Demineralization of water is the removal of essentially all inorganic salts by ion exchange. PFDs (Process Flow Diagrams) are graphical representations of a process, its constituent tasks, and their order. A PFD aids in process design brainstorming and communication. A detailed list of actions that form the process under study is required for the PFMEA methodology. The team can decide on the level of detail. More detail costs time, but it minimizes the likelihood of missing Failure Modes.