Does a Septic Tank Need a Vent Pipe?

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Does A Septic Tank Need A Vent Pipe?

Septic tanks and systems aren’t overly complicated but they do come in different configurations, meaning people often have questions about what their septic system should include. Today we will specifically discuss septic tank vents since this was one of the questions I had when researching my new septic system.

So let’s start by answering the question, does a septic tank need a vent? Yes, your septic system and all sewage systems for that matter need a venting system to allow gases to escape the system avoiding dangerous build ups or airlocks to form.  Your Septic System should have 3 methods of pipe ventilation, Inlet & Outlet, Roof-Vent, & Yard Based Pipe Vents. 

Continue reading this article to find out why septic system ventilation is important and the different ways in which a properly installed and functioning system will vent-out gasses.

How a Septic System is Vented?

So we have already stated that all sewage systems need ventilation to help gasses escape as needed. However, we haven’t dug into what that looks like on a typical septic system.

Your septic system can be vented in several ways. Here they are:

Venting Method # 1: Inlet and Outlet Pipe Ventilation

The first way your septic system is ventilated is through the inlet and outlet pipes. The inlet pipe allows waste to flow from your house into the septic tank and the outlet pipe allows it to flow from the tank to the drainage field. These pipes, when clear, should allow gases to flow out into the drainage field.

Venting Method #2: The Vent Pipe in Your Roof

Roof-vent pipe

Have you ever wondered what those vent pipes coming out of your roof were? I know I did, actually, I thought they were some type of vent from the bathroom fan but turns out those venting pipes coming out of your roof are designed to pull septic system odors and gases away from your home.

Here is a great little video that explains why plumbing vent pipes on your roof are important.

Venting Method #3: Yard-Based Septic Vent Pipe
EPA Septic Tank

The yard-based septic vent usually looks like a capped piece of white PVC above the leach field. It may also look like a candy cane shaped pipe in your yard.  The purpose of this pipe is it works in concert with the roof vent pipe to allow the air pressure in the drain to equalize.  When water displaces air in the vent pipes, it needs to normalize.

What is a Septic Tank Vent For?

Ultimately your sewer or septic system vent pipes allows for equalization of air pressure, and as a place for septic-gases to exit the system safely. The gases are a normal byproduct of the bacteria that break down the waste in both a septic or sewer system.

These gases typically have a foul odor or rotten egg smell. The gasses escape through the vents and are carried away from your home or yard.

Why Does My Septic Vent Smell?

The bacteria in a septic tank are anaerobic meaning they work without oxygen from the air. The result of the of the anaerobic activity generates odors most commonly from the hydrogen sulfide gas emitted.

This can cause a rotten egg smell.  Sometimes the smell may only happen on occasion, in that case, it may be due to specific wind current pushing wind from roof-vents and not necessarily a plumbing problem.  These occasional downdrafts are enough to make your yard unpleasant and make you think there could be a bigger problem.

However, if the smell persists it may be indicative of a clog or problem with your septic system.

How do I stop my septic tank Vent from Smelling?

If the smell is coming from a downdraft off your roof vent then a simple solution may be to lengthen the plumbing vent and extend well above the roof line. This will allow the gas to escape with great distance from the roofline, making it hard for a downdraft to push the gas down towards the ground.

Sometimes a downdraft from neighboring trees can be averted by cutting the trees, but this can be costly.

Others have had success adding a charcoal filter to the top of the vent.  Make sure the filter doesn’t restrict air flow.

Other Vent Related Questions:

Why does my Septic Tank Vent have a Pipe in the yard?

The pipes in your yard may be a sewer or septic clean out. It allows easy access to check the system should there be a problem.

Here is a quick video showing you what one of these vent pipes in your yard might look like.

What is the right septic tank vent pipe height?

The height of your rooftop vent pipe is usually dictated by local plumbing and building codes. So make sure you check with your local inspector to find out what the proper height is for your city or town.

To cut down on the potential of downdraft odors, you probably want your vent to 1-2 feet above your roof line.

As for the inspection septic system access pipes in your yard, often the city inspectors need these pipes to be sticking out quite high for final inspection of the septic system, however when it is done, they can usually be cut down even to the ground.

What are Signs My Septic or Sewer Vents are Clogged?

Clogged Septic or Sewer vents are an often overlooked plumbing issue. If the sewer or septic vents on your roof become clogged they may cause various plumbing issues.

Remember these vents are essential in regulating air pressure in your system. Without proper air pressure in your plumbing system that allows air to flow freely, you could incur drainage issues.

Here are some of the signs that your septic or sewer system vents might be clogged:

  • Gurgling Noises: If you hear gurgling or see water bubbling in drains. Or you may hear gurgling noises in your toilet shortly after flushing. The gurgling can be caused by are escaping through the drain.  The air should be flowing up and out of the sewer/septic vents. But if it’s clogged it has nowhere to escape so it goes up through the drains.
  • Slow Drains: A single slow drain usually means there is a clog in that that sewer pipe. But if you are noticing slow drains throughout the house then it can be an indication that the septic/sewer vents are clogged.
  • Sewage odors: If you are noticing a foul odor coming from your drains or toilet then you might be smelling air backing up through the drains.

What do I do if Septic Tank Vent Pipe is Blocked?

Snow-Caused Blockage

If you just started noticing the symptoms of a clogged septic or sewer vent pipe and the roof is covered by snow. Usually occurs on a flat room. Then it might be an indication that the vent pipe is blocked by snow or ice.  This can cause all the same symptoms of any other type of more permanent blockage.

Remedy: You can try removing the snow from the vent pipe in the short term.  Then when the weather is a bit better, have a plumber extend the height of your vent pipe so it is less likely to occur in the future.

Debris Blockage of the Vent Pipe

Your vent pipe should be slightly angled to keep leaves and debrief from entering the pipe and causing a blockage. If it isn’t, then it is possible debris has entered the pipe and caused a blockage.

Remedy: Have your plumber come out and clean the pipe, they have a special grabber tool for this.  Then have them re-angle the vent pipe to keep it from happening again.

Sewage Clogs of the Vent

Sometimes clogs can happen in the sewer line right where the vent pipe meets the sewer line. These problems can occur from items like wet wipes or feminine hygiene products being flushed down the toilet.  Flushing this stuff in a septic or sewer system is NOT RECOMMEND.

Remedy: Your plumber may need to access the blockage from the roof vent and use an auger down through the system to push the blockage free.


Here is a video showing how to clean the vent stack on your roof.

I hope this article has helped explain why your septic tank system needs proper ventilation.  Also, I know I wasn’t aware of exactly what the septic vent pipes really looked like, hope I was able to answer that question for you today.

If you need to get your septic system serviced find a local professional in our state by state directory. Simply click your state below.