Understand the water requirement
EPA notes that ultrasonic and impeller units can disperse material from their water and recommends low-mineral water. Follow the requirements for the exact device.
Do not confuse the labels
Filtered, distilled and demineralized describe different treatments. Read what the water product or filter actually removes; a household filter is not automatically a low-mineral water supply.
Record changes
Keep notes on water source, refill frequency and visible residue when comparing your own experience. Stop using a damaged unit and consult the manufacturer when performance changes unexpectedly.