Can A Clogged Vent Cause A Toilet To Overflow

Homeowners rarely think about areas of their home that are out of sight. Anytime you flush your toilet and watch the water go down the pipes, you think it was all done by the water in the tank that sits on top of the bowl. Also, most homeowners are unaware that a roof vent pipe is associated with their plumbing. It is amazing how the plumbing vent pipe works with your plumbing to assist in the flushing of waste. Can a clogged vent cause a toilet to overflow? Yes, a clogged vent pipe keeps air from getting into the plumbing system and prevents water flow.

Let’s take a look at what plumbing vents are and how they work.

A plumbing vent on a roof.

What Is A Plumbing Vent

An area that most homeowners forget about is the vents that exist on the top of their roof. There is a reason for each of the vent pipes to exit through your roof. Furthermore, they are relieving pressure in your home and allowing heat to escape from your clothes dryer or even gas or odors from the sewer line.

A plumbing vent pipe is no different as its sole purpose is to regulate air pressure in your plumbing system. As the plumbing vent pipe allows odors to escape and excess gas to be removed from the home, this venting system assists your toilets with flushing waste and water from the toilet bowl.

You will notice that the plumbing vent pipe is one of many vertical pipes poking out of your roof. It is attached to the drain line of your plumbing. Also, pipes are hollow so air is always present. The roof vent pipe allows the air to escape as the wastewater is flushed down the pipes. If the air had nowhere to go, it would create a clogged vent as the air would take up space in the pipe, not allow the water to be flushed, and cause the toilet to overflow.

How Will I Know

There are a few ways to tell if your plumbing vent pipe is clogged. Luckily for the homeowner, it is easy to troubleshoot so let’s take a look below at the top ways to tell if the plumbing vent is clogged.

  1. Sewer Smell – if you smell a strong odor coming from your toilet or sinks it is possible that your vent pipe is clogged. Additionally, the vent pipe is there to allow gasses and odors to escape so if the gases are coming back into the home, then this is a problem. Also, these gases are methane and can create a carbon monoxide poisoning situation so immediately call a plumber.
  2. Gurgling Toilet – gurgling noises coming from your toilet after you flush or from your sinks is a clear indication that your toilet vent pipe is clogged. Additionally, if the air isn’t allowed to escape it will stay in the plumbing lines and cause a gurgling sound as the water flows through the pipes and the air is released.
  3. Slow to Drain – a clogged roof vent pipe is one of the reasons for slow drain. While you are working to unclog the toilet, consider checking the roof vent pipe. If it is clogged, your toilet clogging is definitely a result.

Get The Clog Removed

If you experience any issues pertaining to an over-flowing toilet, always check the vent pipe. Waste buildup in your pipes is not always the main reason for a clog so keep in mind that a clogged vent pipe can create a bigger issue for you and your health.

Not only does a blocked vent pipe create backups and overflows. It will also allow toxic gasses back into your home. Immediately call on your local professionally licensed master plumber to take care of the plumbing issues

Other Recommended Maintenance

Determining if a clogged vent can cause a toilet to overflow, can be a good idea to understand where the toilet water actually goes. In addition, there are main drain lines that flow out to the sewer or septic tank system depending on what you have for your home.

Next, look into other appliances that might get clogged. All plumbing is connected. This could mean you will have issues unrelated to the toilets. It could be that the clog in your vent pipe is causing issues of backup in your other plumbing areas. A clogged dishwasher drain can also be an indicator of a clogged vent pipe. So go ahead and unclog your dishwasher drain and then inspect the roof vent pipe.

Lastly, if you have a well and septic tank system you can check it. Air could be getting into the system and this could reduce your plumbing’s ability to flush the waste.

If you smell sewer or hear a gurgling toilet, you will need to fix it.

When Should I Call A Professional

Trouble-shoot each scenario to make sure that you can solve the problem. Furthermore, hire a professionally licensed master plumber to assist with plumbing clogs. They will be able to conduct a full inspection of your plumbing system. At the same time, if you wait you will cause greater amounts of damage to your home. An overflowing toilet is not ideal as the water damage could bring on bigger issues in your bathroom.

Not sure who to call? Reach out to your local home inspection team. They can conduct a full home inspection, which includes a plumbing system inspection. Also, the home inspection team will refer you to a reputable professionally licensed master plumber for any repairs to your system.


A homeowner’s job is never dull. Homeowners rarely think about how often items in the home should be maintained. Always keep a list of when home maintenance is done and your plumbing system is no different. Having a clogged vent pipe can be caused by rodents, birds, or other environmental factors. Also, this could set your entire plumbing system into a tailspin. As a homeowner, you wouldn’t want that smell, or headache to deal with.

Lastly, call on your local home inspection team. They can make sure your plumbing system is in proper working condition. Twin State inspections will conduct a quality home inspection in the Twin State areas of VT and NH.