What is a Plumbing Stack? How to Fix a Clogged Vent Pipe?

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Plumbing stack or plumbing vent is a quintessential part of your home plumbing system, and you may not even be aware of it.

A vent? An air vent essential for the plumbing system? Yes, you read right.

If you’ve encountered gurgling sounds coming from after you flush your toilet, or you can smell strong, pungent odors in your bathroom or kitchen, you may need to check your plumbing stack.


Home Plumbing System 101 - Plumbing Stack

There are many important aspects of the home plumbing installation which work together and ensure smooth operating of said plumbing installation.

There are many smaller pipes that connect to the water fixtures in your home, such as a sink, a toilet, a bathtub, etc. These small pipes are oftentimes joined to a vertical drain pipe. This pipe is responsible for collecting all the wastewater from these fixtures to the main house drain. The wastewater then proceeds to the house sewer and so on.

In the process, the plumbing stack is of the utmost importance since it allows air into the pipes.

Part of the plumbing system in charge of handling wastewater is referred to as the DWV system – Drain, Waste, Vent system.

What Does DWV Do?

So, it's a three-part system:

  • Drain pipes collect the wastewater right from water fixtures.
  • A waste pipe is where all wastewater from the drain pipes meet and then travel to the treatment facility. This waste pipe is also known as the main drain pipe.
  • A vent pipe (plumbing stack) is in charge of distributing air so the water can flow through the main drain pipe without any restriction.

Moreover, besides allowing the air into pipes to ensure smooth wastewater flow, without gurgling and without creating a vacuum, the stack pipe serves as a "trapdoor". In other words, when dry, through this pipe, all of the toxic gasses and overall unpleasant smells escape.

Because of this, the plumbing stack goes through your roof. This may be why you never paid any attention to it before.


How to know if Your Plumbing Stack is clogged?

Of course, any segment of the plumbing system can become clogged due to various, different reasons, and the stack pipe is no exception to this rule. However, it must be noted that this is usually one of the more difficult issues that can happen.

The most common signs of clogged plumbing stack are:

  • Gurgling sounds: Due to the clogged pipe, air cannot escape up through the vent, therefore the only other option is through the drain of your sink
  • Slow drain: If only one water fixture is experiencing a slow drain, then the issue might be with the main drain pipe. Nevertheless, if all drains are slow, then it may be time to examine the plumbing stack.
  • Pungent gas odor: if there aren’t any apparent reasons as to why your bathroom is smelly – such as spills or something else, then it usually means that air is reversing back through the drains and into your home. This happens if the drainpipe pressure is too high and the plumbing drain traps that block the odors from returning to the bathroom cannot function properly.

And what are the causes?

  • Snow, leaves and other debris build-up: Get on the roof (carefully and mindfully, please), and inspect your plumbing stack. If it isn't curved at the top but is straight, then something may have fallen into the pipe. It not unusually for a bird or some other small animal to even make a nest inside. This is a very easy problem to fix.
  • Sewage clogs: if something other than human waste and toilet paper is thrown into the toilet, it may clog the sewer line exactly where it meets the plumbing vent.

How to Fix Clogged Plumbing Stacks?

Firstly, it must be emphasized that although, you may have all the necessary tools (which is highly unlikely, but not impossible), and think that it can’t hurt to try; we strongly advise that all of the reparations be done by a professional.

As mentioned above, leaf, snow, and any other debris are the easiest to fix. One of the ways you may try doing yourself is to insert a garden hose into the vent opening and turn on the water. The force will most usually clear any interference and obstruction.

If you opt for calling in a professional, a plumber will need a plumbing auger to access all the blocking debris. Additionally, he may replace your plumbing vent with a longer and curved one, to prevent this from happening again.

In addition to this, if the source of your problems is a clog in your sewer line, the plumber will also use a plumbing auger and push it down through the plumbing stack to grab onto the object and pull it out.

Although it is complicated to fix, it is very easy to prevent – just ensure that anything that is not supposed to be flushed is not flushed!


On the other hand, most of the plumbing stack reparations will require braking down walls i.e. searching for cleanouts. In an ideal condition, all of your house cleanouts are located on the outside, or only have items such as closets or shelves over it. But, since building codes vary from place to place, cleanouts in your house may be concealed by walls.

But, what is a cleanout?

As the name suggests, it helps with cleaning obstructed pipes. The plumber removes the cap from the cleanout and may firstly insert a camera to locate the blockage and then insert a snake auger to pull out the material.

The unclogging process for an experienced plumber is not so complex; it just varies from which place he will decide to deal with the issue.

Conclusion: How to Fix a Clogged Plumbing Stack

To conclude, we showed the most usual signs of a clogged plumbing stack and what causes it.

Although it looks (and smells) scary, for a skilled plumber equipped with modern tools the solving of problems shouldn’t prove too difficult.