Water is pouring out of our Aprilaire humidifier
Here is a diagram of that model from Aprilaire. The drain tube (#9 in the diagram) might be clogged. Look on page 11 section 9 for further instructions about the drain tube. Also, check the main water outlet where the tube connects to the bottom of the pan to make sure drainage isn't restricted. Check the pipe that the drain tube is connected to. It could be clogged as well.