I live by the theory "one is none"

I Would pick up another so you have two. That way if one fails your not left in the dark.

I wouldn't trust the one you have. Pick up another and see if you need to mist.

Also the drinking water issue. I actually do it the opposite way. I give my snakes tap to drink and use filtered for foggers, misters, and misting. Tap will leave mineral deposits all over the tank glass but the spring won't when used for misting.