Remove cartridge(s) from your spa filter and hose off with water to remove loose debris. Fill a clean plastic container, bucket, pail or garbage can with 4 gallons of water. Empty the contents of the HTH Filter Cleaner bottle into the water to create the cleaning solution. Place the cartridge(s) upright in the solution and soak for 3 to 6 hours or overnight. Remove cartridges(s) from the solution, hose off and replace in your spa filter. HTH 16-oz Low Odor Spa and Hot Tub Chemical Filter Cleaner Spa | 86123