How Do I Find My Plumbing Vent Stack? (Explained)

You’ve just found out that you need to clear your plumbing vent stack. Or, maybe you’re renovating and need to find the vent stack so that you can plumb your new fixtures properly.

The good news is, it’s not hard at all to find these things if you know what to look for. In this article, we’ll show you how to find your plumbing vent stack and why it’s important for any home improvement project involving plumbing or HVAC systems. Let’s get started!

How to Vent Plumbing
Key Takeaways
Plumbing vents are essential for maintaining proper pressure and preventing sewage gas from entering your home.
Plumbing vents are typically located on the roof of your home, near where your main drain line exits the house.
If you suspect a clogged plumbing vent, it’s best to call a professional plumber to prevent further damage.
While it’s possible to install plumbing vents yourself, it’s best to hire a professional plumber for the job if you’re not experienced.
Drain venting is an essential part of your home’s plumbing system and helps regulate water flow and prevent clogs.

Plumbing Stacks

A plumbing stack is a pipe that takes water from the toilet, bathroom or kitchen sink to the roof. It is called a stack because it stacks up the pipes. 

This vertical pipe connects to the roof of your home and helps prevent bad smells from coming back inside your house.

If you’re building an addition onto your house, it’s important that you don’t disturb this pipe when doing so. If you do, then there may be issues with drainage in other parts of your home once everything is finished!

Looking for plumbing blueprints for your house? Don’t worry, we have got you covered. Check out our guide on how to find plumbing blueprints and learn some pro tips to get your hands on them easily.

Vent Stack

A vent stack is a pipe that carries air from the plumbing drain to the outdoors. It’s usually located in or near an exterior wall, and it’s usually about 6 inches in diameter.

It can be found in your attic or basement, but not always directly next to the plumbing drain itself.

Vent Stack Characteristics

LocationUsually located in or near an exterior wall.
FunctionCarries air from the plumbing drain to the outdoors.
DiameterTypically about 6 inches in diameter.
MaterialTypically made of cast iron, PVC, or copper.
MaintenanceShould be inspected regularly to ensure proper function and prevent possible clogs.

Trap Vent

A trap vent is a pipe that runs from the drain at the bottom of the sink or tub to the main stack, which is usually located near the roof. The trap vent can be found anywhere in your home.

When you go to locate your plumbing vent stack, you’ll want to start with an inspection of your plumbing fixtures, specifically toilets and sinks. 

Look for pipes coming out of these fixtures that don’t connect with any other pipes. If you find such a pipe, it’s likely that it leads directly into your main stack (and if there aren’t any other connections after it goes through this pipe then you’ve found it!).

Running plumbing pipes through your house can seem daunting, but it doesn’t need to be. Check out our guide on how to run plumbing pipes to get some great tips and tricks to get it done right.

Venting System

The venting system is a series of pipes that carry water from the roof to the ground. These pipes are usually located near the roof and in a closet or attic. 

Venting systems can be made from plastic, metal, or PVC pipe. If you are replacing your old vent stack with a new one, then choose one that matches your current plumbing vent stack.

How To Find A Plumbing Vent Stack

To find your vent stack, start by locating the water pipes. From there, trace them to the roof, and check for any vents on the roof. 

If you don’t see any vents there, go back inside and check for vents in the basement ceiling and cupboards/closet ceilings.

Once you’ve determined that there are no visible vents in these areas, look at the interior ceilings of each floor especially those with bedrooms or bathrooms attached to them (soil stacks tend to be located near these spaces). If none of these things gives you results, then it’s possible that no soil stack exists.

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Check The Roof Of Your Home

To find your vent stack, look for a pipe that is connected to the roof of your home. The pipe may be connected to a chimney or to the top of a wall. 

It also could be connected on the side of a wall, in which case it will often have some kind of elbow joint on it (see photo). 

If you can’t find this pipe in these places, check with someone who knows about plumbing. They may be able to help you identify it if they’ve seen one like it before!

Finding Your Vent Stack on the Roof

LocationConnected to the roof of your home.
AppearanceAppears as a pipe extending above the roofline.
ConnectionMay be connected to a chimney or to the top of a wall.
DiameterTypically similar in diameter to the plumbing vent, around 3-4 inches wide.
MaterialOften made of cast iron, PVC, or galvanized steel.

Examine The Top Floor Interior Ceiling

  • Examine the top floor interior ceiling.
  • If you have a basement, try to look in there first as well.
  • Look for vent stacks that have been sealed shut with caulk or tape and look for vent stacks that are disconnected from your home’s plumbing system.
  • Examine the interior of your home for any sign of water damage such as mold or mildew where a vent stack might be located at ground level outside of your home.

Are you working on a DIY plumbing project and need to know more about right-angle plumbing pipes? Check out our guide on what is a right-angle plumbing pipe to learn more about this type of pipe and how to use it correctly.

Inspect The Basement Ceiling

Inspect the basement ceiling. Look for a pipe that is not connected to a water heater or furnace. If you find one, chances are it’s your vent stack!

Make sure it’s not connected to the main water line that runs through your home. This would be a sign of an old well-vented system, which has been replaced by most modern homes with city water supply lines going directly into houses without groundwater wells (a good thing). 

The exception is if you live in an area where people still use groundwater wells and have their own private wells instead of municipal sewer systems; these systems still need vented stacks as they did back when they were old-fashioned ways folks survived without having indoor plumbing at all!

The same goes for connecting pipes leading up from furnace/boiler heaters—these aren’t vent stacks unless they lead outside somewhere (and even then they might simply be air vents). 

If yours connect inside walls near each other, then it could just mean someone installed new ones alongside older ones but didn’t want to remove the older ones because they were trying to save money (or weren’t aware how important removing them was). Either way: not ideal!

Look Inside Closets And Cupboards

If you’re still not sure where your vent stack is, check out some other possibilities. If you have a utility closet or cupboard, look for a pipe that’s larger than the rest. You may be able to find it inside closets and cabinets if they contain plumbing fixtures like sinks or toilets.

If that doesn’t work and you can’t find a vent stack in an attic or basement, call a professional plumber who will come out to inspect the area for leaks or blockages.

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Trace The Water Pipes On Interior Walls

Trace the water pipes on interior walls. If you know where the drain and vent pipes are, you can trace them to their point of origin. 

Water pipes usually originate in a basement or first floor wall, so this is likely to be your best starting point. 

If you have an older home with galvanized iron pipe, look for traces of rust near where it enters the walls—this will indicate that there was once a vent stack here!

Trace Discharge Pipes From Toilets And Sinks To Their Source

If you’re looking for a toilet’s discharge pipe or sink waste lines, follow them back down through their respective fixtures until they meet each other at the P-trap under each fixture (or just trace them directly up from underneath). 

This will give you an idea of how far apart these fixtures are from one another and therefore where they should be located relative to one another (likewise for drain lines).


If you can’t find it, then you probably don’t have one. If this is the case, then there may be some other issue that can be resolved on your own without calling a professional plumber. 

For example, if your vent stack is missing and water is leaking into your basement, then you should contact an expert immediately because it could lead to mold or even structural damage. You may also need a new garbage disposal unit installed if maintenance hasn’t been performed recently.

Further Reading

For further information on locating plumbing vents and other plumbing-related topics, check out these resources:

How to Locate Plumbing Vents: This article provides step-by-step instructions for finding plumbing vents in your home.

Learn About Plumbing Vents: This resource from American Home Shield covers the basics of plumbing vents, including why they’re important and how they work.

All About Drain Venting: This article from Better Homes & Gardens provides an overview of drain venting and how it relates to your home’s plumbing system.


What is a plumbing vent?

A plumbing vent is a pipe that connects to your home’s plumbing system and allows air to enter the system, preventing a vacuum effect that can impede the flow of water.

How do I locate my plumbing vents?

Plumbing vents are typically located on the roof of your home, near where your main drain line exits the house. Look for pipes extending from the roof that are about 3-4 inches in diameter.

How important is proper venting in a plumbing system?

Proper venting is crucial to your home’s plumbing system, as it helps maintain proper pressure and prevent sewage gas from entering your home. Without proper venting, you may experience slow draining, clogs, or even sewer odors in your home.

Can I install new plumbing vents myself?

While it’s possible to install new plumbing vents yourself, it’s not a task for beginners. It requires cutting into your home’s plumbing system and working on your roof, so it’s best to hire a professional plumber for the job.

What are some signs of a clogged plumbing vent?

If you have a clogged plumbing vent, you may experience slow draining, gurgling sounds in your pipes, and even sewage backups in your home’s drains. If you suspect a clog, it’s best to call a plumber right away to prevent further damage.