How to tell a Hot San Marco 1/4 turn valve from the Cold San Marco 1/4 turn valve
Its very simple to distinguish between the Hot and the Cold San Marco 1/4 turn valves:
The Hot Valve has a nick on every side of the nut whereas the Cold valve doesn’t.
More importantly though, Valves open clockwise and anticlockwise.
To open a Cold Valve you turn the Splines (at the top of the valve where the handle is placed) Anti-clockwise
Cold Valve opens Anti-Clockwise