What is the maximum vertical distance permitted between a fixture outlet and the trap weir?

The maximum vertical distance permitted between a fixture outlet and the trap weir is 24 inches. This provision is established to ensure that waste can flow smoothly from the fixture to the trap without risking the formation of a siphon or slow drainage, which can lead to clogs or backups. If the distance were to exceed this limit, it could create challenges in maintaining proper drainage and venting, which are critical components of a well-functioning plumbing system.

This height restriction helps to maintain an effective seal within the trap while also allowing the water flow from the fixture to the trap without difficulty. Allowing a greater vertical distance could impede the effective operation of the trap, potentially causing issues such as air locks or the inability to adequately evacuate waste. Ensuring compliance with this standard helps to enhance both the safety and functionality of plumbing systems in buildings.