Cartridge filters cannot and should not be backwashed - they use a completely different cleaning method. Instead, you remove and rinse the cartridges or replace them when cleaning no longer restores proper flow.
Cartridge filters cannot be backwashed. If your system has cartridge filters, there's no backwash valve or setting because the cleaning process is entirely different from sand or DE filters. Attempting to backwash a cartridge system won't accomplish anything and indicates a misunderstanding of how your filtration works.
Understanding the difference helps explain the cleaning approach. Sand filters trap debris in the sand bed and reverse water flow during backwashing to flush out contaminants. Cartridge filters use pleated fabric material that physically captures particles as water passes through - there's no media bed to flush clean.
The cartridge material becomes saturated with oils, lotions, and fine debris over time. This buildup can't be removed by reversing water flow because it's embedded in the filter fabric itself.
If your filter pressure has increased significantly above the clean starting pressure (typically 8-10 psi, but verify with your manufacturer), it's time to clean. Here's the systematic approach:
If rinsing doesn't restore proper flow or the cartridges look dingy, you'll need a deeper cleaning approach. Soak the cartridges in a filter cleaning solution designed for cartridge filters. Many pool owners rotate between two sets - one in use while the other soaks and dries.
For heavily soiled cartridges with oil buildup, dishwasher detergent (not soap) can help break down body oils and sunscreen residue. Mix according to package directions and soak for several hours. Verify this approach is suitable for your specific cartridge material and consult manufacturer guidelines.
If you're unsure whether you have cartridge filters, here are the telltale signs:
Sand filters have multiport valves with settings like "Filter," "Backwash," "Rinse," and "Waste." DE filters may have backwash capability but use diatomaceous earth powder. Our complete filter types guide can help you identify your system definitively.
Cartridge filters don't last forever, and knowing when to replace versus clean saves time and maintains water quality:
Clean the cartridge if: Rinsing restores normal pressure and the pleated material looks relatively white or off-white. The fabric should spring back when pressed.
Replace the cartridge if: The material has become gray or brown despite cleaning, the pleats have flattened or frayed, or cleaning no longer reduces pressure effectively. Cartridges generally need replacement every few months, commonly in the 2-4 month range, but this varies significantly based on bather load, environmental factors, and manufacturer specifications.
Unlike sand filters that you backwash weekly or bi-weekly, cartridge maintenance follows pressure readings rather than a strict schedule. Check your pressure gauge regularly - when it reads significantly higher than the clean starting pressure (check your manufacturer's recommendations for the specific threshold), it's cleaning time.
I'd suggest keeping a log of cleaning dates and pressure readings. This helps you establish a pattern for your specific pool and usage. High-use periods like summer parties or after storms may require more frequent attention.
The key difference from backwashable filters is that cartridge systems require you to stop filtration completely during cleaning. Plan accordingly, especially during heavy use periods when continuous filtration is important for water clarity.
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