If you are not utilizing the backwash function, you must install a 1/2-inch plug in the backwash port.
Hand-tighten the head onto the tank until the O-ring makes solid contact, then tighten another 1/4 to 1/3 turn . Do not use the handle to tighten the head. Operational Maintenance Manual Backwashing Valves - SWT Manual Backwashing Tank Head
Some models include a dedicated position to isolate the tank for maintenance without stopping water flow to the rest of the facility. Installation Guidelines If you are not utilizing the backwash function,