What type of bend is typically used to connect a vent stack to a waste stack at the lower end?

The correct answer is the 1/8 bend (45 degrees). This type of bend is commonly used in plumbing to connect a vent stack to a waste stack at the lower end because it allows for a smooth transition with a slight angle that maintains proper flow. A 45-degree angle is beneficial because it reduces the likelihood of clogs by minimizing sharp turns, which can cause turbulence and impede the flow of air and waste.

Using a 1/4 bend (90 degrees) would create a sharper turn than desirable in this context; such a sharp angle can create resistance to airflow, which is crucial for effective venting.

A 1/2 bend (45 degrees) does not currently correspond to standard plumbing terminology, as standard fittings usually do not designate a half-bend option in this manner, making it somewhat ambiguous.

A straight connection could theoretically work, but doing so would not provide the necessary angle for optimal venting and drainage performance, which a 1/8 bend does. Therefore, utilizing a 1/8 bend is the best practice for ensuring efficient plumbing function in this scenario.