What is the normal position of the liquid-line service valve?

The normal position of the liquid-line service valve is back-seated. This positioning is crucial for ensuring the safe and efficient operation of fire protection systems, specifically those utilizing liquid agents.

When the valve is back-seated, it allows for the service valve to be closed while still maintaining a connection to the system, which is essential for performing maintenance or inspection without shutting down the entire system. This position prevents leakage and ensures that the liquid agent remains ready for deployment in the event of a fire.

In contrast, if the valve were fully opened, it could lead to potential issues, such as unnoticed leaks or unintentional discharge of the liquid agent, which can be a safety hazard. The half-seated position would similarly not provide the necessary sealing to prevent leakage, and a closed position would prevent any maintenance from being conducted. Therefore, understanding the importance of the back-seated position aligns with best practices in managing fire alarm and suppression systems.