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What is a Vent Stack?

What is a Vent Stack?

You may have seen a chimney-esque protrusion coming out of your roof and wondered, “What does that do?” The vent stack is a part of the plumbing system in your home. It's a vertical pipe that doesn’t carry any waste and its main purpose is to regulate air pressure throughout the areas of your home’s plumbing system. It is also called a plumbing vent, and it keeps gases and smells from remaining inside the septic system. It is a critical feature of any plumbing system because it increases the efficiency of the water flow through the pipes.

Vent stacks function to provide ventilation so gases won’t accumulate within the system. Instead, they are routed through the pipes leading out of your home’s roof, and the vent stacks maintain the water level inside the pipes that form the trap seal. Any odor in the home is an indicator that the vent stack isn’t working properly, but this rarely happens.

When repair work is needed (which is rare) some professionals will test the stack’s performance by introducing peppermint into the vent stack. This will help to identify areas where sewer gas is leaking into the home. Older homes may use copper, galvanized steel, or cast iron for their vent stacks, but newer homes will contain vent stacks made from PVC.

How Does a Vent Stack Work?

Per code, every building that has plumbing connections to a sewer must have at least one vent stack. The vent stack is also a central component that directs the fumes to the ventilation area on the roof. The vent stack also regulates the air pressure within the system, which is a critical component of preventing smelly air. All vent stacks are designed to use the most direct pathway to reach the open air. Vent stacks will typically run parallel to the stacks carrying waste. To make things more confusing: the vent stack will either extend through the roof, or it might be connected to a stack vent.

Vent Stacks vs. Stack Vents

Stack vents also share the same function as vent stacks in terms of ventilation, but the structure is slightly different. The stack vent is an extension of a particular area called the waste stack. This is also located on the most vertical portion of the roof. The stack vent is distinguished by the fact that it contains a direct connection with the outside air. The stack vent functions to vent the sewer gas and improve the efficiency of toilets and drains.

However, this only works when there is adequate airflow. To understand the basic difference, the stack vent is directly connected to outside air, and it is a physical extension of the waste or soil stack.

Bottom line: the stack vent is a vent that is located on top of a stack. The vent stack is exclusively used for ventilation of sewer gases and doesn’t come into direct contact with any waste. It’s easy to get these terms confused. Problems can occur in both vents when birds build nests in them, or other obstructions result in the restriction of airflow. It’s not a bad idea to have your vent stack or stack vent inspected annually.

The professional plumbers at Texas AC & Plumbing Specialist can help you with any of your plumbing concerns, repairs, or inspections. Contact us online or at (512) 580-7551 for an appointment!


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