This is an updated version of the "College of Product Knowledge" product training course introduced by PME's sister publication, Supply House Times, in 1979, taking an in-depth look at backflow preventers.
The category of products we'll be discussing here is sometimes called cross connection control devices. Cross connection refers to any linking between a potable water supply (one safe for drinking) and any source of non-potable water--or any other fluid--into a common system. Examples of cross connection piping arrangements include bypass hookups, jumper connections, removable sections, and swivel or changeover devices. The need for cross connection control goes beyond the simple prohibiting of improper hookups themselves; it commonly involves specifying and installing of protective devices to prevent the backflow of contaminated or polluted water supplies in the event that cross connections are (sometimes have to be) made. These products are required by code for plumbing installations today, including municipal water systems, food processing plants, medical facilities and many industrial applications.