Compare our chlorine spa shock to "Spa 56" Chlorinating Granules! Our spa chlorine is high quality, fast-dissolving granular chlorine. It is pH-neutral and leaves no residue. Use to regularly sanitize your spa or as a shock treatment for a quick chlorine burst. Powerful granular dichlor provides 56% available chlorine. Add directly to the water for immediate results. Sanitizer dosage rate: 2 oz. per 500 gallons.