Swimming pool managers need to maintain a narrow pH [local] range, and thus are working on swimming pool chemistry. If the water is either too acidic or basic it can be unfit for swimming. Likewise certain pH ranges will permit algae growth which is highly undesirable in swimming pools. Keeping the water fit for swimmers means managing for water [local] quality or balance. See the table [local] for normal pool chemistry levels and the second table to determine if the saturation index Si will lead to a corrosive environment or lead to scaling and staining. Pool water chemistry. Use of the Langelier Index to Balance Pool Water