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

The normal position of the liquid line service valve is back-seated. When a valve is back-seated, it means that the valve disc is in a position that allows fluid to flow through, while also enabling the valve to be removed or maintained without interrupting the system’s operation. This configuration provides both safety and ease of service for technicians, allowing them to conduct necessary repairs or inspections without needing to drain the system.

In contrast, a closed valve would prevent fluid flow entirely, which may hinder operation or maintenance. A fully open valve permits unrestricted flow but does not provide the same level of safety during service operations, as it can allow pressure release unexpectedly. A partially open valve may allow some flow but is not an ideal state for either operation or maintenance, as it could lead to inefficiencies or uncertainty in fluid dynamics. The back-seated position is preferred because it strikes a balance between operational efficiency and safety during servicing of the fire alarm system's liquid line.