I recently fixed a leaking shower by replacing the cartridge in the handle. The leak is fixed, but now I have a banging noise when I turn the water on and off. I assume that when I turned off the water supply, drained the pipes to fix the shower, then turned the water supply back on, I somehow got water in the pipe that's supposed to have air to cushion the pressure. I have tried shutting off the water and draining the lines again, but can't get the noise to stop. Any ideas??