That's like drinking out of a toilet or urinal though, unless you don't pee in the shower and you're a liar if you "don't".
On a more serious note, get a camping/backpacking water filter. It can come in handy even if you're not an outdoors type.
My highjacked thread just got about 5 miles longer. I checked notifications and scrolled up from @Grimbli's post and was like who the fuck posted all these huge drink pictures and then my comment came into view and I died laughing.