Certified Pool Operator Practice Test

Having an ideal range of 200-400 ppm for Calcium Hardness in a pool is important because too little calcium can cause corrosion of pool surfaces and equipment, while too much calcium can lead to cloudy or scaling water. Option A, 150-250 ppm, may be too low and not provide enough protection for the pool. Options C and D, 400-600 ppm and 500-700 ppm, are both too high and can cause issues such as cloudy or scaling water. By maintaining the recommended range of 200-400 ppm, it ensures the proper balance for a pool's water chemistry.