Depending on how much fecal matter stuck in your bowels & excess water in your cells, you could lose up to a pound a day on average, so 25-40 pounds could be expected - but don't think that'll be all fat. And unless you're willing to commit another couple months to a strict low calorie diet afterwards, it'll all come back and then some because your metabolism will drop and muscle mass will decrease. For some people it can take several months for their metabolism to re-stabilize after a prolonged fasting period.
Just the facts. Water Fasting is not a good tool for weight loss, plain and simple. I recommend abstaining from 'white foods': dairy, fat, wheat, rice & alcohol for several months, coupled with an exercise program for the results you're looking for.