Which type of water closet connection is permitted when using back to back water closets with a double sanitary tee?

In plumbing systems, when using back-to-back water closets with a double sanitary tee, the proper connection method involves a horizontal developed length connection. This type of connection utilizes horizontal pipes to effectively transport waste from both water closets into a common drainage system.

The configuration allows for efficient drainage while maintaining adequate airflow, which helps prevent issues such as siphoning and the buildup of sewer gases. Additionally, the horizontal approach mitigates the risk of clogs that could occur with more vertical arrangements.

Using a double sanitary tee in this manner ensures that both toilets can effectively route waste to the main drain line without causing backflow or insufficient drainage. This design is common in commercial and residential plumbing layouts where multiple fixtures are placed in close proximity to utilize space efficiently while ensuring the functionality of individual fixtures. Other connection methods may not provide the same level of reliability or efficiency under these specific circumstances.