Fast-acting spray and rinse formula with color spray indicator helps ensure complete coverage. Blue color spray indicator shows exactly what portion of the cartridge has been sprayed. Great to use when there isn"t time to properly soak a filter cartridge overnight. Quickly removes oil, grease and calcium from spa filters and hot tub filters. Monthly Cleaning Instructions: Remove cartridge filter element from filter housing and rinse thoroughly with water to remove loose material. Saturate the filter element with water. Spray Instant Cartridge Clean over entire surface area for maximum effect. Let set 3-6 minutes. Rinse filter completely with water and replace filter back into spa. (Note: If filter is not completely rinsed, foaming may occur.) For heavily soiled filters, repeat steps 1-5.