Where is a square junction permitted to be used on a drain?

A square junction is designed for specific applications where changes in direction of the drainage flow are required. In particular, it is permitted to be used in septic tanks because these structures are designed to contain waste and require secure and effective junctions to manage the flow of sewage and wastewater. The square junction allows for a smoother transition and proper alignment within the tank, ensuring that waste can be processed and directed appropriately without creating blockages or overly sharp angles that could impede flow.

In more standard drain applications, such as gravity drains or vent pipes, circular fittings are typically favored because they reduce the risk of blockages and improve flow efficiency. Likewise, the inlet of a sink often requires specific configurations that accommodate user convenience and are better served with other types of fittings to prevent clogs. Therefore, the square junction's use is specifically aligned with its function in septic tanks, where its design can optimize waste management effectively.