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By adding more chemicals, you alter the total alkalinity, increase the number of total dissolved solids and create chloramines and bromamines, which are the leading cause of “spa itch.”
Langelier Index, was originally deigned for municipal water systems According to Langelier, spa water should have a sanitizer level of 3 parts per million, a pH of 7.4 to 7.6 and total alkalinity in the range of 60 to 80. Langelier looks easy enough on paper, and it works just fine for municipal water supplies where the water is only used once. The nightmare starts when one tries to maintain these balances with water that is kept over 100 degrees and used over and over