Sioux Chief Hydra-Rester Boxed is a high-performance water hammer arrester designed to mitigate the effects of water hammer in plumbing systems. Water hammer occurs when a sudden change in water flow, such as quickly closing a valve, creates a pressure surge that can damage pipes and fixtures. The Hydra-Rester Boxed absorbs this shock, protecting your plumbing infrastructure. The HydraRester is ideal for installation in all domestic, commercial or industrial plumbing systems.