What is the restriction on using a double sanitary T fitting?

The use of a double sanitary T fitting has specific restrictions due to the way wastewater flows through plumbing systems. One of the primary restrictions is that it cannot connect trap arms of certain fixtures. This is primarily because the double sanitary T is designed for certain configurations of plumbing where specific drainage requirements must be met to avoid the risk of siphoning or creating blockages that can lead to backflow or improper drainage.

When connecting multiple fixtures, the design must ensure that each trap arm operates independently without interfering with other traps. If traps from incompatible fixtures are connected using a double sanitary T, it could lead to issues such as cross-contamination or hinder the drainage performance. This is crucial for maintaining proper sanitary conditions and ensuring that venting requirements are satisfied.

In contrast, the other options relate to different aspects and limitations of plumbing fittings that aren't applicable specifically to the double sanitary T's design and function. For instance, while there are limitations on connecting certain types of pipes and hydraulics through fittings, these do not bear the same emphasis as the potential complications arising from connecting various trap arms, which is directly linked to the fitting's purpose in drainage systems.