Can drinking at least 3 bottles of water a day cause loose bowel movements?

Probably not...: When defining "normal" for most things in medicine, consider a bell curve. Regarding stool frequency, "normal" is anywhere from 3 movements a day to once every 3-4 days. The peak of the bell curve (ie. Most common) is the magic 1 movement a day that everyone thinks is "normal." the bristol stool scale can also be used to define "normal" stool texture. Your doctor can help find "your normal.".