Most U.S. jurisdictions now require bibcocks to have a vacuum breaker or backflow preventer, so that water cannot return through the bibcock from the hose.

Some plumbing codes require hose bibs to be equipped with a vacuum breaker.

Position the mounting flange so that the long sides are horizontal or tilt down about a quarter-inch on the side having the threaded connection and vacuum breaker for a garden hose.

Most plumbing codes now require outdoor sillcocks to have vacuum breakers.

A vacuum breaker typically contains a plastic disc that is pressed forward by water supply pressure, and covers small vent holes.

Vacuum relief valves are sometimes known as vacuum breakers.

Atmospheric vacuum breaker (AVB)

Operating without a vaild permit, flies, no vacuum breaker and hose-bib behind washer.

It also has a vacuum breaker, which prevents water in a garden hose from flowing backward into the rest of the household plumbing, possibly contaminating it.

No anti-backflow device or vacuum breaker, material on floor, mouse droppings, waste drains in sink, equipment greasy.