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What Can Clog a Plumbing Vent

Plumbing vents are a simple yet crucial part of any plumbing system. However, their location and design may not always work in the system’s favor. There are many ways that a plumbing vent can become blocked due to its surrounding environment.

We will look at what kinds of things you are most likely to find stuck in your plumbing vent as well as nifty gadgets and techniques you can use to unclog your plumbing vent. If you’re afraid of heights, you may want to prepare yourself for this article.

Animals can nest in and on vents, creating blockages. They can also fall in and die inside the vents, causing clogs. Plant debris and foreign objects also have the potential to get into the plumbing vent and cause a clog.

Anything That Falls Into or Onto a Plumbing Vent

Technically, anything that enters the vent or falls across it can cause a blockage. This is a fairly wide range of things, and sometimes, these are one in a million occurrences. However, there are three common categories of items that clog plumbing vents.

Animal Related Blockages

Birds Nests

Usually, birds prefer to build a nest and lay their eggs in trees. However, with more and more developments occurring, birds are also taking to manmade structures for a secure location to raise their young.

One of these structures may be your plumbing vents, which can provide a secluded and protected spot for them to nest.

Unfortunately, the most effective way to clear blockages in such vents does require you to make your way to the roof (or sidewall) with a flashlight and a plumbing snake or hooked rod.

You will need to check if there are eggs or hatchlings in the nest already.

You can clear away the nest debris and, using your flashlight, look in the pipe for any other obstructions. If so, feed a plumbing snake (amazon link) or hooked rod down the pipeline and scrape out the debris.

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Alternatively, you could use a power hose to force the debris down (the vent leads to the sewer line, so it’s fine if water gets inside it.

If you are anxious about heights, it may be advisable to get in a professional like a plumber.

Nesting occurs mostly in the spring, so be sure to be ready to cover your vents with a wire mesh to prevent future nest development (you cannot cap them).

Animal Carcasses

Vents coming out of your home often attract small animals like rodents, possums, squirrels and snakes as they are warm, fragrant (although not to us!), and lead to water.

Sometimes, these critters can navigate their way out of your pipelines and land up surprising you in your toilet or basin. However, most often, once they enter the plumbing vents, they are unable to escape and they die.

Some birds of prey will also hide their kills from other animals scavenging for food and deposit the animal carcass in your open vent.

If you can see the carcass, you can feed a hooked rod and pull out the animal. If not, you can hire a scope and feed it through your pipelines to see where the animal carcass is.

If you cannot reach the animal, asking a professional may be a good option but it may be costly.

For a more cost-effective method, you can use powerful drain cleaners that can digest animal tissue. However, this option is not for the faint-hearted.

If you happen to stumble upon a live animal, a scavenger feeding off the trapped animal carcass, you may need to call animal control to handle this.

Plant Debris-Related Clogs

If you are lucky enough to be surrounded by a plethora of trees in your front or backyard, you also understand that although beautiful and serene, they do keep you busy.

Whether you are entering into fall, into pruning season, or just experienced a heavy storm, you are bound to be cleaning up plenty of scattered leaves, and other plant matter.

Unfortunately, the flawed design of most plumbing vents makes it easy for plant debris to enter and clog up the pipeline. Again, you would need to get onto the roof (or hire a professional) and clear away the obstruction.

Use a flashlight to see if there is any plant matter buildup within the pipeline. Use a plumbing snake to fish out the obstruction. Just remember, this will be a recurring matter, especially in windy seasons, unless you modify your vent.

You can place a fine mesh over the opening, but you may still get smaller plant matter entering your vent.

It may be worth attaching a short, curved pipe to the end of your current vent so that the opening end of the vent faces the roof tiles (example below). This will make it harder for anything to fall directly into the vent.

Plumbing vent illustration

With such a setup, however, you will still have to make sure that the opening of the pipe is the correct height above the roof.

Foreign Objects Cause Blockages

If you are situated in a family-orientated neighborhood or have kids of your own, you are bound to get a ball stuck on the roof at some point.

Some of these balls can, by chance, manage to make their way into your plumbing system. Strong winds can also bring in other debris or cause pieces of roof to break or fall in (provided the vent is positioned towards the lower end of the roof).

If it’s a soft ball, you may be able to use a plumbing snake to rip the jacket and eventually pull it up and out of the pipe.

You may be able to fish out other foreign objects with a pick stick (amazon link), allowing you to grip and pull out the object.

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To prevent this from occurring, you can either put a fine mesh over the vent opening or attach a short, curved pipe as mentioned before.

Why Plumbing Vent Clogs Are Bad

Plumbing vents, although simple, are crucial to maintaining the water pressure in your plumbing system.

Naturally, plumbing systems have a negative pressure and water moves slowly and may empty the standing water collected in your P-traps.

The venting system allows air to enter the plumbing system to equalize this pressure, keeping water in your P-traps.

The airflow in the system also allows for your toilets to flush. Air is sucked in to push the toilet water down, and the pressure causes air to be pushed out at the same time, equalizing. If your plumbing vent is blocked, you will have this constant negative pressure and water won’t flow effectively.

In addition, the vents provide a path for sewer fumes to flow out instead of escaping into your home or building up in the plumbing.

How to Tell a Plumbing Vent Is Clogged

  • Sewer smells – The negative pressure empties out the P-traps and the foul sewer gas can escape your drainpipes and fill your home.
  • Gurgling noises – As water passes down the drain a vacuum is created, and if there is no air from the vent to fill this vacuum, water passes slower and creates glug-glug or gurgling sounds.
  • Long draining time – Due to the unbalanced pressure, there is no free flow of water and drains take longer to clear.
  • Toilet bowl not flushing – This could be due to the tank not being able to fill up because of the slow water flow created by the negative pressure.

For more details, you can check out the full article on how to tell if a plumbing vent is clogged.


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