Most check valves are marked by which indicator showing the direction of unrestricted flow?

• A. Arrow on the Casting
• B. Tag on the switch handle
• C. Colored symbol on the handwheel
• D. Lettered sign

Answer: (A)

An arrow cast into the valve body shows the direction of unrestricted flow. This marker tells you which way fluid can move freely and aligns with how the valve is intended to operate—opening to permit forward flow and preventing reverse flow. The arrow is durable, always visible once installed, and doesn’t rely on external tags or handles that can be lost or obscured. Other markings like a tag on a handle, a colored symbol on a handwheel, or a separate sign aren’t standard indicators for check valves and wouldn’t reliably convey the forward-flow direction in the field.