toilet venting

How To Vent A Toilet

The venting mechanism is an integral part of every toilet. Combined with the P-trap, this piece of plumbing is responsible for keeping sewer gases from venting through the pipes into the home.

It also allows you to flush the toilet properly.

The goal of the vent is to balance the liquids and gases in the piping system. When they’re left to their natural devices, liquids tend to settle while gases rise.

Why Do Toilets Need Vents?

Your toilet is designed with a huge number of curves and very few sharp edges. Water pools in the toilet bowl after each flush.

The water isn’t just meant to help keep the toilet clean when you do your business. It also seals the drainage system.

If there wasn’t water sealing the drainage system, gases from the sewer would flow through the pipes and into your house. Not only do these smell terrible, but they can also be bad for your physical health.

There can be long-term complications from exposure to noxious fumes.

But if the gases can’t rise into your house, they have to go somewhere. The vent siphons them out of your toilet so that they don’t build up explosively.

These are the main reasons you need a vent.

Prevents Toilet Bubbling

If your toilet is bubbling, there’s something wrong. Your toilet shouldn’t have constantly running water or bubbles rising in the bowl.

If there is running water, that’s usually an issue in the toilet tank rather than the ventilation system.

Bubbles in the toilet indicate that the liquid isn’t working to seal the plumbing as intended. Instead, air and other gases are escaping and bubbling up through the water.

That could mean that noxious gas is leaking into your home.

Allows Proper Flushing

Your toilet ventilation system is vital to your flushing. During a normal flush, water flows at a high pressure into the bowl.

Since the water is so heavy, it pushes past the vent’s P-trap and down the drain. When the drain is blocked, this process becomes more difficult.

Flushing takes longer when the drain is clogged. A lack of proper ventilation can also hinder the flushing.

The part of the plumbing system beyond the P-trap has pressurized air. If it wasn’t for the ventilation system, a giant bubble would burst up from the toilet bowl and release gases into the air every time you flushed.

Keeps The Water Level Constant

Did you know that the water level in your toilet bowl needs to be constant? It lines up with the bottom of your P-trap.

If the ventilation system isn’t calibrated properly, the air below the P-trap will either suck the water down or push it up higher. This leads to unbalanced water levels.

If you notice that the water level is rising and falling inconsistently, and that the toilet is bubbling, those are the two telltale signs that you have issues with your ventilation system.

Toilet Venting Steps

venting steps

To vent your toilet, you will make sure that you’re compliant with the applicable building codes. The steps will vary depending on your toilet’s design, the size of your pipes, and any local regulations.

1. Tie to the vent directly.

This is the most common setup. The drain pipe runs into the wall, then it drops vertically toward the sewer.

A vertical vent is installed upward from the vertical drop and into the roof. This allows gases to escape without issue.

Another option with this type of setup is to use a soil stack or vent stack. By directing the waste pipe inside, you can tie it using a wye fitting.

2. Connect under the toilet.

You can add your vent to the vertical portion of your waste pipe prior to the long-sweep elbow. Now, keep in mind that not all waste pipes are designed with long-sweep elbows, so this approach won’t work for everyone.

It’s best to do this using a reducing wye that has elbows positioned to change the vent’s direction however it’s needed.

3. Use a street elbow and wye to tie in.

Instead of using the vertical part of the pipe, you might also install a wye to the horizontal portion of the drain line. Then you glue a tilted street elbow to the outlet.

You vent this elbow vertically so it can control the direction of the waste.

Though this setup might sound complicated, it’s actually fairly simple to install. You’ll use a reducing wye to transition from a wider drain line to a two-inch vent.

4. Try a wet venting process instead.

You can try wet venting, too. This involves running your vent through another plumbing fixture.

Both the International Plumbing Code and Uniform Plumbing Code permit this space-saving, time-saving “hack.”

To do a wet vent job, you must use pipes that hold both water and air. You need a 2-inch venting pipe at the very least.

The most common point of connection is the sink drain. This drain connects to the toilet line using a reducing sanitary tee.

You might consider this installation option if you have a small bathroom.

Toilet Venting Options If You Don’t Have A Vent

cheater vent

Some houses don’t have a venting pipe, or they have a broken venting pipe that’s unusable. You can use “cheater vents” to do the job instead.

These pieces, called air admittance valves, aren’t legal for use everywhere. Always make sure you’re allowed to use them before you start.

Using An Air Admittance Valve To Vent Your Toilet

Air admittance valves let air enter your drainage system while keeping gases form the sewer from rising out of the drain. Instead of using a special pipe, it reacts to drainage system pressure and atmospheric pressure.

The seal closes due to gravitational pressure to keep air inside the piping. But when the drain pressure lowers, the seal opens up and allows fresh air inside.

Installing The Air Admittance Valve

You can install the valve under your sink. It can also be connected to the sewer system.

The exact installation process will vary depending on the valve. Typically, you’ll use an adaptor on a tee pipe in the sanitary connection.

Your model should come with instructions and diagrams.


What is the ideal distance for a toilet vent?

The UPC states that a toilet vent should only be 6 feet in distance.

Do any toilets self-vent?

Some toilets do self-vent. However, regulations stipulate that the trap arm needs to be vented one more time as an extra precaution.

Can an overflowing toilet be caused by a clogged vent?

Yes. In this case, problems with the pressure in the piping cause the water in the bowl to rise and overflow.

Can you use one vent for your shower, sink, and toilet?

You can use a wet venting system to connect multiple bathroom appliances together to save space.


Venting your toilet properly is incredibly important for your health and safety. It also allows you to flush with ease.

If your toilet is bubbling or has fluctuating water levels, those might be signs that there’s a problem with your venting system.