What is Backflow?
Under normal conditions, positive pressure forces potable (drinkable) water through piping into non-potable water. Backflow occurs when this normal flow of water within a pipeline is reversed. This can occur in two different ways, referred to as backpressure and back-siphonage, detailed below.
Cross Connections Create the Potential For Contamination
A cross connection occurs any time a property receives water from a potable supply — the user of the water and the provider of the water are connected. If a backflow prevention device is not installed, or improperly installed, then contamination is a risk. Every property owner is thereby considered a risk and thereby susceptible to water shutoff if the legislated precautions are not taken.
Contamination Occurs in Two Different Ways
Under normal conditions the pressure downstream of the cross connection is less than the upstream pressure. However, if this relationship is reversed backpressure occurs and contaminants may enter the potable water supply.
Back-siphonage, the other way backflow occurs, means just what its name implies — negative pressure in the main water line causes reverse siphonage to pull contaminates from the non potable water supply of a property into the potable water supply.