The best way to prevent a backflow event is by maintaining an air-gap between the potable water supply pipeline and an open or non-pressure receiving vessel. The District requires inspection and approval from the Backflow Program office of an air-gap before it may be utilized for commercial purposes.
Backflow Prevention Devices
In many cases, however, an air-gap is not a practical solution. In those cases, backflow prevention devices must be installed to prevent the undesirable reversal of water flow or mixtures of water into the distribution pipes of the potable water supply. In these cases, one of the following devices is required: