Watts 0792093 3/4″ dual check valve this 3/4 inch hose bibb vacuum breaker is designed specifically for wall and yard hydrants to prevent the reverse flow of polluted water from entering into the potable water supply due to backsiphonage. It consists of lead free body construction, stainless steel working parts, a rubber diaphragm and disc, and a draining stem. It permits manual draining for freezing conditions. The maximum pressure is 125 psi (8.6 bar).