The HTH Shock Treatment is a must-have for any pool owner looking to keep their pool water crystal clear and bacteria-free all season long. Made to increase chlorine levels, this shock treatment effectively kills and prevents bacteria and algae, ensuring that your pool water stays clear and ready for fun. Apply directly to your pool water as needed and test weekly to keep free available chlorine levels between 1 and 4ppm. This treatment is effective for all swimming pool types, including those with liners and Gunite pools, and saltwater pool systems. In just 24 hours, you'll see results! Each bag treats 13,500 gallons, and this package includes 15 1-lb bags of shock treatment. Plus, it won't fade vinyl pool liners.