How to match a pool filter cartridge
Match a pool filter cartridge to the filter model on the tank and to the cartridge length from end cap to end cap. A cartridge that is too short lets water bypass the pleats, so the pool never gets filtered.
· 5 min read
Start at the filter tank
The model is on the filter label. Write down the brand and model, then the number printed on the end cap of the old cartridge if it is still readable. That number is the search term.
Measure the cartridge from end cap to end cap. Diameter is easy to get wrong on a pleated cylinder, so treat the model and the length as the pair that has to agree. Square feet of area, when it is printed on the cartridge, is the third check.
What a short cartridge does
A short cartridge in a tall tank leaves a gap. Water takes that gap and skips the pleats. The pressure can look fine while the water stays cloudy. People then blame the chemistry.
Replace the cartridge when the pleats stay gray and stiff after a real rinse, when an end cap is cracked, or when pressure climbs again within a few days of cleaning. How to rinse it, and how that differs from sand and DE, is in how to clean a pool filter.
If the water is cloudy anyway
A correct cartridge still needs the pump to move water and the chemistry to be in range. Haze with a clean filter is covered in why pool water turns cloudy. The general rule for any part number is in how to match a replacement part.
Cartridges and the tanks they fit are in equipment.
Questions
How do I find the right pool filter cartridge?
Use the filter brand and model on the tank label, the cartridge length from end cap to end cap, and any part number on the old end cap. A diameter you estimated is the weak check.
What happens if the pool cartridge is too short?
Water goes around it. Filter pressure can look normal while the pool stays cloudy. Match the length to the filter model.
How often should I replace a cartridge instead of rinsing it?
Rinse when pressure is about 8–10 psi over the clean baseline. Replace the cartridge when a thorough rinse no longer drops the pressure, when the pleats stay stiff and gray, or when an end cap is cracked.