Drinking too much water and having a stomach ache may be an adverse reaction to drinking water, or you may be suffering from a digestive disease such as gastritis or gastric ulcer. 1. Adverse reaction after drinking water: If you drink too much water at once, or the water temperature is relatively cool, it may stimulate the stomach and intestines to cause discomfort, such as abdominal distension, abdominal pain, etc., and in severe cases, it will cause diarrhea. 2. Gastritis: the gastric mucosa is repeatedly stimulated by inflammation, and the symptoms will be significantly aggravated after eating, drinking too much water at once will increase the burden on the stomach and intestines, and the pain will be more intense. 3. Gastric ulcer: gastric ulcer itself can cause stomach pain, not pay attention to a reasonable diet during the disease or long-term fasting spicy, stimulating food, drinking too much water, will lead to pain aggravation, and accompanied by diarrhea, abdominal distension and other symptoms. Drinking too much water stomach pain, it is recommended to rest and regular observation, if the stomach pain has been, the symptoms can not be relieved, and then promptly seek medical attention.