Here’s where it gets personal. Are you a “I want the cleanest air possible” person? Or are you a “My humidifier should last forever” person? RO water leans more toward the first camp.
Many humidifier manufacturers actually recommend distilled or demineralized water—which is basically RO water’s cousin. Why? Because they assume you’ll do regular cleaning. The risk of corrosion is low if you clean weekly.
But if you’re lazy like me (no judgment, coffee is more important), tap water might be safer long-term. Tap water has buffers and minerals that keep it from eating your machine. It’s the “boring but reliable” friend.
What About Bacteria? The Sneaky Villain
Here’s a plot twist: pure water is a perfect breeding ground for bacteria. Without chlorine or other disinfectants, RO water is basically a sterile swimming pool for microbes. If you let it sit, it can get funky.
Don’t panic. This is true for any water left in a humidifier for days. The solution is boring but effective: empty the tank daily, and give it a vinegar scrub once a week. No shortcuts, sorry.
For what it’s worth, I use RO water in my ultrasonic humidifier. I’ve done it for two years now. No corrosion problems yet, but I also rinse it like a crazy person every three days. Your mileage may vary.
