Product review (5 stars): Easily Installed
The humidifier red light was blinking 6 times and the water was flowing continuously, so time for a new solenoid valve.

Don't be intimidated by this repair. I'm not much of a handyman but this solenoid valve was very easy to install. Drain the unit, unplug the humidifier, turn off the water, slip out the water feed and drain lines, take off the (drained) water tank, then lift the unit off the mounting bracket (see below). Remove one screw to take off the cover. Disconnect the solenoid clip on plug from the circuit board. Use a screw driver to release the four pressure clips that hold the back on. That exposes the valve; pop off the one remaining water hose. You can then slide the solenoid valve out of the frame. Reverse all this to put in the new one. The directions I just typed out are so lengthy that they make this repair seem more difficult than it is: as I said, I'm no handyman but this took under 15 minutes -- and I went very deliberately.

The most difficult part for me was removing the unit from the mounting bracket. It took me a bit to discover that the bracket has a piece of metal that protrudes and acts as a lock to prevent accidental removal of the unit. That piece of metal is clearly visible in the Honeywell video on Youtube on how to install the unit, but the video never mentions its function. As you look at the bracket, it's on the left. It doesn't hurt to look at this video before changing the solenoid valve, and it probably will make you more comfortable about taking the unit off the mount and reinstalling it.