Abel and the Brain

Abel is called to a job where the temperature and pressure relief valve is releasing water during the night.  He does a pressure check and a test for thermal expansion and Indeed the system is being affected by thermal expansion.  

So Abel patiently explains to the gentleman how thermal expansion works and what causes it and how to rectify it.  The gentleman doesn’t quite “get it” and Abel explains it again, in simpler terms and still the man can’t follow it.  

“Look,” Abel says, “It’s not brain surgery…” and then he stops because the guy is really showing growing irritation.  “Did I say something wrong?” asks Abel.  

“I AM a brain surgeon!” the man says and then stomps into the house and sends his wife out to talk with him.