Maples water

I have this water bottle that filters water and a couple days ago I decided to put in water from the fountain instead of tap water. The water was really foggy and even though I have a filtered water bottle, I didn't want to drink it. so I filled it up with tap water like I usually do and it was clear. Maybe our tap water is cleaner than our fountain water? Who knows. But id like to know if our fountain water is foggy because it's a chemical to clean the water, or if it's just dirty?