lots of people have gone to 20 days or more on water only...
and no, not on IV--at home, and withouht intervention; granted you must rest a lot)
Please look around, and search various posts--read the Natural Hygienists...
I did a 29 day water-only fast last summer--you can find my posts on this forum. Chris has done an extended water fast. Mouseclick has, Michael has, Fonty has
done several long fasts.
It's not magic, but it is a bit of a (natural) miracle.