When to Replace a Pool Cartridge Filter - Signs It Is Done

The 5 Signs It Is Time to Replace

1. Cleaning No Longer Restores Baseline Pressure

This is the most definitive sign. After a proper cleaning - hose rinse followed by an overnight soak in dedicated filter cleaner - the pressure after reinstallation should return to within a few PSI of your clean baseline.

If the pressure after a thorough chemical soak is still 5+ PSI above baseline, the cartridge media itself has degraded. The fibers have compressed and matted over years of use to the point where no amount of cleaning can restore them. The cartridge needs replacing.

2. Visible Tears or Holes in the Media

Hold the cartridge up to a bright light source - a strong flashlight or direct sunlight. Look through the pleated fabric panels.

New filter media is opaque - no light passes through. Degraded or torn media shows as bright spots where light comes through. Even a small pinhole allows debris to bypass the filter entirely. Any visible damage means replace immediately.

3. Cracked or Separated End Caps

The end caps are the circular plastic discs at the top and bottom of the cartridge that hold the pleated media in place and seal against the filter housing.

Check for:

• Cracks across the face of the end cap
• Separation between the end cap and the filter media (a gap where they meet)
• Warping or deformation of the plastic

A cracked end cap allows water to flow around rather than through the filter media, making the cartridge useless for filtration even if the media itself looks intact.

4. Permanently Collapsed Pleats

During normal operation, cartridge pleats compress under pressure. During cleaning, they should spring back open when you spray water through them.

Permanently collapsed pleats that do not open during rinsing indicate the internal spacer structure has failed. The effective surface area of the cartridge is dramatically reduced, causing rapid pressure rise and poor filtration. These cartridges cannot be restored by cleaning.

5. Age (2-3 Years of Regular Use)

Even a cartridge that passes visual inspection starts to decline in filtration efficiency after 2-3 years. The microscopic fiber structure of the media gradually changes in ways you cannot see.

If your cartridge is approaching 3 years old and you notice:

• More frequent cleaning needed
• Slightly cloudier water than when the cartridge was new
• Pressure rising faster than it used to

…it is worth replacing even if you cannot see obvious damage.

How to Choose a Replacement

Match the replacement cartridge to your filter housing model. The model number is printed on a label on the filter housing.

Use the model number to find the correct replacement:

• Pleatco - the most widely available aftermarket brand, good quality
• Filbur - another reliable aftermarket option
• Unicel - premium aftermarket, excellent longevity
• OEM brand (Hayward, Pentair, Jandy) - the original equipment manufacturer cartridge, most expensive but guaranteed fit

Replacement pool cartridge filters on Amazon - search by your filter model number for exact-fit options.

Avoid: Very cheap no-name cartridges from unknown sellers. They typically last under a year and often have thinner media that does not filter as effectively as name-brand equivalents.

What About Cleaning vs Replacing?

Chemical cleaning adds months of life to a cartridge and should be done before deciding to replace. But once a cartridge has degraded past the point where cleaning helps, continuing to clean it wastes time - replace it.

Related Guides

• How to Clean a Pool Cartridge Filter - proper cleaning technique
• How Often to Clean Pool Cartridge Filter - cleaning schedule
• Best Pool Cartridge Filter Cleaner - tested cleaners
• Cartridge Filters Complete Guide - all cartridge filter topics