Will the Purest turn off when empty? January 23, 2019 19:34 Yes, the unit will automatically turn off when it's out of water. Related articles How long will the Purest Sleep Diffuser run before it runs out of water? How large of an area does the Purest Sleep Diffuser cover? How do I clean my Purest? Does the Purest Sleep Diffuser have a white noise option? Is Marpac Unplug made in the USA?