Trisodium Phosphate (TSP): Instead of a commercial filter cleaner, use 1 cup TSP to 5 gallons of water. Soak for a few hours. The use of biguanides in a hot tub instead of bromine or chlorine sanitizer will necessitate cleaning it off thoroughly before putting it into any kind of filter bath.
Spa, Hot Tub or Swimming Pool Filter Cartridge Cleaning Instructions and. of TSP(Tri-Sodium Phosphate)*see definition below, with Five gallons of hot water.