"Water hammer" does not occur while you are running the water. It occurs when you shut the faucet off too quickly, and even then it is a momentary thing. Under certain specific conditions you can get water hammer when you open a faucet too quickly, but it is a rare situation and requires very specific parameters for it to occur. In either case the hammer only occurs for a fraction of a second and then disappears. You have some other condition, but without being there to hear it and test all the possible causes we cannot help you solve it.