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How to Vent a Toilet without a Vent?

We use our toilets for flushing and disposing of our liquid and solid waste, but none of us like that awful smell. Unfortunately, it is a regular part of the action happening in toilets, which makes proper venting an essential part of our homes.

Nowadays, it is not enough to pay extra attention to excellent venting systems. You need to follow modern innovations in getting rid of awful odors. Therefore, it is a good idea to understand the venting system and why do we need it. Let’s see.

What is Venting?

What is Venting

Even though people usually believe that venting the American standard toilet is just quick ventilation regarding bad smells, it is not that simple. The process is more complicated and in direct connection with plumbing and sewer pipes.

As you know, atmospheric pressure affects everything on the planet, including our toilets. That pressure needs to be in balance in waste pipes to allow the correct work of water supply and sewerage systems.

If you have a closed sewage system, you will have a lot of problems with misbalanced pressure. Since it shouldn’t be too low or too high, you need to find a way to allow the equalizing of the pressure in the pipes with atmospheric one.

Actually, it is not too hard to achieve that. You need to implement one vertical vent pipe to the top of your roof, and it will vent the entire system. That open pipe, connected to the waste, sewer, and pipes, will supply air to the waste pipes.

When you flush the water in your toilet, the odor will go smoothly through the vent pipe, thanks to the process of equalizing the atmospheric pressure in the drain system. As a result, there will be neither bad smell nor strange noises coming out of sewer pipes.

Moreover, you will not have problems with clogged drains and slow drainage of wastewater. Therefore, venting the pipes is necessary and obligated by building laws. Most houses have these pipes in the roof, far from windows and household ventilation.

Since these pipes penetrate your roof, you will need to mend leaky roofs and ruined ceilings sooner or later. Luckily, there are a few more elegant solutions.

How to Vent without a Vent

How to Vent without a Vent


Don’t worry if you do not have a vent pipe in your house, or if it is blocked and you can’t fix it. Instead of thinking about massive construction projects, you can use an Air Admittance Valve, well-known as a cheater vent.

You may have heard that they are illegal and unreliable, but you shouldn’t believe every rumor. In many situations, it is impossible to install standard venting for various reasons, and the installation of Air Admittance Valves can solve that problem. It is a simple mechanism that replaces classical venting pipe systems. Atmospheric pressure goes through the valve and has the same effect as in the classical venting.

Actually, this system is not a rare solution in Europe and many other parts of the world. In the US, the legal issue of Air Admittance Valve is a bit of a grey area. Several famous manufacturers make these systems on the American soil, and the majority of local hardware and plumbing shops sell them.

The plumbers install Air Admittance Valves regularly, and there are no legal actions against installing them so far. If you are not sure what to do, you can always check with local plumbing authorities and associations. They will tell you if it is legal to install this system in the region where you live.

How Does Air Admittance Valves Work?

Air Admittance Valve (AAV) allows the air to enter the drain system and prevents bad smells from coming out at the same time. It is possible because these valves react to pressure in the drainage system.

If the lower atmospheric pressure appears in the drainage system, the seal in the valve will automatically open and lift. As a result, the fresh air will come in and help to equalize the pressure.

After equalizing it, the sealing is automatically closed thanks to the gravity pulling it back to its position. When the seal in the valve closes, it prevents bad odors from escaping the sewer system. It will stay closed as long as the pressure in the drainage pipes is positive.

How Does Air Admittance Valves Look?

air admittance valve

Air Admittance Valves come in different sizes, materials, and colors. They are simple assembly valves with a small mechanism on the top, and their design depends on capacity and the manufacturer.

Most manufacturers use modern plastic materials to make high-quality valves. Some of them can have a screen preventing insects from crawling in and out of a sewer. Therefore, nothing can come in or out of the vent except the air.

Depending on the capacity of the drainage, you will need valves of different sizes. Also, it is not the same if you are using it for one household or more of them. You can quickly calculate which size of valves you need to use in your home. Determine how much waste fluid your system releases per second and the pressure value necessary for the realization of waste.

Some standard measures are from 119 US GPM (7.5 l/s) at -250 Pa for mini valves to 507 US GPM (32 l/s) at -250 Pa for maxi valves. Keep in mind that 10 Pa is equivalent to 0.04 inches (1 mm) water gauge.

Most valves will work at extreme temperatures from -4 F (-20 C) to 140 F (60 C), but it directly depends on the model you choose.

In the end, you should install one or more Air Admitting Valve according to your needs. That means that you should determine if your valves need to support the drain ventilation for one plumbing fixture or a few of them.

How to Install Air Admittance Valves

When you decide to install Air Admittance Valve, you will need to provide a tee sanitary connection pipe with adaptor fittings first. Only that way you can install this system. No matter which brand you have chosen, the installation is easy and quite similar. Plus, most manufacturers include the instructions to the set, as well.

Pay special attention to the sanitary tee pipe. It is of great importance because you need to install the vent there. Place it up-righted, but you don’t need to worry if it is not possible in your case. You can adjust it for 15 degrees of vertical alignment.

Then connect the left and right parts of the tee pipe with the existing sewer pipe. Position the disconnected piece of the pipe to the ceiling.

Before connecting the fittings of the pipe to the vent, you should connect the vent with Teflon tape. Keep in mind that all vents have tread, which you need to connect to the tee pipe.

Where to Install the Air Admittance Valve?

Where to Install the Air Admittance Valve

Basically, you can install Air Admittance Valve anywhere, which makes it practical and highly convenient.

If you have an apartment, you can install this system under your kitchen or bathroom sink because it doesn’t require a lot of space. You need to harmonize dimensions of the area with the sizes of the valves and tee sanitarian waste pipe. It is enough to determine the capacity of the valves and how many units you need.

If you have a house, you can install the system anywhere, including the attic above the isolation or the basement connected to a sewer system. If you have a wall cavity, you can install the Air Admittance Valve there. In that case, you should purchase the model with a recess box and a grill, so that the air can come in and out.

Since you want to install it to vent the toilet, the best solution is to attach the system to the toilet drain. Keep in mind that you need to install Air Admittance Valve at least 4 inches (10 cm) higher than a drain line.

To finish the job successfully, you will need a tee sanitarian pipe. All additional installations will depend on the plumbing in your household. According to your needs, you should purchase the necessary extra parts, fittings, PVC glues, and Teflon tape.

Is the Air Admittance Valve Reliable?

Many people have a lot of concerns and doubts about Air Admittance Valve. On the other hand, many experts agree that this system is the right solution for venting the toilet without a vent.

The primary question is whether waste from sewer may come out of the AAV in case of clogging inside the drain pipes. You should know that it is practically not possible. After numerous testing for leaking and over-flooding, there is clear proof that it will not happen regardless of the circumstances.

Be sure that Air Admittance Valve is a high-quality, safe, and sound solution, which will work without a mess or leaking. No matter if you test it in dual flush toilets, bathtubs drain, or gravity-fed flushing toilets, this modern plumbing gadget will work impeccably.


Even though Air Admittance Valve sounds too good to be true, it works thanks to the fundamental physics laws and advanced technology.

Nowadays, many domestic and foreign manufacturers make this system. These systems are different in design, capacity, materials, and temperatures they can function at. You should choose the brand you trust the most and the model with the longest guarantee.

8 thoughts on “How to Vent a Toilet without a Vent?”

  1. BS. There are CODES. You might want to refer people to the current plumbing code instead of saying that AAV’s can be installed anywhere.
    This is why I see so many violations of code in houses.

  2. Irrespective of the ‘codes’ air admittance valves work and provide a healthy solution. Emma is suggesting – rightly – that in the US – the codes have not caught up with the technology and its successful application. So they should be ‘violated’!

    • Irrespective of the codes, the vents have to be placed to function properly based on physics and assure that sewer gases remain in the sewer or are released safely into the atmosphere. Therefore NO they can not just be placed anywhere and the CODES for VENTING must be followed in their placement. This is about PHYSICS and proper FUNCTION.

  3. If I have a toilet that is vented through the roof, and I have rodded out the sewer line, and it still is gurgling, if I added a cheater valve under the sink, could that help solve my problem? Could it cause any additional problems? Thank you, Stephen

  4. How much is air admittance valve? How to get 1?

    • Home Depot or Lowes are your best bet price range is from $10-$30 depending on style & size

  5. Thank you for sharing most valuable information about Vent A Toilet Without Roof Vent.
    As I undersootd , We can install Air Admittance Valve anywhere, which makes it practical and highly convenient. But my question is that, for public toilet block where there are vertical plumbing duct altrough form one floor to another floor and rvented through the roof is impossible. In this context AAV is possible to installed into that closed duct or will it be workable? Or any other alternative solution, please guide me.

    • First, they can NOT just be installed anywhere. Even if your local codes do not allow or address AAV’s all vents of any kind must be installed in accordance with codes to function properly (in this case the codes are designed to follow physics.
      If you live in a multi-story building, then the building normally uses a waste stack or soil stack. These are engineered with required venting at every floor. If your system is gurgling or not flushing/draining then something is wrong with the system.
      The owner or landlord must use licensed professionals to make any necessary repairs and the system should work properly. Basically a vent is probably blocked.
      Contact your HEALTH department or CODE ENFORCEMENT department to make the landlord repair it.


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