How do you know if on a water pipe is open or closed a valve is closed?

To determine if a valve on a water pipe is open or closed, you can usually inspect the valve handle's position. If the handle is parallel to the pipe, the valve is typically open, allowing water flow. Conversely, if the handle is perpendicular to the pipe, the valve is closed, blocking the flow. Additionally, listening for water flow or checking for pressure changes can provide further confirmation.