What type of fittings must be installed in fixture tailpieces receiving discharge from food waste disposal units or dishwashers?

Installing directional type branch fittings in fixture tailpieces that receive discharge from food waste disposal units or dishwashers is crucial for maintaining the proper flow of wastewater. These fittings are designed to divert the flow of water and waste at an angle, ensuring that it can efficiently enter the drain system without causing blockages or backflow issues.

Using directional branch fittings helps to manage the dynamic forces created by the discharge from devices like food waste disposals, which can generate vigorous water currents mixed with food particles. This design helps to minimize turbulence and allows for a smoother transition of waste into the plumbing system, which is essential for maintaining effective drainage and sanitation.

Other fitting types such as elbow or straight fittings may not provide the same level of efficiency for these applications due to their geometric design, which could lead to potential clogs or inadequate drainage. Reducing fittings are typically used to change the diameter of the pipe rather than effectively directing the flow, making them unsuitable for this specific purpose as well.