There is probably a calcium buildup in the lines from the tank to the humidifier. You will need to take it apart to lean it. 50/50 White Vinegar should do the trick, Then flush the system with clean water, before using it as a humidifier again. In the future try using Bottled Spring Water or Distilled Water instead of tap water. Especially if your source of water is a well.
Answers & Comments
There is probably a calcium buildup in the lines from the tank to the humidifier. You will need to take it apart to lean it. 50/50 White Vinegar should do the trick, Then flush the system with clean water, before using it as a humidifier again. In the future try using Bottled Spring Water or Distilled Water instead of tap water. Especially if your source of water is a well.