No, I do not use peppermint water for upset stomach. I am happy to see that we have hubbers, such as "posts" who post good results with the use this remedy. I do use other Naturopathic remedies, with good results, for various signs and symptoms of gastro-intestinal discomfort. One must have some idea of what the cause of an upset stomach is if extreme signs and symptoms are present. For example, if one has an upset stomach with the vomiting up of red blood one must realize that a true surgical emergency may be present.
If one has an upset stomach, while at the same time experiencing bowl movements with red blood, or more importantly very dark (tar-colored) black stools, this is also a very extreme, that is medical emergency.
I bring the extreme cases to your attention to make you away that upset stomachs are usually benign, just troublesome problems, but on the rare occasion, they be the tip of the iceberg with more serious underlying problems at the source of the cause.
Regards, Dr. Haddox