How To Make A Plumbing Loop Vent: A Step-By-Step Guide

Last Updated On June 11, 2024

Updated on April 25, 2023



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how to make a plumbing loop vent

Do you have plumbing ventilation issues? If you’re looking for an easy way to improve the ventilation in your plumbing system, a loop vent (also known as a circuit vent) might be the answer. 

Loop vents are a type of plumbing ventilation system that have several advantages (and some disadvantages) over other types of vents. 

In this PlumbingNav guide, we will cover:

  • What is a plumbing loop vent?
  • Advantages and disadvantages of a loop vent
  • How to install a plumbing loop vent
  • Tips on maintaining your loop vent

What's In This Guide?

      What Is A Plumbing Loop Vent?

      Loop vents are a type of plumbing vent piping system that is installed in the main drain line. 

      The loop vent consists of a horizontal section of pipe that is installed between the two vertical drain lines. This type of vent is usually installed at the highest point in the drainage system and circulates air with a vent pipe underneath the floor that then connects to your main vent.

      The loop vent allows air to enter the drainage system and provides a way for the air to escape, making it especially useful for an island vent or when venting a remote bathroom. 

      You can incorporate a loop vent into a wet vent plumbing system that connects two nearby fixtures to act as both a drain pipe and a vent pipe instead of providing an individual vent for each fixture. 

      All plumbing fixtures require a vent connection according to the uniform plumbing code. The ventilation regulates air pressure, preventing negative pressure in your plumbing system. If you don’t ventilate properly, you may experience gurgling in your pipes or improper function. It also prevents potential backflow issues.

      How to Install a Plumbing Loop Vent

      While many areas have restrictions that prohibit homeowners from installing their own residential plumbing ventilation without a proper license and permit, it can be helpful to understand the process.

      Here are four simple steps to help you understand how to install a loop vent:

      Step One: Identify the highest point in your drainage pipe. 

      This is where you’ll install the loop vent. Keep in mind that the loop vent must be at least 4” higher than the top of the waste pipe.

      Step Two: Cut a hole in the pipe at the highest point. 

      Step Three: Attach the loop vent to the pipe and seal it with silicone caulk or another type of sealant.

      Step Four: Connect the other end of the loop vent to an air release valve

      See the following video for more details on how to install a plumbing loop vent:

      Tips For Maintaining Your Plumbing Loop Vent System

      There are several things that you can do to maintain your main loop vent and keep it functioning properly. 

      Make sure that the drain itself is not blocked by debris or other objects with regular drain cleaning. 

      If you opted for a mechanical vent as seen in the above video, ensure it’s in working order at least every 2 years or so. There are often no failure indicators, so you’ll need to do this manually.

      For nearby garbage disposal installations, ensure drain tie-ins remain in proper working order and are free of clogs to prevent backflow issues. See this post when connecting it to a dishwasher.

      By following these simple tips, you can help to keep your plumbing system running smoothly and prevent costly repairs.

      Did You Know? You can expect to pay anywhere from $80 – $240 for new plumbing vent installation if your current pipes become irreparably damaged. 

      did you know how to make a plumbing loop vent

      Loop Vent Pipes

      You can use the following materials for your loop vent, depending on the other pipe materials you’re working with and your preferences:

      To pick the correct piping material, consider what conditions the pipe will endure. For example, some piping material withstands hot water better, if ventilating pipes that are connected to your water heater.

      The size of the pipe depends on the size of the trap and its slope. See the following sizing guidelines for your circuit ventilation system according to the plumbing code:

      Size of trapslopeDistance from trap

      The Advantages Of A Plumbing Loop Vent 

      One advantage of using loop vents is that they are less likely to become blocked than other types of vents since the air contributes to proper water flow.

      Another advantage is that they provide a way for air to enter the drainage system without having to go through the roof. 

      The Disadvantages of a Plumbing Loop Vent

      Loop vents also have some disadvantages. One disadvantage is that they can be difficult to install if you don’t have experience with plumbing ventilation systems since you need access to a floor drain. Sometimes air gaps are created and only discovered once walls are sealed up. 

      Furthermore, horizontal vent pipes must be installed at the perfect angle and slope to work properly. This requires additional expertise when working on top floors where plumbing risers might be present.

      Another disadvantage is that they can be loud when the air is released.

      Alternatives to a Loop Air Vent

      Most people use a loop vent because of the flexibility it offers. However, you should know that you can use an air admittance valve (AAV) instead of a loop vent. 

      While easier to install than a loop vent, an AAV comes with very specific installation regulations, too. And the loop vent will provide better results. 

      Running into issues venting your kitchen? Learn how to vent under a kitchen window.

      FAQ’s About Plumbing Loop Vents

      Why do you need a loop vent?

      A loop vent gives you the ability to vent and drain an isolated plumbing fixture, such as a kitchen island or remote bathroom sink.

      How high does a loop vent need to be?

      You want the loop vent to be at least 4” higher than the top of your drain. 

      Can a plumbing vent have an elbow?

      A vent elbow, a 90-degree vent adapter, can’t be used when underwater. If used, it can get water into the vent pipe.

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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