It depends on how many people are using the pool, how hot outside it is, and if the pool is in the sun. These are all situations where the bleach will break down faster and why you may need to add more bleach. By testing the water with the pool chlorine test kit, you will know if the available chlorine in the pool is too low, and that’s when you would add more bleach. You want to maintain the pool chlorine level between 0.5–1 ppm available chlorine as measured by a test kit.