What makes flushing so different from the mainstream of cleaning processes? It is truly a unique process with subtleties that can make it difficult to develop. So what is flushing? Webster’s says it is to “cleanse with a rush of water.” From this simple definition the basic idea of a fluid moving across a surface to remove soils mechanically can be visualized. However, what is missing is the idea of enclosed, basically inaccessible surfaces that need to be cleaned. This goes beyond blind holes and slots to the fact that parts requiring flushing to clean internal surfaces are unable to utilize surface inspection to verify cleanliness. Thus, the process must be reliable.