Bottled water is pretty stupid. Everyone knows this deep down, even if they insist on buying it. I must admit that if I'm out of the house and have to choose a soft drink, I do tend to pick water over Coke or something. However, there's no hiding the fact that drinking it in the home is pretty idiotic. If any of your acquaintances can't see this, then the fact that it is not particularly safe either might help to convince them. If that fails, you really should find the Marcus Brigstoke rant on the last series of the Now Show - the Podcast is still available!