You need to check the pool water's pH to make sure it is between 7 and 7.6. If it's above or below that, you need to add the appropriate chemicals to return the water's pH to this range. Let's see what you know about keeping up your pool! (1) What is pH, what do you use to test it, and why would it be important to keep the pH of swimming-pool water between 7 and 7.6? * Your answer