Clorox pool spa ph. minus safely lowers ph. level of spa water. You need to maintain your spa water ph. levels and total alkalinity for the comfort and safety of users and for the other spa products to work properly. Use test strips or test kit to measure ph. The ideal ph. for spa water is between 7. 2 and 7. 6. Follow dosage chart on clorox pool spa ph. minus to adjust ph. as needed.