这些装置应具有永久性装置，以防止因反虹吸或反压力而产生回流。回流保护应至少包括两（2）个机构:一个用于防止反虹吸的进气口和一个用于防止反压回流的止回阀。这些装置是终端配件，可向软管接头供应饮用水，而不会有结冰的危险。

These devices shall have a permanent means to protect against backflow due to either backsiphonage or backpressure. The backflow protection shall include a minimum of two (2) mechanisms: an air inlet for preventing backsiphonage and a check valve for preventing backpressure backflow. These devices are terminal fittings that supply potable water to hose connections without danger of freezing.