Actually, there's nothing wrong drinking bong water...

The problem comes from our "experiences" of bong water...

If you're going to drink bong water,
1- Ultra clean bong
2- Ash catcher after the bowl
3- good drinking water

There's quite some interesting stuff that gets left behind in bong waters... but when your best friend doesn't clean his bong for 3 weeks, it's definitely disgusting to even think about drinking bong water.