Water fasting for couple of days at time gets annoying. You are hungriest for first few days and possilby weaker as well.
Better think to rotate juice fasting with water or to do better intermittent like you do like FAST-5, EAT STOP eat, eating alternate days, Eating once a day, etc.
Water you might as well stay on after the first few days go by and hunger goes to zero then its easy to go 7,14,21 etc.