You can monitor your pool's pH level with a testing kit. There are many kinds of testing kits available; however, most homeowner versions are either reagent kits or test-strips. Reagent kits aren't too difficult to use. You take a sample of pool water, then add liquids or tablets to it. The water changes color, indicating its chemical balance. Test-strips work differently. When you submerge them in the pool for a few seconds, dyes they contain cause them to change color. Next, match up the strip to a color chart to determine the pool's pH level. Use this information to gauge what kind and how much of the chemicals your pool needs.
Unless you are a licensed contractor experienced in pool draining in the Jacksonville, FL area it's highly unadvisable to drain your pool. As a general rule, it's best to leave water in a pool throughout the winter because the weight of the water counteracts with forces from the ground pressing up against the pool from below which can cause the pool to ``pop`` out of the ground.