Check for signs of wear when removing the cartridge from the filter housing. See if the pleats are damaged. Any cracks or crevices will allow debris to pass through, and the debris will enter your pool directly (if they don't block the filtration system first). At the same time, look for signs of microbial growth on the filter. If there are signs of algae or bacteria in the filter cartridge, further cleaning is required to keep the pool water free of microorganisms. Soak the filter in a hydrochloric acid solution to 20 parts of water. Place the filter in the solution until there is no evidence of blistering. Be careful to avoid skin contact with hydrochloric acid and protect eyes from splashing.
Replace filter cartridge
If you are satisfied with the quality and performance of the existing filter, the easiest way to change the filter cartridge is to get exactly the same model. Most filter cartridges have part numbers on the end covers. Determine the brand and part number of the existing filter, and you should be able to order the exact water filter replacement cartridge.
If for some reason this is not an option, for example, if a brand of filter cartridge is no longer in use, or if you are not satisfied with the performance of the existing filter, you can also measure the size of the existing filter to find a suitable alternative. Measure the length and diameter of the filter cartridge. A reputable pool supply company can help you determine high quality replacement filter cartridges based on these sizes.
The replacement filter cartridge should be installed right back into the filter housing to replace the old filter cartridge. Do not force the filter in because doing so may damage it. If the filter is not easy to fit into the housing, you need to find a filter with a slightly different size. When the new cartridge is in place, the filter will be ready to run. Since you have replaced the cartridge, you should be able to enjoy months of clean water.