I swear to God I should be a plumber.

I did some more reading on water hammer. There are little air pockets in the pipes that act as cushions (since air compresses) and dampen the shock when you turn the water off suddenly. These air spaces can fill with water over time, so they stop working. The solution to try is to turn off the water main, empty the whole house of water (thus recreating the air pockets), and turn the water back on again. I did this. And it worked. No more banging pipes.

I hate plumbers.

Ok, I'm done with that now. I did feel incredibly manly turning the hot water on and off, though, and listening to the not-sound of it all.