The pH level of the water is one of the most important things to maintain to keep your spa healthy. If you do not maintain it, the water can damage your spa and become uncomfortable for people who use it. The ideal pH level is 7.2 to 7.8. If the pH level is below 7.2, your water is too acidic.
Test the spa's total alkalinity before testing and adjusting its pH level. If the alkalinity is not balanced, you cannot measure pH correctly. The alkalinity should read between 80 and 120 parts per million. If the pH level is low, your alkalinity reading may be slightly under 80. You can test the alkalinity with a spa test strip.
Add Spa Up if the alkalinity reading is low. Raise the alkalinity to the correct range before applying any pH chemicals. The main ingredient in Spa Up is sodium bicarbonate. Different brands are available, but all are commonly known as Spa Up or pH Up.
Determine how low the pH level is once you have checked and adjusted the alkalinity. Use a test strip to measure the pH.
Add Spa Up as directed on the label, depending on how low your pH reads. If your pH level is below 6.8, add three-quarters of a gallon of Spa Up to a 400-gallon spa. If it is in the 6.8 to 7.0 range, add a half gallon of Spa Up to a 400-gallon spa.
Add pH Balance once you have adjusted the alkalinity and pH levels to the correct range. Pour an entire one-quart bottle of pH Balance into the spa while the filter is running. It will maintain the pH level for at least three months.