When fixture drains are common vented, where should the vent connection be made?

The correct connection point for the vent in common vented fixture drains is at the interconnection of the fixture drains. This location is crucial because it allows for proper ventilation of multiple fixtures while effectively managing the pressure and preventing the siphoning of traps.

When the vent is connected at the interconnection point, it ensures that any changes in pressure in the drainage system are equalized. This setup allows for the venting of both fixtures, leading to a reduction in the likelihood of trap siphonage and ensuring that wastewater can flow efficiently without creating negative pressure that could pull water from traps.

Additionally, venting in this manner complies with the codes for drainage systems as it optimizes airflow and maintains proper drainage function, which is essential for the health and safety of plumbing systems. Proper venting is key to avoiding issues such as odors and gas backflow, ensuring that the system operates efficiently and complies with the IRC guidelines.