What is the minimum size of an exterior sump pump vent line?

What is the minimum size of an exterior sump pump vent line?

• A. 1 inch
• B. 2 inches
• C. 3 inches
• D. 4 inches

Answer: (B)

Vent lines for a sump pump discharge must be large enough to admit air freely as water exits the pit. If the vent is too small, rapid discharge can create a partial vacuum in the line, which can hinder flow, cause backpressure, or even affect the pump’s ability to prime and run smoothly. A 2-inch diameter vent provides adequate airflow to relieve that pressure and prevents the vent from becoming a bottleneck. This ensures the system vents properly outdoors during heavy pumping without clogging or restriction, which is why two inches is used as the minimum for an exterior sump pump vent line.

Vent lines for a sump pump discharge must be large enough to admit air freely as water exits the pit. If the vent is too small, rapid discharge can create a partial vacuum in the line, which can hinder flow, cause backpressure, or even affect the pump’s ability to prime and run smoothly. A 2-inch diameter vent provides adequate airflow to relieve that pressure and prevents the vent from becoming a bottleneck. This ensures the system vents properly outdoors during heavy pumping without clogging or restriction, which is why two inches is used as the minimum for an exterior sump pump vent line.