A Pressure Vacuum Breaker (PVB)
is a type of backflow prevention device
,used to keep non-potable
(or contaminated) water from entering the water supply. A PVB is similar to an atmospheric vacuum breaker
(AVB), except that the PVB contains a spring-loaded poppet. This makes it acceptable for applications that are high hazard or where valves are downstream. Pressure vacuum breakers must be protected from freezing when installed outdoors. PVBs usually have test cocks, to which specially-calibrated gauges are attached, in order to ensure that they are functioning properly.
PVBs are manufactured by Watts, Febco, Zurn and other manufacturers. Backflow prevention devices such as PVBs are regulated by the International Plumbing Code, but may also be required by government regulations.