How deep can fixtures be placed when they are combined?

When fixtures are combined, they must be installed at a minimum depth that considers various factors such as functionality, drainage requirements, and accessibility. The correct choice reflects the standard established for proper installation practices in Massachusetts plumbing codes and aligns with general plumbing guidelines that emphasize maintaining adequate heights for connections and ensuring proper wastewater flow.

The provision of allowing fixtures to be placed up to 6 inches deeper than another ensures that there is sufficient slope for drainage and prevents any potential backflow issues, which could arise if fixtures are installed at differing and excessive depths. This promotes effective waste removal and maintains a safe plumbing system that adheres to local regulations.

The other options suggest deeper combinations, which could compromise drainage efficiency and accessibility, potentially leading to complications in plumbing systems, such as improper flow and increased likelihood of blockages. Adhering to the 6-inch maximum depth for combined fixtures ensures that the plumbing system remains functional, efficient, and in compliance with applicable codes.