At HomeQuestionsAnswered, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

Learn more...

What is a Vent Stack?

Lori Kilchermann
Lori Kilchermann

A vent stack is used to filter gasses away from a home or business and is a crucial component in an indoor plumbing system. It typically runs inside of the walls of a structure and exits out of the roof. Most notably, they are used to vent sewer gas as well as to create an air supply to allow the drains and toilets to operate smoothly. The vent stack is a critical part of any building's design.

In order for the plumbing in any structure to drain properly, there must be a supply of air allowed to enter the system. If not for the vent stack, flushing a toilet or pulling the plug on a sink would be much like trying to empty a soda can quickly by turning it upside down. Without air, the soda sputters and empties in big gulps and surges.


By poking a hole in the bottom of the can, air enters and the soda is allowed to escape rapidly and in a smooth manner. The vent stack operates much in the same manner within a plumbing system. Air enters the system, and the fluids drain smoothly and rapidly. This is also why the vent stack is designed to exit the structure at a point that is well above any plumbing component.

Often, plumbing problems that are discovered are vent-stack related. Birds, bees, leaves and debris have been known to enter a vent stack and effectively plug it up. This creates a blockage of not only the air flow crucial to the proper draining of the plumbing system, but also to the escape of gasses. Sewer gasses then build up and begin to vent through the drains within the structure. These gasses are not only unpleasant to breathe and smell, they can cause illness and even death.

Most installers will place a cover or a cap onto the top of a vent stack. These are usually a screened cover or cap that allows the gas to escape and the air to enter without permitting other matter to enter the pipe. For a vent that does not have a cover already installed, caps and protective covers are readily available at most home improvement stores and can be installed with common hand tools.

The vent stack has allowed the use of indoor plumbing for centuries. Without it, homes and businesses alike would not be able to offer indoor plumbing. With a minimal amount of effort, the vent can be kept operational and functional for many years.

Discussion Comments


We had some remodeling work done to the inside of our home, and the contractor cut one of the vent stack pipes off (we have no idea why). Now we have sewer gas leaking into the house. What is the best way to piece the pipe together?


I have a vent stack cap with a screened cover. This is the best kind to have, in my opinion.

I had a friend who had her toilet worked on, and the plumber left a cap on top of the vent stack that did not have a screen. She didn't know this at first, but she noticed that it took a long time for her toilet to drain after he left.

After a few days, she checked out the vent stack and saw that the cap had been left on top. She removed it and replaced it with one with wire mesh, and this solved her problem.


I never knew that my sewer gases were escaping through a roof vent stack. I really had no idea there was a need for this until I read this article.

I'm really glad that someone thought of this when designing homes with indoor plumbing. Whoever came up with the concept probably saved lots of lives.

Post your comments
Forgot password?
    • Worker