So what about a scenario in which a thin stream of hot-but-not-boiling water is running down a character's back for an extended (5-15 minutes) period of time?
How hot could the water get without putting him into call-the-hospital-now territory? (Character is disinclined to seek outside medical help, and I don't want him dying just yet.) Could he develop a tolerance for the pain, or would that only happen in the case of serious nerve damage? Anything else to keep in mind?