When connecting weeping tile to the sanitary building drain, what must be installed?

When connecting weeping tile to the sanitary building drain, it is essential to install a backwater valve and trap. The backwater valve serves a critical function in preventing sewer backup into the weeping tile system, which could occur during periods of high rainfall or flooding. This scenario can result in the sanitary sewer overflowing and potentially allowing sewage to flow back into the weeping tile drainage system.

Incorporating a trap is equally important, as it helps to maintain a water seal that prevents gases from the sanitary sewer from entering the building. This is crucial for health and safety reasons, as sewer gases can be harmful if allowed to seep into interior spaces.

The other choices, while useful components in different contexts, do not specifically address the functionality and necessity of safeguarding the building from backflow and maintaining sanitary conditions when tying in drainage systems. Thus, the combination of a backwater valve and a trap is the appropriate solution for this plumbing scenario.