What is a stack vent?

A stack vent is specifically defined as a vertical vent that serves the soil waste stack, which is critical in plumbing systems. Its primary function is to allow for the escape of gasses that accumulate in the waste stack, while also maintaining proper atmospheric pressure within the system. This not only helps to prevent the backflow of sewer gases into the building but also ensures that waste can flow freely through the system by equalizing pressure.

The stack vent typically extends above the roofline, providing a pathway for these gases to dissipate safely into the atmosphere. It plays a vital role in maintaining the overall health and functionality of the plumbing system, allowing fixtures connected to the stack to drain properly without creating suction that might disrupt flow.

In contrast, the other options do not accurately reflect the definition or function of a stack vent. The main vertical pipe for water supply refers to the supply lines that deliver water to fixtures, while a type of drain pipe in basements pertains to drains used for managing water infiltration or waste in lower levels. Additionally, a separate entity from the drain stack for pressure equality might describe a vent system, but it lacks the specificity and defined role that a stack vent has in conjunction with the soil waste stack.