You might want to put your water down before reading this one.
"Are you taking all our water?"
As I fill my 2 quart pitcher to make tea for the day. "You do realize is comes from the tap, right?"
"Yeah, but isn't something like only 3% of the water in the world drinkable?"
"If I'm not mistaken, it all gets recycled at some point anyway, right?"
"I guess, the cycle of water. Yeah, but let's not talk about that."
I'm guessing he knew where I was headed with that, but let this be a lesson to you, you should probably shouldn't argue water consumption with someone who knows about how waste water treatment plants work and that odds are 3 or 4 people already drank this water once anyway.
As my environmental prof said "Ivory may be 99.4% pure...but sewage is actually better than 99.4% pure water, so think about that. And the closer you are to the equator, the more likely you're drinking something someone else already did."