The argument for peeing in the shower comes down to some quick math that shows that if you time your daily shower to coincide to one of your wees, you could save an astonishing 2,190 liters (579 gallons) of toilet water every year, or 699 billion liters (185 billion gallons) of water if the entire US joined you on your mission. That's a lot of water saved and would probably be a good thing for the planet.