I've read that reverse ossmosis water is best. I've read distilled leetches minerals from the bones.
I've water fasted a few times - long fasts. I've read that if you don't get the toxins out they are reasorbed back into the body. Enemas or salt water flushes gets the toxins out. I rotate these two methods daily when fasting.
It's good to buy a book and read about fasting... there are too many important details that are missed otherwise. Such as, it is really important that the fast is broken correctly.