SpaPure Spa Oxidizing Shock Over time, spa water can look dull and the chemicals in the water don鈥檛 work as well as they should. Use Spa Oxidizing Shock as a fast acting, quick dissolving, non-chlorinated oxidizing treatment. Benefits No predissolving necessary. Spa entry can occur shortly after adding it to the water. Made in the USA. Applications Apply to the spa while the water is circulating. Apply three tbs for every 250 gallons directly to the water. Typically add this product weekly or more frequently if the spa is used often.