The name water hammer sounds dramatic, doesn’t it? If you’ve ever experienced it, you’ll know there’s a reason for the drama. At the least, water hammer is an effectively descriptive name, because it sounds like a hammer striking against the pipes of your house.
Unless you have actual gremlins living in your walls who are smashing at your plumbing with miniature hammers, water hammer isn’t literal. The noise you hear is something that’s occurring inside the pipes. But it’s still not something you want to happen, and not just because it will make you jump around your own house at the abrupt noise. Water hammer can be damaging to the plumbing and to water-using appliances in the house.