20210331 15493000 1.0 TRUE Water Control Valves Control valves are shown from 1:4,800 to larger scales. The symbol for control valves may be rotated or changed to reflect the type of valve (butterfly, ball, etc.), or a box symbol may also be added when these values are installed within a box. The difference between control valves and system valves is that control valves have a backflow prevention control. Control valves are labeled at scales from 1:1,200 and larger with their asset ID.