What does the Village of Niles require to prevent backflow and cross contamination? In order to be in compliance with the IEPA, the Village of Niles requires that a backflow protection device be installed and then tested annually. A backflow device can be installed inline to prevent "good" water from mixing with "bad" should a backflow occur. These installations can range from simple, like a hose bib vacuum breaker, to slightly more complex, like a reduced pressure assembly or double check assembly.