SpaPure pH Up increases the ph of water. In spas and hottubs, pH levels should be maintained between 7.2 and 7.6. When the pH lebels are lower than 7.2, water may be corrosive. Water below 7.2 will start to degrade spa plumbing and equipment. water may not be as comfortable for users to enjoy. This product is compatible with chlorine, bromine, biguanide, silver-mineral, and ozone-treated pools and spas.