If you thought pH was important, you were right. But, total alkalinity is even more important. The total alkalinity is the buffer of pH, if it is not balanced correctly, the pH will not give you a correct reading. Total alkalinity is the ability to control pH. Here is a simple way to understand the difference between pH and total alkalinity: Think of the pH as the thermometer on your furnace's thermostat. The thermometer measures the exact room temperature. If it's a little cooler than you like, you turn the thermostat up. You have just displayed the ability to control the temperature. Total alkalinity is like the thermostat, in that it gives you the ability to control pH. This is why you test and adjust the total alkalinity before even touching your pH test kit.
Your goal? To keep total alkalinity readings inside the acceptable range of 80 to 120 PPM. If you suspect your pH level to be a little high, then try for a higher reading of 150 PPM when testing the total alkalinity.
Why? Because pH-lowering chemicals will lower the total alkalinity as well. If your total alkalinity reading is below 80 PPM, then you will use Spa Up. If you got a reading above 120 PPM, then Spa Down is what you will use. Again, to achieve these readings you will need a test kit or test strips.
Now, you ask, what would happen if I didn't keep the total alkalinity balanced? Let's take a quick look at the problems that can result.