just one caution--
do your utmost to not end a Water Fast in a "low" period, unless there are serious signs telling you to stop.
(these are rare)
A low is usually signifying a deep level of housecleaning, and is almost almost quickly followed by a high. This is why the elusive "fasting to completion" is so sought after. We all want to finish a fast with that reallygood feeling, despite any weakness. It is a state of complete (as much as is possible) housecleaning and says the body is now ready -fully- for vital nourishment.
My second longish (21 days) Water Fast I enjoyed my vegetable juice so much...the first one (ending on a low, at 29 days)all food tasted like cardboard for some time after. The body has its own 'time'.