Where must fixtures be watertight when they come in contact with another surface?

Watertight conditions are essential in plumbing applications to prevent water damage, leaks, and mold growth. Fixtures must be watertight where they come in contact with floors and walls because these surfaces are typically where water can accumulate and spread if a leak occurs. Ensuring watertight seals at the junction of fixtures with floors helps prevent water from seeping into the building structure, leading to significant damage over time.

In residential construction, areas such as bathrooms, kitchens, and laundries commonly require plumbing fixtures—like sinks, bathtubs, and toilets—to be installed with watertight seals against walls and floors. This includes the use of appropriate caulking, adhesives, or other sealing materials to mitigate any potential leaks.

In contrast, the other options, such as watertight constraints at ceilings or specifically at windows, are less directly relevant to plumbing fixtures. Ceilings typically do not interact with plumbing installations in a way that necessitates a watertight seal, as plumbing fixtures are more engaged with the floors and walls where leaks are most critical. Windows, while requiring proper flashing and sealing to prevent water intrusion, do not relate directly to plumbing fixtures in the same way that walls and floors do.