If you are going to be keeping a normal, active life for the duration, i would honestly consider doing a juice fast instead of a water fast. I would honestly do some research before doing either type of fast though. There are steps to take when starting the fast and ones to take when breaking it. Soups are not a good idea when breaking it. Juice is good, but small doses watered down (4oz.) every couple of hours that first day of breaking, then building up to a half orange or a bit of watermelon. It will take you in excess of 7 days to transition back to a full solid dietary intake.
i honestly would do a bit of reading on all of this though.