Final answer:
A basement branch drain connected with a "Y" fitting to a main drain may not require a separate vent if the system allows for proper venting through other means, depending on specific plumbing codes and system layout.
Step-by-step explanation:
The question seems to refer to plumbing and the requirements for a vent in a drainage system. In plumbing, when a basement branch drain connects to a main drain via a "Y" fitting (or wye), a separate bent or additional vent may not be required if the configuration allows for proper venting through other means.
This can occur if the main drain has adequate venting and the branch drain's connection is close enough to the main vent stack. Understanding the specific plumbing codes and the layout of the existing plumbing system is necessary to make an accurate determination.