Installer wasn't aware and thus didn't have the 'drip / overflow pan' and his assistant had to go to a plumbing supply store to get one.

Second, the salesman didn't know (when I think he should have known) the width dimensions of the 'low-boy' drum style hot water heater; the hot water tank wouldn't fit through the closet door to the space where the tank is. And that caused a 90 minute delay in completing the job while the assistant installer went and got another, smaller tank that did fit.