Concerned daughter - Dad is dehydrated

My Dad was placed in a nursing home last week.

He is 80, and was in the hospital for a month after a fall in which he broke ribs, and fluid was accumulating in his chest cavity.

The Dr. at the nursing home said we might want to consider hospice.

They have determined that he is getting dehydrated, as he has no interest in eating or drinking.

How long does it take to die from dehydration in his current state?