I have a 2009 18.5". The water pan does indeed get veeeery close to the charcoal ring. Sometimes on an overnight minion cook the ring will be full, including a few lit and wood chunks on the top, and i have to arrange the charcoal in a bowl shape to keep the water pan from resting on top of the fuel (mainly the chunks of wood). Foiling the pan exacerbates the problem.
I've considered adding removable shims to the water pan "shelf" to raise the its height, as I rarely use the bottom grate.