My dads been having diarrhea for 3 days now 5x a day. is that bad or serious? i told him to get pepto bismol (bismuth subsalicylate)

Self-limited: Most causes of acute diarrhea (less than 3 weeks in duration) are self-limited and will resolve on their own without any specific treatment. Ensuring that one does not become dehydrated is the most important intervention. Use pedialyte, or other similar liquids to staty hydrated. The elderly are at risk especially if they are taking water-pills or have kidney, heart or liver diseases.

Monitor him: If he is not having fever or getting worse, I am less concerned. If he is getting worse or having high fever and not able to drink much fluid to keep up with the loss via diarrhea, he may need medical attention. If he used antibiotic(s) recently, he may have antibiotic-associated diarrhea/c. Dificile colitis which can be a nasty infections. So, have him seen if his symptoms worsening. Good luck.