Which joints are allowed for a drainage system when installed in the same trench as the water service?

The use of lead and oakum joints in drainage systems is permissible when installed in the same trench as water service. This is primarily due to the historical context and the properties of the materials. Lead and oakum joints provide a robust sealing capability, which is essential in ensuring that drainage systems remain leak-free and meet the rigorous health standards of plumbing.

Lead has been used for centuries in plumbing applications due to its malleability and resistance to corrosion, making it a suitable choice for joints, especially in conjunction with oakum, which acts as a packing material that fills gaps and further prevents leaks. This combination can effectively handle the pressures and conditions typically found in drainage systems.

Furthermore, specific codes or regulations may dictate certain types of materials and joints that can be used, particularly when it comes to ensuring the integrity of both water service and drainage systems. In this context, lead and oakum joints are acceptable, ensuring that they do not contaminate the water supply, which is a major concern in plumbing design and installation.

In contrast, other material combinations presented do not share the same historical validity or may not meet modern safety codes, particularly concerning cross-contamination and the requirements set forth in plumbing codes.