Cleaning your filter cartridge is fairly simple, and you don’t need any special tools or cleaning solutions for removing debris — in fact, the only thing you need is access to a hose. It should only take about a half hour to complete this 10-step process:

1. Turn off the power to your pool pump. This is always important when working with electricity, but it’s especially critical if your filtration system runs on an automatic timer.
2. Open the valves on the filter. The air relief valve releases the pressure, and the ball valve drain the water from the filter.
3. Remove the lid from the tank. Yours might have a lock ring, clamp, or knob, depending on your model.
4. Remove the cartridge from the filter canister. A gentle rocking motion while lifting up might help to dislodge the filter elements.
5. Set it down in a good spot for cleaning. Remember, you’ll end up with debris like decomposed leaves, silt, and fibers, so choose someplace that makes it easy to scoop up afterwards.
6. Inspect the cartridge for damage. Before cleaning, look for cracks, tears, or other damage. Even a small tear will decrease your filter’s performance.
7. Hose off the cartridge.
   • Use moderate pressure from a regular garden hose (no pressure washers!!).
   • Hold the hose at a 45-degree angle to avoid damaging the filter.
   • Spray off the cartridge from the top down until the debris is gone.
   • Flip over the cartridge and repeat the spray from the other direction.
   • Flush out debris out from between the pleats. You can also carefully brush the pleated surface to remove small particles.
8. Reassemble the filter canister. Slide the cartridge back into the canister, then replace the filter lid and tighten it down to seal the system.
9. Turn on the power to the pump, and restart it. If it seems sluggish to restart, it may need to be primed.
10. Close the air relief valve. Wait until a steady stream of water starts to spray out, then you can shut it.

Pro tip: At least once a year, soak your cartridges overnight (or about 10 hours) in a cleaning solution to remove excess build-up. You can find cleaning solutions at your local pool store.

What NOT to Do When Cleaning Your Cartridges

• Don’t keep filter cartridges forever. If you’re seeing inadequate filtration (i.e., your filter system is running but you still find excessive debris and cloudy or dirty pool water) but you aren’t noticing a rise in pressure, this likely means that your filter cartridges are torn or worn out and must be replaced. Remember that the cartridges are reusable, but at some point, they will lose their efficacy and simply allow water to pass through without filtering it.
• Don’t use a power washer on cartridges. The force of a power washer can destroy the filter cartridges by breaking down the mesh material, which is usually made of paper or a thin fabric.
• Don’t worry if the filter mesh isn’t perfectly white. If you’ve followed the cleaning steps but your cartridge film still doesn’t look brand new, that’s OK. As long as you don’t see debris or excessive build-up that can block the filter system from doing its job of keeping your pool water clean, some discoloration is fine – and even expected over time. If you are unsatisfied with the cleanliness of your filter, you should consider buying a bottle of filter cleaner from your local supply store.

How can you tell when it’s time to clean your filter cartridges?

Dirt and debris collected on the filter will restrict water flow through the system. You might notice decreased water flow and weaker suction of your pool cleaner. When this happens, pressure within the tank rises. When the pressure hits the level specified by the manufacturer (usually somewhere in the neighborhood of 8-12 PSI above the recommended starting pressure of your pool filter), it’s time for a cleaning.

Of course, it all depends on your volume of swimmers, but plan to clean your cartridge filter every two to six weeks. If your cartridge filter isn’t clean, it won’t work efficiently. You’ll end up with debris that gets past the filter back into your pool water.

Pro tip: There’s a maximum pressure reading label on the outside of the filter. Never let your filter exceed this level on the pressure gauge.

How does a cartridge filter system work?

A cartridge filter system works by drawing water into a tank that houses cylindrical cartridges of fine, pleated mesh material. The tight mesh filters out the impurities from the pool water. The cartridges are then simply removed and washed when needed to keep them clean and functional. Read on to learn how to rinse the filters.

source: https://www.swimmingpool.com/maintenance/pump&filter/cleaning-pool-filter-cartridges/