This standard applies only to those devices classified as Vacuum Breakers, Hose Connection Type, which are designed to be installed on the discharge side of the hose bibb, hydrant or faucet which is fitted with hose threads. The design embraces a check valve member force loaded, or biased, to a closed position, and an atmospheric vent valve, force loaded, or biased, to an open position when the device is not under pressure. This device shall not be subjected to continuous pressure. Continuous pressure shall mean twelve (12) hours use in a twenty-four (24) hour period. Mechanical means used to defeat the vacuum breaker shall not be used. This device shall only be used on systems where the only source of low head back pressure comes from an elevated hose equal to or less than three (3.0) meters (10 feet) in height.