It depends on where you live. Where I live, the water is okay to drink, but the next town over has had a decent amount of mercury in their tap water for years and it's been suggested that you don't drink it. My snake gets plain old tap water, and her bowl gets cleaned every few days to a week. If I had a humidifier, I would use distilled water, only because if you don't it voids the warranty, but since I do it by hand, I use regular tap water for humidity as well.