2-in-1 Water Tester MeterA good chlorine and pH level keep bad bacteria at bay. If the pH goes up too high, chlorine's germ killing power drains. Chlorine can also get eaten up if a lot of nitrogen (from debris, puddles, sunscreen, or sweat) or other organic gets into the pool. When chlorine and pH levels go out of whack, it can lead to diarrhea and ear and skin infections. That's why it's best to test chlorine and pH levels regularly They can change day to day based on pool