diagram illustrates a specific plumbing configuration known as wet venting. 

* Toilet: This is the standard toilet fixture.

* Basin: This refers to a sink or washbasin.

* Wet Vent: This is the crucial element in this setup. It's a vertical pipe (larger in size than a typical drain pipe) that receives both the drain from the basin and the vent for the toilet.

* Dry Vent: This is a separate vent pipe that provides additional ventilation to the drainage system.

* Stack Vent: This is a vertical vent pipe that extends above the highest fixture in the drainage system.

How it Works:

1. Wastewater Flow: When you flush the toilet, the wastewater flows down the toilet drain. 

2. Wet Vent Action: Simultaneously, water flowing from the basin also enters the wet vent. This water flow creates a seal or "water trap" within the wet vent, preventing sewer gases from rising back up into the toilet. 

3. Ventilation: The dry vent and the stack vent work together to provide adequate ventilation for the entire drainage system. The dry vent helps to equalize air pressure, while the stack vent allows sewer gases to escape safely into the atmosphere.

Advantages of Wet Venting:

* Space Saving: Wet venting can be more space-efficient than traditional venting systems, as it eliminates the need for separate vent pipes for each fixture.

* Cost-Effective: It can be less expensive to install than traditional venting systems.

Important Considerations:

* Plumbing Codes: Wet venting systems must comply with local plumbing codes and regulations.

* Fixture Placement: The placement of fixtures in relation to the wet vent is critical to ensure proper function.

In summary:

The diagram depicts a wet venting system, where a single vent pipe serves both a toilet and a basin. This configuration relies on the water flow from the basin to create a seal within the vent pipe, preventing sewer gases from entering the toilet. While efficient in terms of space and cost, it's essential to adhere to plumbing codes and ensure proper