housings unscrew or unlatch, but consult your owner's manual for specific instructions. Carefully lift out the cartridge, noting its orientation so you can replace it correctly. If your system uses multiple cartridges, it's a good idea to number them so you can put them back in the same order.

3. Rinse cartridges with garden hose

With a garden hose spray nozzle, rinse the cartridges from top to bottom to remove loose dirt from the pleats. Start at the top and work your way down so the dirt flows downward and doesn't get trapped. For stubborn dirt, use a stronger spray setting or a nozzle attachment. You can also use a low to medium setting on an air compressor to blow dirt out of the pleats.

4. Inspect cartridges for damage

While the cartridges are out of the housing, check for signs of wear or damage. Look for cracks, tears, or areas where the media appears thin or worn. If you notice significant damage, it's best to replace the cartridge rather than attempting to clean it.

5. Soak cartridges in cleaning solution (if winterizing)

If you're cleaning your filter as part of your pool winterization process, it's a good idea to give the cartridges a deep clean by soaking them in a cleaning solution. Soaking the cartridges overnight in a 1:1 mixture of water and vinegar is an effective and natural deep-cleaning process. 

Alternatively, for a stronger clean, you can soak them in a 1:20 solution of muriatic acid and water for about an hour. You can also buy cartridge cleaning products and use them according to the manufacturer's instructions.

6. Rinse cartridges thoroughly and allow to dry

After soaking, rinse the cartridges thoroughly with a hose to remove any remaining dirt and cleaning solution. Make sure the cartridges are dry before putting them back in the filter housing. This is also a good time to clean the inside of the empty filter housing.

7. Reinstall cartridges in filter housing

Once the cartridges are clean and dry, place them back into the filter housing in the same orientation they were in originally. If you numbered multiple cartridges, make sure to put them back in the correct order. To prevent leaks, lubricate the housing o-ring with a silicone-based lubricant before closing up the housing.

8. Close and secure filter housing

Following the manufacturer's instructions, close up the filter housing and make sure it is properly secured. Double-check that the air relief valve and drain plug are also closed.

9. Turn the pool pump back on and check for leaks

With everything back in place, turn your pool pump on and watch the filter housing closely for any signs of leaks. Also note the pressure gauge reading, which should be back to the normal operating level now that the filter is clean.

How Often Should Pool Filters Be Cleaned?

The frequency of cleaning your pool filter depends on a few factors, such as the size of your pool, how often it's used, and environmental conditions like nearby trees or windblown dust.

• Single cartridges: For most residential pools with a single filter cartridge, aim to clean the filter every 30 days. This ensures that the filter media doesn't become overly clogged and that your pump isn't straining to push water through.
• Quad-cartridge setups: If your pool uses a larger, quad-cartridge filter setup, you may be able to extend the cleaning interval to every 4 months. However, keep an eye on the pressure gauge and be prepared to clean sooner if the pressure rises significantly.

When Should I Replace My Pool's Filter?

Even with regular cleaning, filter cartridges don't last forever. Most cartridges last about three years before they need to be replaced. However, several factors can shorten this lifespan and necessitate earlier replacement.

• Frequent cleanings: If you find yourself having to clean your filter more and more frequently to maintain normal operating pressure, it may be time for a new cartridge.
• Visible wear: If you notice fraying, tearing, or thinning of the filter media, the cartridge's structural integrity is compromised, and it should be replaced.
• Persistent high pressure: If the filter pressure remains high even after a thorough cleaning, the media may be too worn to function properly.
• Age: Regardless of visible condition, if your cartridges are more than 3 years old, it's a good idea to replace them as a preventative measure.

Atomic Filters stocks a comprehensive range of replacement pool filters compatible with Filbur, Pleatco, Unicel, and many other leading pool filter brands. Our filters offer unbeatable quality at a huge discount.

Pool Filter Cleaning FAQ

Can you use vinegar to clean a pool filter?

Yes, soaking your filter cartridges in a 1:1 solution of water and vinegar overnight can help remove built-up dirt and grime. Vinegar is a mild acid that dissolves mineral deposits and organic matter. After soaking, be sure to rinse the cartridges thoroughly before putting them back in the filter housing.

Can you use bleach on pool filters?

No, you should not use bleach to clean your pool filter cartridges. Bleach is a strong oxidizer that can break down the fibers in the filter media, causing premature wear. Stick to milder solutions like vinegar or commercial cartridge cleaners.

Can you put pool filters in the washing machine?

No, putting your pool filter cartridges in the washing machine is not recommended. A washing machine will damage the delicate filter media, and detergents can leave residues that are harmful to your pool water chemistry. Always clean your cartridges by hand according to the manufacturer's instructions.

What chemicals should I avoid when cleaning my pool filter?

Avoid using any strong oxidizers or harsh detergents on your pool filter cartridges. This includes bleach, laundry detergent, and automatic dishwasher detergent. These products can degrade the filter media and leave harmful residues in your pool water. Stick to mild acids like vinegar or products specifically designed for cleaning pool filters.