Yes, it is possible for a toilet and sink to share the same vent in a plumbing system. This configuration is known as a common vent or a wet vent system. The purpose of a vent in a plumbing system is to allow air to enter the pipes, equalize pressure, and prevent the formation of vacuum or siphoning effects.
In a common vent setup, the drain pipes from both the toilet and the sink are connected to a single vertical vent pipe that extends through the roof or connects to an existing vent stack. The vent pipe provides the necessary ventilation for both fixtures, allowing proper drainage and preventing air pressure problems.
However, it's important to note that local building codes may have specific requirements regarding venting systems, including the size and configuration of vents. It's crucial to consult your local plumbing codes or a licensed plumber to ensure compliance with the regulations in your area.
Professional advice and guidance will help you determine the appropriate venting solution for your specific plumbing system, ensuring proper functionality and compliance with local codes.