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How To Install Vent Under Sink

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

Vent pipes are very important parts of plumbing systems. They allow air to flow freely through the system. If they are blocked or clogged, then water will get trapped inside and cause serious damage.

This can result in mold growth, rotting wood, and even structural problems.

Installing vents is a simple task that can save you from costly repairs later on.

In this article, we’ll show you step by step how to install a vent pipe, helping to ensure that your plumbing system stays in tip-top shape for longer.

How a Traditional Vent Line Works

A traditional vent line consists of a flexible tube that runs along with the ceiling above the sink. The vent pipe has an opening at one end that allows fresh air into the room when it’s open. 

When the faucet is turned off, the water drains down the drainpipe. As it does so, it pushes out any air bubbles and debris that may be present in the pipe.

These bubbles and debris collect in the bottom part of the sink and eventually make their way up the drainpipe.

The problem with this design is that there is no way for the water to escape if something goes wrong. If the pipe bursts or gets damaged, all the water will pour out and flood the area around the sink.

This could lead to serious injury or property damage.

The solution? A vent line. With a vent line installed, the water still flows down the drainpipe as usual. However, a small hole is drilled near the top of the pipe.

This hole connects directly to the outside atmosphere. It lets air enter the pipe when the sink is running, while also allowing potentially harmful gasses to escape.

This prevents water from flooding the area around the sink because any water that enters the pipe simply escapes out the top. 

Why You Need a Vent Pipe

Vent lines aren’t just useful for preventing water damage; they’re also necessary for proper ventilation.

Air needs to circulate throughout the house to keep rooms cool during the summer months and warm during the winter months.

Without adequate ventilation, indoor temperatures rise and fall too quickly, which causes drafts and other heating/cooling issues.

Vent pipes let fresh air into the home and prevent moisture from building up inside walls and ceilings. This helps to reduce the risk of mold and mildew buildup.

Another benefit of installing a vent pipe is that it keeps dust and dirt away from the kitchen sink.

Since these particles tend to accumulate in the bottom of the sink, having a vent pipe means that they won’t build up and create a mess.

What Is An Island Vent?

An island vent is a special type of vent designed for bathrooms. They look similar to standard vents, but they have extra features.

For example, they usually include a built-in aerator. This device creates tiny bubbles that keep the bathroom free of mold and mildew.

Why Do I Need One?

Islands can be helpful because they allow you to control the amount of moisture in your bathroom. They also let you conserve energy.

Aerators work by creating tiny bubbles that fill the room with oxygen. As the bubbles rise, they create positive pressure inside the room. This prevents mold and mildew from growing.

The air coming into your bathroom isn’t as fresh as the outside air. So, when you turn on the shower, the bathroom will get stuffy.

The best way to solve this problem is to install an island vent in your bathroom sink.

How Does An Island Vent Work?

When you turn on the faucet, the water pushes against the walls of the pipes. The force of the water pushes air out of the pipes. This makes the pipes smaller. It also reduces the amount of pressure inside them.

When you turn off the faucet, gravity pulls the water back down into the drain pipes. Because the pipes are now full of air, they expand. This allows the water to move easily through the pipes.

This process happens automatically every time you take a shower. But if you want to stop the expansion, you can install an island vent. These devices open and close automatically.

You don’t need to worry about adjusting the settings. All you have to do is plug it in.

How Can You Tell Which Type Of Vent Is Right For Your Bathroom?

As we have seen, there are two main types of vents available today: standard and island.

Standard vents are inexpensive and easy to install. They come in different sizes so you can choose one that fits your needs.

But standard vents aren’t very effective. They only help reduce humidity. And they don’t prevent mold and mildew from forming.

On the other hand, an island vent does all those things. Plus, it’s much easier to clean than a 

standard vent.

How an Air Admittance Valve (AAV) Works

An air admittance valve works similarly to a vent pipe. Instead of using a flexible tube, however, an AAV uses a rigid metal pipe.

This pipe usually comes in two pieces: the main section and a cap. The cap screws onto the main section and creates a tight seal between them.

When the faucet is running, the water pressure forces the cap upwards. This opens the connection between the two sections and allows air to pass through.

Once the faucet is shut off, the water pressure drops, causing the cap to drop back down. 

This closes the connection again and traps any remaining air bubbles and debris inside the pipe. An air admittance valve, therefore, is an important element of your plumbing, and a very effective method. 

The Pros Of Vents

If you want to know more about vents in sinks, read on below.

1. They Keep Your Kitchen From Flooding

When you have a leaky sink, you don’t just get wet; you also risk flooding the rest of your kitchen. That means you’ll have to clean up all sorts of messes, including dirty dishes, food waste, and even pet hair.

2. They Help Prevent Mold Growth

When you have a leaky drainpipe, you might notice mold growing inside your sink. If you let the problem go unchecked, you could soon see black spots appearing on your countertop.

3. They Improve Air Circulation

Ventilation helps prevent odors from building up in your home. When you have a vent installed under your sink, you can use it to help circulate fresh air throughout your kitchen.

4. They Reduce Noise Pollution

Noisy plumbing can cause problems with your sleep schedule. It’s important to make sure that you aren’t disturbed at night because noise pollution can lead to health issues like insomnia.

5. They Are Easy To Clean

You won’t have to worry about cleaning your sink after you turn off the water supply. All you’ll need to do is run some hot soapy water down the drain.

6. They Can Be Installed In Any Size Drainpipe

You don’t have to limit your options when it comes to installing a vent in your sink. There are many different types of vents available, including ones made specifically for drains.

7. They Save Space

A lot of people prefer to install their sinks next to their dishwashers or washing machines. However, if you have limited storage space, you might not be able to put them there.

8. They Make The Job Easier For Plumbers

Plumbing jobs can be difficult, especially if they involve working underneath your sink. By using a vent, you can save time and effort.

9. They’re Affordable

You don’t have much money to spend on your bathroom. But you still want to invest in something that makes your life easier. A vent is one way to achieve both goals.

The Cons Of Vents

There are a few downsides to installing a vent in a sink. Here are three things you should consider before making the decision:

1. They Might Not Work Well With Some Sinks

Some sinks come with built-in vents. These vents work well in most cases. However, if yours doesn’t include one, you might have trouble finding a replacement part. You could end up buying a whole new sink instead.

2. They May Damage Your Countertops

Installing a vent in your sink may damage your countertop. This happens when you remove the old pipe and replace it with a new one.

3. They Don’t Always Come With Installation Instructions

Installing a vent in your kitchen sink isn’t as simple as plugging it into an electrical outlet. You’ll need to follow specific instructions to ensure everything goes smoothly.

When to Install an AAV

Installing an AAV isn’t always necessary. In some cases, you can use a standard vent pipe instead. However, there are several reasons why you should consider adding an AAV to your system.

  • If Your House Is Older Than 50 Years Old

If your house was built before 1950, then it probably doesn’t have a vent pipe. That’s because most homes were constructed without a vent pipe. They weren’t required until after World War II. 

Before that time, houses didn’t need to be vented because they were typically made of wood.

Wood tends to dry out very slowly, so it wasn’t necessary to add vents to help speed up the drying process.

However, since many newer homes don’t have a vent pipe, they may suffer from problems like condensation or mold growth. These problems can cause serious health risks if not properly addressed.

  • If You Want to Prevent Mold Growth

Mold thrives on moist conditions. If you want to avoid this problem, then you’ll need to install an AAV. Otherwise, moisture will collect at the bottom of your sink and eventually lead to mold growth.

Mold spores are everywhere. Even though you might think that your kitchen sink is perfectly clean, there is still a risk of bacteria floating around.

When you wash dishes, food scraps get trapped under the rim of the sink. As long as those items remain wet, they provide a perfect breeding ground for mold.

The best way to prevent mold growth is by keeping your sink drain free of clogs. For example, make sure that all soap scum and grease get removed regularly. Also, try to keep your drains clear of hair and other foreign objects.

  • If You Live in a Hot Climate

In a hot climate, you’ll likely experience more frequent bathroom breaks than people who live in cooler climates. This makes it easy for moisture to build up in your home. If you’re experiencing excessive humidity, then you should consider installing an AAV.

  • If You Use a Shower Instead of a Tub

Many people choose to shower rather than take baths because they prefer the convenience.

Unfortunately, showers also create a lot of steam. The high levels of moisture can cause mold to grow quickly.

To prevent this problem, you should install an AAV. It will allow excess moisture to escape while trapping any small particles of dust and dirt.

  • If You Have a Low-Efficiency Fan

Low-efficiency fans tend to blow warm air throughout your entire home. Because of this, they often leave your home feeling stuffy.

An AAV helps solve this problem by allowing cool air to flow into your home. This creates a comfortable environment where you feel less stressed and more relaxed.

Why You Should Consider Adding an AAV to Your Home

There are plenty of benefits to having an AAV installed in your home. By choosing one over a traditional vent pipe, you can enjoy these advantages:

  • Improved Air Quality – An AAV allows fresh air to enter your home. This means that you won’t have to worry about breathing in harmful chemicals or allergens.
  • Increased Comfort – Having an AAV installed in the attic allows cool air to flow through your home. This keeps your home comfortable even when temperatures outside are extremely cold.
  • Preventing Mold Growth – Mold grows rapidly in damp environments. However, an AAV prevents moisture from building up inside your home. This eliminates the possibility of mold growing in the first place.
  • Preventing Mold Growth – Mold builds up in areas with lots of moisture. This includes bathrooms, basements, garages, crawl spaces, and kitchens. Installing an AAV will help prevent mold from forming in these areas.

What You’ll Need

To complete this project, you will need the following tools:

  • Circular Saw – When using a circular saw, always wear safety goggles when making cuts. Also, never operate the saw near an open flame.
  • Drill
  • Screws
  • Caulk Gun

Before You Begin

The task of adding an AAV to vent your sink is pretty straightforward, and the basic premise involves drilling holes in several locations.

Once you’ve completed this step, you’ll need to connect the pipes together using flexible tubing. Finally, you’ll need to seal the seams between each section of piping.

Step 1: Prepare Your Materials

You’ll want to use a drill to boreholes in the following places:

  • In the ceiling directly above the location where you plan on attaching the AAV.
  • At least two inches below the lowest point of the existing vent pipe.
  • At least three inches away from the wall.

Once you’ve made all of these holes, you’ll need to remove the old vent pipe. Next, you’ll need to attach the new AAV to the existing pipe.

Step 2: Remove the Old Pipe

Start by removing the old vent pipe. Start by turning off the water supply to the faucet.

Then, turn off the power switch at the main panel. After that, disconnect the electrical wires leading to the vent pipe. Finally, pull out the old vent pipe.

Step 3: Attach the New AAV

Next, you’ll need to prepare the area for the installation. First, make sure that there’s no debris or obstructions in the way.

If there are any items blocking the path, move them aside so that you can continue working without interruption.

Next, you’ll need to cut the hole in the ceiling. The best tool for cutting a hole in drywall is a circular saw.

Make sure that you wear protective eye gear while using it. Cutting holes in ceilings isn’t as dangerous as other types of construction work. 

However, if you’re not careful, you could damage the surrounding materials. Therefore, try to keep the blade pointed down during the process.

After cutting the hole, you’ll need to install a piece of plywood to cover the opening. Use screws to secure the board to the ceiling.

Now that you’ve prepared the area, you’ll be ready to begin installing the AAV.

How To Install An AAV

Once you have prepared the area, you will be ready to install your AAV.

First, you’ll need to insert a screwdriver into one end of the AAV. Then, rotate the device until the screw head comes out of the bottom of the unit.

Next, push the screwhead through the hole in the ceiling and into the wood covering. Repeat this step for every hole.

Next, you will need to feed the tube through the hole in the floor. Insert the tube into the hole and then twist it clockwise to tighten it against the wall. Repeat this step for each hole.

Finally, you’ll need to bend the ends of the tubes to form 90-degree angles. This will allow the pipes to fit snugly against the walls.

To finish the job, you’ll need to tape the joints between the sections of the pipe.

  • Seal the Seams Between Pipes

The last step is to seal the seams between the pipes. You’ll do this by wrapping duct tape around the joint.

To ensure that the tape sticks properly, apply some adhesive first. Then, wrap the tape over the seam.

Make sure that you leave enough space between the edges of the tape. Otherwise, you may find yourself with gaps when you remove the tape later on.

  • Turn On Water Supply

Turning on the water supply should be easy now. Just plug the sink back in and enjoy the convenience of having an extra sink!

Vent Types

When choosing a vent for your sink, you have several options. There are two types of vents:

PEX (polyethylene)

• PVC (plasticized vinyl)


Both polyethylene and plasticized vinyl are good choices for plumbing projects. Both types of vents are durable and easy to install.

However, there are differences between them. Polyethylene is more flexible than plasticized vinyl. This means that it can be cut easily. Plasticized vinyl has less flexibility. It’s harder to cut.

You should choose a type of vent based on how you plan to use your sink. For example, if you’re planning to wash dishes in it, you might want to go with polyethylene.

If you want to use it for cooking, you might want to get a plasticized vinyl vent.


Polyethylene is available in different sizes. Most people prefer to buy larger sizes because they last longer.

The size you select depends on how much water you expect to use in your sink.

The best way to determine which size you need is to measure the width and length of your sink.

Multiply those numbers together. Then add 5 inches to the total. This gives you the approximate diameter of the pipe needed to fit in your sink.

For example, if your sink measures 18 inches wide x 24 inches long, multiply those numbers together. Add 5 inches to the total number. That will give you the approximate diameter of your pipe.

For example, if your sink is 18 inches wide x 24 inches long, you’d multiply 18 x 24 to get 432. Add 5 inches to that number. You’ll end up with 437. That’s the approximate diameter of the PVC pipe you’ll need.

Plasticized Vinyl

Plasticized vinyl is usually sold as either 1/2″ or 3/4″. These sizes work well for most sinks. They’re easier to cut than polyethylene, but they’re still relatively easy to install.

To determine the appropriate size, follow these steps:

1. Measure the width and depth of your sink.

2. Multiply those measurements together.

3. Subtract 5 from the total.

This will tell you the approximate diameter of a pipe that will fit into your sink.

Once you’ve determined the correct size, you can order it online. You’ll find instructions on how to install it on the manufacturer’s website.

Once you’ve installed your new vent, test it. Turn off all faucets and flush the toilet.

Check to see whether any water leaks out of the vent. If so, you may need to replace the vent.

If you don’t hear anything when you turn on the tap, you probably didn’t need a cleanout after all. But if you do hear something, you should check to make sure no one was trapped inside the drain.

Do You Need an Air Gap and a Cleanout?

Before you decide whether or not you need an air gap and a cleanout, you should know what these terms mean. An air gap is a small opening between two pipes.

It allows air to flow through the pipes while preventing liquids from leaking out. A cleanout is a hole that connects to a sewer line. It lets waste materials leave the house without causing any leaks.

Air Gaps vs. Cleanouts

If you live in a dry climate where humidity levels are low, you probably don’t need an air gap.

If you live in a humid area, however, you might need one. Water tends to collect inside pipes during heavy rainstorms. This causes pressure to build up inside the pipes. 

If this pressure builds up too high, it could burst open. That would result in a flood that could destroy your home.

An air gap helps prevent this problem by allowing air to flow freely through the pipes.

Cleanouts also help prevent flooding. When water enters a drain, it often flows down the pipe.

Eventually, it reaches a sewer line. At this point, it’s no longer dirty. Instead, it’s treated like regular sewage. This means that it leaves the house safely.

Cleanouts aren’t always necessary. In some areas, homeowners use a vent to release excess moisture.

If you did need a cleanout, here’s what you should do:

1. Remove the old vent by unscrewing it.

2. Clean out the area around the vent using a brush and soap.

3. Replace the vent.

4. Test the vent again.

5. Flush the toilet and run cold water through the sink until the problem goes away.

6. Turn off the water supply to the sink.

7. Drain the sink completely.

8. Run hot water through the sink until it stops dripping.

9. Fill the sink back up with warm water.

10. Turn on the water supply to the kitchen sink.

11. Use a sponge or rag to wipe down the sink.

12. Repeat Steps 9-10 until the leak has stopped.

13. Let the sink dry overnight.

14. Reinstall the drain cover.

15. Turn on the water to the sink.

16. Run cold water through the sink to flush out the pipes.

17. Wait at least 30 minutes before running hot water through the sink.

18. Test the sink to make sure there are no more leaks.

19. If everything works fine, you’re done!

Final Thoughts

Plumbing vents can be a relatively simple way to improve the performance and condition of your plumbing system, and this small change can make a significant difference. 

With a little research to choose the best vent for you and some understanding of basic plumbing fixtures, you can help your system run smoothly – and remember if in doubt, there is always an option to contact a licensed plumber who will help to transform your plumbing system for the better!

author avatar
Charlie Hardcastle


On Key

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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