What is the required height for a lavatory drain outlet above the finished floor?

The required height for a lavatory drain outlet above the finished floor is specified in the Massachusetts Plumbing Code to ensure proper drainage and functionality. The height of 18 to 20 inches is typical because it allows for optimal connection with standard sink configurations while also accommodating the expected rise of wastewater. This range balances the needs of both the plumbing system and everyday use, as it allows for comfortable access without compromising the effectiveness of drainage.

Setting the drain outlet within the 18 to 20-inch range also helps to prevent potential issues such as clogs and backflow, as this height aligns well with the design of common lavatory fixtures and their accompanying plumbing arrangements. Ensuring that drains are installed at the proper height is critical for compliance with plumbing codes, promoting both safety and efficiency in residential and commercial environments.