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How To Vent A Toilet

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

The venting mechanism is an essential component of any toilet. This piece of plumbing, together with the P-trap, is what makes it possible to prevent sewage gases from escaping through the pipes and into the residence.

Moreover, it is the mechanism that assists the best function of toilet flushing, as its purpose is to keep the liquids and gases in the pipe system balanced.

So, for example, while liquids tend to settle and gases ascend, the venting mechanism balances that out and prevents several plumbing issues. 

However, not everyone knows how the ventilating system works or how to properly ventilate their toilets (see also ‘What Are Toilets Made Of?‘).

In case you are one of those people, then this article is a great way for you to learn everything about how to vent your toilet. So keep on reading and get all the answers!

Why Do Toilets Need Vents?

Your toilet is built with a lot of curves and very few harsh edges, and, following each flush, water collects in the toilet bowl. 

The water isn’t simply there to assist keep the toilet clean while you’re using it. It also functions as a means of ‘insulating’ the drainage system.

If there was no water to seal the drainage system, sewage gases would leak into your home through the piping system.

Now, as you can imagine, sewage gases are not at all pleasant; quite the contrary, they stink. 

Besides that bad odor, another reason why they are so undesirable is due to the fact that they can also pose threats to your overall health.

And if there’s something that goes without saying, it is that exposure to toxic gases might have long-term, negative consequences.

However, if the gases cannot enter your home, where do they escape from? The answer lies in the siphons.

Yes, it is the ventilating mechanism that draws them out of your toilet, preventing them from accumulating. 

As a result, it becomes obvious that there are many reasons why you need a vent. Here are some of the main reasons you should keep in mind:

The Vent Prevents Toilet Bubbling

Your toilet bubbling is a sign that something goes wrong with the plumbing system, as your toilet should not have running water or bubbles in the bowl at any time. 

While it might seem like a minor issue, bubbling releases all those unwanted toxins and gases in the air, so you should immediately take action and call your plumber. 

If there is flowing water, it is generally the result of a problem with the toilet tank instead of the ventilation system.

Bubbles in the toilet indicate that the liquid is not properly sealing the pipework.

Instead, air and other gases escape and rise through the water, and that is what might indicate that toxic gas is flowing into your property.

It Allows Proper Flushing

 The ventilation system in your toilet is critical to the flushing process. When the flushing system works properly, water quickly runs in the bowl and at high intensity, leaving it completely clean.

So, because the water running down the toilet is so heavy, it pushes through the P-trap on the vent and down the drain.

However, this procedure gets more challenging when the drain gets clogged (see also ‘ Drain Clogged With Hair: 5 Simple Tips To Dissolve it ‘).

When the drain is plugged, it takes more time to flush down, and a lack of enough airflow through ventilation might also impede the flushing process.

Beyond the P-trap, there is pressured air in the pipework. If it weren’t for the ventilation mechanism, every time we wanted to use the flushing system, a huge bubble would leap up from the toilet bowl, expelling gases out into the air.

The Vent Also Keeps The Water Level Constant

Did you know that the water level in your toilet bowl must be kept at the same level at all times?

If you did not know that and are now wondering why the answer is because it needs to be on the same level as the bottom of the P-trap (see also ‘S-trap VS P-trap‘).

If the ventilation mechanism is not properly adjusted, the air that is kept under the P-trap will either pull the water downwards or force it to go up.

As a result, water levels are unstable, and your toilet needs an expert to be fixed.

If you observe that the water in your toilet goes up and down quite often and is unstable, and you also see that it is bubbling, then you have a problem with the ventilation mechanism.

Toilet Venting Steps

To set up the ventilating system in your toilet, you must ensure that you follow all the construction rules that apply to your house.

The stages of setting the ventilation system up will differ based on how your toilet has been built, how long or short the pipes are, and what the regulations are in your region.

1. Tie To The Vent

The most typical design is for the drain pipe to be set behind the wall and then make a vertical turn to connect with the sewer.

A vent is built upward from the vertical drop and into the ceiling.

How To Vent A Toilet

This permits the toxic air to freely leave the house. Alternatively, a vent stack is another that can be used for a system like this one and can be connected with the help of a wye fitting.

2. Connect Under The Toilet

You can install your vent before the long-sweep elbow on the vertical part of your waste pipe.

Remember that not all waste pipes are equipped with long-sweep elbows, so this method will not work for everyone.

The best thing you can do is utilize a reducing wye with elbows placed to modify the direction of the vent as required.

3. Consider Using A Street Elbow And Wye 

Rather than utilizing the vertical section of the pipe, connect a wye to the horizontal section of the drain line.

The outlet can then be attached to a tilted street elbow. This elbow can be then vented vertically, allowing you to regulate the direction of the waste during its function.

Even though this design may appear a bit elaborate, it is quite simple to set up.

All you need is a reduction wye that will be used to connect a larger drain line to a 2” vent.

4. Opt For A Wet Venting Process 

You may also consider using wet venting, which basically means that you would have to connect your venting mechanism with another plumbing outlet or system.

This is a trick many people have taken advantage of not only to save time from installing the system but also to end up with more space in total.

And, if you are worried about it being illegal or wrong, let us reassure you by saying that it is permitted by both the International Plumbing Code and the Uniform Plumbing Code. 

What the wet venting system needs are pipes that can contain not just the water, but also the air that will go through them. Therefore, the minimum size you need for pipes are the ones that are 2”. 

As to where the system will connect, the answer is at the sink drain, as this draining system is linked to the toilet line with the help of a t-shaped sanitary pipe fitting. To use the plumbing term, you will need a decreasing sanitary tee.

If you are wondering whether this fitting is right for you and are intrigued by the idea of saving both time and space, you should definitely think about installing this system if your bathroom is small in size (see also our guide on best corner toilets for small bathrooms) .

What If I Don’t Have A Vent?

Some homes lack a venting pipe or have a defective venting line that is inoperable.

In that case, you can use the so-called “cheater vents” to build up your ventilating system. 

These “cheat” parts, known as air admittance valves, are not allowed everywhere so you should double-check that you have permission to use them before proceeding with their installation.

Air Admittance Valve To Vent Your Toilet

Air admittance valves let air into your drainage system while preventing sewage gases from escaping the drain and polluting the indoor atmosphere.

How To Vent A Toilet

Rather than needing a particular pipe, the air valves respond to the drainage mechanism installed and the air pressure they receive.

This means that to retain air inside the pipe, the seal shuts because of the pressure it receives thanks to gravity.

However, when the pressure drops, the seal can no longer remain shut, thus letting fresh air enter.

How To Install The Air Admittance Valve

The valve may be installed beneath your sink. It is also possible to link it to the sewer system.

The precise setup process will differ from one household to the other, as it depends on the type of valve your toilet needs, but usually, in the sanitary connection, an adaptor on a tee pipe will be required.

However, you should be given instructions and patterns that are specific to the model you are installing, so make sure you follow those step-by-step to get everything right.

Frequently Asked Questions

Is There An Optimal Distance For A Toilet Vent?

According to the UPC, a toilet vent should be no more than 6 feet away.

Can Toilets Self-Vent?

Some toilets have self-venting capabilities. However, you should follow all the regulations and make sure that the trap arm is vented one more time for safety.

Can My Toilet Overflow Due To A Clogged Vent?

Yes. In this scenario, plumbing pressure issues cause the water in the bowl to rise and overflow.

Is It Possible To Only Have One Vent For Your Shower, Sink, And Toilet?

If you want to save space, it is best to use a wet venting system.

The Bottom Line

We hope this article helped you figure out what the best venting system is for your toilet. Properly venting your toilet is critical for your health and safety.

If your toilet is bubbling or has variable water levels, it might indicate a problem with your venting system.

Therefore, make sure to always check the condition of your toilet to prevent your bathroom and house air from toxic gases and bad odors.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases. When it comes to dealing with clogged drains, many homeowners turn