Safrax Dosage Guidelines for a Pool or Hot Tub: Easy to Use - Simply Add Tablets to Water! Add the proper dose of Safrax ClO2 tablets directly to the water. After adding the tablets, keep the pump running for a few minutes. For best results, add tablets after dark as chlorine dioxide is sensitive to UV light. Generally, it is advised to maintain 1 to 3 PPM in your pool/hot tub: • First Time Use: Use a dosage of 5 PPM when adding to OLD water. • Shock Treatment is from 5 PPM to 25 PPM. • If you u