The manufacturer states you can use tap water in these devices, but then goes on the disclaim that if you have water with minerals or hard water then white "dust" deposits can occur. Theses deposits are supposed to be noted and if seem, you are to change to filtered or distilled water or purchase one of their filter cartridges. These devices use very tiny holes to produce the mist you get out of them. It takes almost nothing to clog them. You should always use distilled water in these devices to prevent clogging. They also require very regular cleaning to stay clean and thus prevent them from becoming mold fountains. White vinegar and water should be used for cleaning. Avoid detergents as they can gum up the inner workings of the unit.