Do vent stacks matter? Boston plumbers decide
How important are drainage vent stacks, and what is their purpose?
— Angie's List member Michael Shadoan
Vent stacks are very important because they vent methane gas and allow air and water to flow through indoor plumbing to keep it running smoothly, says Steve Lamb, manager of highly rated Baker-Elman Plumbing Co. in Newton Center, Mass., which services Boston's metro west area. "Vent stacks are required on all legal plumbing systems," he says.
Michael Allen, owner of highly rated Allen Plumbing & Heating Inc. in Somerville, Mass., says a vent stack operates similarly to how a plastic straw operates when you place your fingertip over the end. The blocked end creates a vacuum and you can pull liquid out with it. When you remove your fingertip, air rushes in and liquid flows out.
With Boston's cold winters, Allen says, a vent stack might also experience "frost closure," which results when warm moist air passes through the vent, and then condenses and freezes on the walls of the vent pipe. In a prolonged spell of cold weather, frost buildup can close off the top of the vent, he says.
Lamb says vent stacks don't clog unless they are plumbed incorrectly. Allen agrees: "Vents are usually maintenance free - unless there's a problem with them, there's nothing you can do."
Drains that gurgle or emit sewer gas odors are good indicators that repairs or replacement may be needed, both plumbers say. Costs to repair vary, depending on materials needed.