Where should the main vent be installed in a one-pipe gravity return steam heating system?

In a one-pipe gravity return steam heating system, the ideal location for the main vent is 15-18 inches back from the end of the last steam-carrying main. Placing the main vent in this position allows for efficient air removal from the system, which is crucial for optimal performance and heating efficiency. When steam travels through the system, it displaces air that has accumulated in the pipes and radiators. If the vent is located too close to the end of the steam main, it could become ineffective in venting the air quickly enough to allow steam to circulate properly.

This placement ensures that the vent can effectively remove air from the entire system, facilitating better steam distribution and reducing the risk of issues like water hammer, poor heating, or uneven temperature distribution.

While vents can be installed in other areas of the system, positioning it correctly enhances the overall functionality and effectiveness of the steam heating system. The other options do not provide the same level of air removal efficiency needed for proper steam flow.