When we were kids my Mom told us that we were not supposed to drink the water from the tub, and we thought she meant that we could not drink the water from the tub faucet because it was bad for you. So for the longest time I thought the water that came out of the faucet was only to bath in not to drink.
A childhood belief about bathrooms

others believed things like this
- I thought tonic water was toxic water and wondered why would anyone drink it if it is toxic?— Dr.Badguy
- When I was young I refused to drink well water because I thought it came out of whales.— itodd
- My mum used to tell me that you couldn't drink water out of the tap from the bathroom as it was poisonous.Anon
- I used to think that if I ate a fruit seed it would grow in my stomach if I drink water after thatAnon
- if you drink water from unsafe places, frogs will grow in your stomach...— Olivier
- I thought that hydrogen was pure water (since I knew hydro- meant water) and H2O was impure some how— Hexetic