This chapter consists of a number of case studies discussing actual pump problems with which the author has dealt over the years, or which are based on contributions from students or colleagues of the author. All of the case studies are based on historically accurate situations, though changes have been made in the identity of the pump owner, equipment manufacturers, and individuals involved, as well as some nonessential details of the cases, to preserve the confidentiality of event and the anonymity of the people and companies involved.