How to Vent a Toilet: Steps and Benefits

Have you ever handled your business in a toilet, and once you are done, you can’t stand the stench? Or even the moment you open that door, you are blown away by the pungent odor to a point you do your thing with one hand on your nose? It means that there is an issue with how the venting of that toilet was handled and you should vent it properly.

Vent a toilet by running the toilet drain pipe, connecting it to the waste pipe, connecting the ‘Y’ bend, then connecting the vent. Besides this method, you can vent your toilet using an Air Admittance Valve, sanitary crosses, and loop venting. Venting allows sewer gases escape and proper drainage.

A vent pipe plays a significant role in ensuring that the system is well saturated with air every time you flush the toilet to prevent clogging and unnecessary gases. It also helps in allowing the sewer gases to escape. Learning how to plumb a toilet drain is not a quick fix to bad toilet odor: a lot more goes into it.

How to Vent a Toilet

Does a Toilet Need a Vent?

Absolutely! Your toilet needs a vent for the following reasons:

1. Allow the Sewer Gases Escape

Two things happen when you flush your toilet. First, the forces of gravity and the water pressure allow the water and the waste to flow downwards. Secondly, the toilet sewer gases escape through the vent pipes.

A proper venting system will keep your toilet and entire home supplied with fresh air. As one of the push button toilet flush problems, poor venting can lead to awful odors indoors.

2. Protect the Trap Seals

This remains the primary reason behind toilet venting. A trap seal in a drainage system works rhythmically to allow water to pass through and close up once the water passes.

For a trap seal to work appropriately and seal tight, you need the vent to protect it.

Most toilet drainage systems function through siphonage and back pressure forces. The forces work against a trap seal, and that’s where a vent comes in. The vent can balance the air in the whole drainage system allowing the trap seals to function optimally.

3. Proper Drainage

The whole idea of a drainage system in your toilet is to allow the proper flow of wastewater. Imagine a scenario where the system fails to allow the water to flow. 

The bacteria from the sewer system will circulate, posing a health hazard. And there will be environmental pollution that comes with a foul odor spreading through the air.

To prevent all these, install a proper venting system that will supply air to the entire drainage system, thereby aiding the functionality of the sewer system.

4. Minimize Drainage Sound

You don’t want a drain system that attracts everyone’s attention every time it’s flushed. 

Allowing the trap seals to perform optimally and enough air within the entire system produces less noise when the toilet is flushed.

5. Reduces Clogging

Every drainage system requires enough water and air to be in a position to function correctly. For this reason, you will see some people introduce air and pressure to a clogged system to release the waste. A vent aids in preventing clogging by ensuring smooth water flow and enough air supply.

Knowing how to run plumbing for a toilet helps vent it properly and venting should be planned right from the plumbing stage for the best results. Clogs lead to lots of activities with the toilet which may lead to scratches and breakages. While you can easily repair a scratched toilet bowl, other repairs may not be so easy.

Other ways to reduce clogging is to keep unflushable items away from the toilet. For example, not all toilet seat covers can be flushed.

How to Vent a Toilet: Diagram

Diagrammatically, here’s how:

How to Vent a Toilet - Diagram

To vent a toilet, the steps are as follows:

1. Run the Toilet Drain Pipe

The toilet drainage system starts from the toilet flange you observe from the surface.

Connect the flange to a  toilet drain pipe 4”, reducing it by 3” on the elbow. The reduction helps allow the free flow of waste. A toilet drain pipe diagram shows the pipe running from the toilet’s base to the waste pipe.

2. Connect to the Waste Pipe

At the end, where you have reduced the elbow to 3”, fix a trap arm pipe that runs horizontally on the ground right from the flange. The trap can run under unrestricted plumbing codes areas for as long as you wish before connecting to the vent. The toilet P trap diagram above shows the shape of the trap which helps keep sewer gases away from the home through a column of water in it.

As in the toilet plumbing layout above, the waste pipe needs to have slope for the wastes to flow downwards and the gases upwards.

In areas under UPC requirements, the toilet vent distance should be 6 feet. Adhere to the trap-vent distancing requirements during installation to avoid remodeling once the authorities get to know. 

3. Connect the “Y” Bend

At the ideal distance, connect the “y” bend. The connector forms a Y shape, touching the ground trap to the vertical vent that runs upward above the roof.

Glue the connector at the right angle to ensure the vent and the trap function optimally without clogging the elbow.

At this point, if you wish, you can reduce the vertical end to 2” by connecting a reducer and leave the trap edge at 3”.

Again, if you live in areas under UPC restrictions, avoid reducing to 2”. Instead, let the Y connector remain at 3”.

4. Connect the Vent

At the vertical “Y” edge, connect the right side of the vent pipe and make it long enough to run through the roof.

The positioning of the connector is ideally at the edge, where the vent will run along a wall. Either on the exterior or, if internal, at the furthest corner.

Again, adhere to the UPC codes on vent size, but ideally, the pipe should not be less than 2”.

Ensure you get all the fittings right. But, first, consider the gravity and gradient of your ground.

The vent should protect the trap seals and retain good aeration on the entire drainage system with proper installation.

What to Consider Before Installing a Toilet Vent

As you plan on installing a toilet vent, you need to ponder the following first:

1. Vent Pipe Size

There are different sizes of vent pipes, and you need to consider the ideal size for your toilet.

Ideally, a vent pipe should not be less than a 2” PVC pipe. The essence of an extensive line is to ensure air flows freely in and out of the system. 2″ is also the bathroom vent pipe size and should be adhered to at all times. Any size smaller than that won’t vent properly.

2. Toilet drain size

It’s imperative to examine your toilet drain size. This will help you plan on the vent pipe size to acquire. 

The standard toilet drain size is 3” as it’s considered that the size can allow human waste to pass through freely. However, others are also above the 3” size. So the more extensive the drainpipe, the more waste can pass through without clogging.

For instance, a 4” drain size can carry waste double the size of a 3”. A big drain size requires a matching venting size.

3. Toilet Trap to Vent Distance (toilet trap arm length)

The recommended distance between the toilet trap to the vent is 6 feet. This means the vent feeds the trap within a 6ft distance.

How close they are to each other may affect the flow of the waste and the amount of air needed to prevent the sewer gases from backtracking.

You need to create enough distance between the two for the sake of momentum and flow.

4. Fixtures to Serve

How many utilities do you intend to serve with a single vent pipe? The more the facilities and the users of your toilets, the more vent pipes you will need.

5. Building Codes Requirements

There are local building codes and international codes that govern installing a toilet venting system. Avoid falling victim to non-compliance. Some are also more extensive hence the need to ensure you check your local building codes. They always have the requirements set out.

Under most UPC codes, the vent pipe shouldn’t be less than 1.5”.

Get the most updated version of the codes to avoid remodeling when you vent in err.

Other Toilet Venting Options

The option described above is the basic one. However, other options are described below that ensure the venting system functions optimally.

1. Air Admittance Valve (AAV)

This option involves installing an air valve to the system that opens up and closes at intervals to balance the pressure within the system.

The valve operates by suctioning air back to the sewer pipes by applying negative pressure or siphoning.

The air admittance valve for toilets works best when it’s hard to install the venting line. It also ensures a balance of the air pressure eliminating the air bubbles that may lead to gurgling or sending the sewer gases to your toilet.

2. Sanitary Crosses

A sanitary cross is a cross-like pipe connector with 4 open edges. The cross is connected to the drainage and venting system. Using the sanitary cross to feed the waste pipe allows a free flow of waste and air.

The essence of the cross is to allow enough air supply to the system to prevent the sewer gases from backtracking to your home.

Additionally, the cross allows for multiple piping balancing the negative and positive forces creating a balance on the pressure needed for the system to function.

3. Loop Venting

Although mostly preferred for other plumbing areas such as a sink system, a loop venting can still work on a toilet system. The only caveat is to check with the UPC  and local authorities on the legality of this venting on the toilet.

A loop venting uses the same ideology as the regular venting system, but this time, the vent doesn’t run vertically. Instead, it forms a loop allowing the system to suck air from a different direction.

This system involves a lot of plumbing work. If you aren’t a professional plumber, consider having other alternatives.

Can a Toilet, Shower, and Sink Share a Vent?

A toilet, sink and shower can share a vent when you have the right plumbing fittings on each system. The thumb rule is that other plumbing fixtures work with 1.5” fittings other than the toilet.

For the system to have balanced pressure that allows air to flow freely, make the drain pipe 3” and the vent 1.5”. This will prevent the sewer gases from these fixtures from getting back to your home.

If the toilets are sharing a drain and you’re wondering whether to go for a 3″ or 4″ drain for the toilet drain, choose the 4″ one since shared toilets will clog up ona 3-inch dain pipe.

Engage a professional plumber to handle the fixing to get it all right.

What is a Self Venting Toilet?

A self-venting system doesn’t have a venting pipe leaning on your wall and protruding through the roof. 

However, the exact mechanisms apply to the self-venting toilet which has a valve that opens and closes to balance the pressure in the system and allows for a smooth flow of waste.

The system works like a siphoning system that pulls the waste from the toilet bowl to the underground waste pipe.

The best thing about a self-venting toilet is that it works perfectly in preventing the sewer gases from filling up your home.

A self-venting system is ideal in areas with an already installed venting system. Additionally, the system allows you to avoid interfering with the roofing.

What is wet venting?

Wet venting has a single vent pipe acting as a waste pipe and serving multiple fixtures in your bathroom. A wet vent can serve your lavatory, shower, and bathtub. In addition, the system allows you to have a long wet vent as you would wish.

To perform optimally, a wet vent requires that the toilet be connected to the system’s extreme downside as it has the most sewer gases.

A 1.5” drain pipe acting as a wet vent can only handle two fixtures, while a 2” line can serve more than four fixtures. This implies a bigger diameter pipe say, 4”, works better as a wet vent.

Let every fixture release a 1-1.5” load size to avoid overwhelming the wet vent.

The plumbing codes also regulate the wet vent, and you need to familiarize yourself to do it right.

Before installing a wet vent system, check to ensure you have enough space to allow the wet vents to be positioned at the right angle. Also, check the existing plumbing system to ensure it will connect nicely.

Being a simplified plumbing system, you can direct the end to an air admittance valve. Only ensure the valve is the right size and can handle the high load of waste while at the same time maintaining a breath of fresh air in your bathroom.


Protect your home from the unwanted stench, gurgling and ensure a free flow of the wastewater through the entire system by having a properly installed venting system.

A sound venting system also keeps your loved ones healthy by ensuring the bacteria from the drainage system doesn’t escape the system. Additionally, the system is critical in reducing clogging instances in your drainage system.

With the various toilet venting options, you can settle for the one that works best for you. Consider all the relevant plumbing codes that apply to your locality to avoid running into problems with the authorities.

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