What is the purpose of a plumbing arrestor and how does it prevent water hammer in a plumbing system?

A Plumbing arrestor is a device used to prevent water hammer in a plumbing system. Water hammer is a sudden increase in pressure caused by the rapid closing of a valve, which can lead to loud banging noises and potential damage to pipes. The purpose of a plumbing arrestor is to absorb the shock of the water flow and prevent it from causing damage. It does this by providing a cushion of air or gas that compresses when the water flow is suddenly stopped, reducing the pressure spike and preventing water hammer.