Well, at my friends house awhile ago then his brothers bong was sitting around with water in it. He doesn't have to hide it though 'cause his dad smoked and was chill with it.

Also this chicks house who like has people over smoking and drinking all day then there was water in the bong.

So not everyone cleans it all the time. I mean, if your bong is out all day, why bother changing it every time you smoke?