My first fast was ten days followed a few weeks later with a more confident 30 day fast. Both were with only one glass of water a day, a compromise between the dry fasting I had read about and wanting to stay alive! ;) Unfortunately the information I had didn't include details of the fast after 7 days- so I wasn't sure how much water to have after seven days and decided to go the whole way through with only a glass a day. That amount of water was barely enough to wet my throat, and did little to relieve the symptoms of a dry fast which were constant indigestion, aching muscles, dizziness and an absolutely disgusting taste in my mouth and throat!
Drinking so much water is like having a buffer against those symptoms. :)