The filter media is the pleated paper inside of a cartridge filter that helps trap particulates and debris from hot tub water, so it does not go back in the spa water. It also traps oils and lotions, but this can also clog up the pores of the filter media. This means regular cleaning by hosing the filter off is needed. It is suggested to rinse off the cartridge filter of a hot tub every 2-4 weeks or so depending on use.
The core of the filter is the strong center part around where the filter media paper is wrapped.
A filter cleaning wand device which attaches to any garden hose, can help with the filter cleaning process by spraying more of the pleats evenly and not damaging the filter paper in the cartridge.
Filter Media Thickness
When it comes to pleated pool filters, there is some debate of the cost effectiveness of using 4 ounce filter media over the standard 3 ounce filter media. Filter media or paper is made from spunbound polyester and is referenced on weight per square yard. Most hot tub filter media is 3 ounce paper, but in pools, some cartridges use the 4 ounce type.
In any case, all OEM pool equipment manufacturers use the NSF (National Sanitation Foundation International) Standard 50 as the standard for testing pool and spa filters. Tensile strength of the filter is degraded when using a pressure washer on the filter paper and that causes the filter to fall apart faster than it would if using a softer filter wand or straight garden hose when cleaning the pleats.