In Store Only Removes accumulated dirt and grease deposits in spa cartridges. Filter Clean removes dirt, scale, rust, body oils and cosmetic residue accumulated in reusable spa filter cartridges. Directions for use: Stop the spa and remove the cartridge(s). In a plastic pail, prepare a solution of 250mL of Filter clean in 5L of water. Place the cartridge upright into the pail, covered with solution. Allow to soak for about 5-6 hours, then remove cartridge from the solution. Start again for multiple cartridges. Rinse cartridge immediately with fresh water or let it soak in clean water. Let it dry. Replace and start the spa.