Water hammer arrestors are devices designed to absorb the shock waves created when water flow is suddenly stopped or changed in a plumbing system. This phenomenon, known as water hammer, can cause loud banging noises and potential damage to pipes and fixtures. The arrestor typically contains a sealed air chamber that compresses when water pressure surges, helping to cushion the impact. These devices are commonly installed near appliances like washing machines or dishwashers, where rapid water flow changes occur. By reducing the pressure spikes, water hammer arrestors help maintain the integrity of plumbing systems and ensure quieter operation.