What Is A Wet Vent In Plumbing?

Last Updated On July 14, 2024

Updated on July 23, 2022



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What Is A Wet Vent In Plumbing

What is a wet plumbing vent? A wet vent is a plumbing term used to describe a type of ventilation system. This system allows air to flow through the vent pipes even when water is flowing in them. 

This helps to prevent clogs and ensure proper airflow in your plumbing system. In this blog post, we will explain how wet vents work and when you should use them. We will also provide tips on how to install a wet vent in your own plumbing system!

In this PlumbingNav guide, we will cover:

  • What is a wet vent in plumbing and how does it work?
  • Wet vent vs. dry vent
  • Hot to install wet vent ventilation

What's In This Guide?

      What Is A Wet Vent In Plumbing and How Does It Work?

      A wet vent is a type of ventilation system that allows air to flow through the pipes even when water is flowing in them thanks to the clever design involving both horizontal and vertical pipes. 

      A wet vent may act as a waste pipe for one fixture while simultaneously acting as a vent pipe for other fixtures. For example, the pipe can act as a fixture drain for a bathroom sink and a fixture vent for the toilet at the same time. 

      The vent pipe will lead the wastewater out through the sink drain line without interrupting the ventilation activity regulating the toilet.

      Common Uses For A Wet Vent In Your Home Plumbing System

      Wet venting works best with closeby drains. 

      You will often come across a wet vent setup to drain both a toilet and a bathroom sink or a laundry machine and a utility sink. 

      Wet Vent Vs. Dry Vent

      Dry vent systems are more reliable as they connect each fixture to your home’s vertical vent stack with a dedicated vent pipe. The pipes send the air outside through the roof. However, a dry vent cannot transport water. 

      Since wet vents can’t easily access the main vent, they send air out of your pipes through a special pipe, which can travel either horizontally or vertically. Wet vents are more delicate than a simple dry vent system.

      It must stay at the perfect angle, and there’s more room for error since it supports multiple fixtures at once. However, a wet vent system provides more flexibility, making it preferable, if not the only option, for remote areas of your home.

      did you know what is a wet plumbing vent

      Benefits of a Wet Vent System

      There are several benefits of using a wet vent plumbing system:

      • Prevent clogs

      A wet vent system can use its airflow to help move debris accumulating in the drain pipe, stopping it before it creates a blockage. It can also make things easier when you do need to clear a clog in your bathroom sink.

      • Provide adequate air flow to remote pipes

      You need to vent your plumbing pipe, and provide air gaps in plumbing where required. A wet vent system gets the job done in areas you couldn’t access easily using a dry vent system. Without proper ventilation, sewer gas may manage to find its way back into the house. You may also get a gurgling sound coming from your bathroom sink, indicating negative pressure.

      Homeowners can choose to use an air admittance valve (AAV) in some situations, but it won’t work as well as a wet vent.

      • Vent multiple fixtures at once, which can save you time and money

      All plumbing fixtures require ventilation. Venting each bathroom fixture individually will cost more in both materials and labor since it takes more piping and more time compared to connecting multiple fixtures to one vent pipe.

      See this related post for how to get air ​​out of water lines.

      How To Install Wet Vent Ventilation

      Before you take on your plumbing ventilation as a DIY task, carefully go over the residential building regulations in your area. Many states require a licensed plumber to perform plumbing ventilation work. 

      If your location will let you do it yourself, you still may need to get a permit to complete the work as an unlicensed homeowner. 

      Common building codes regarding wet vents generally accepted throughout the United States and Canada (keep in mind that some locations may have stricter regulations) include:

      • All fixtures must occupy the same floor of the house
      • Your toilet MUST be lower than the other units attached to the wet vent system
      • The vent pipe must enter the horizontal drain line at a 45-degree angle or lower
      • The horizontal wet vent pipe must have clips to support it every 4 ft. 

      Attach the vent pipe to the different fixtures using various adapters. Ensure that you have the correct adapters and that the fixtures meet local standards regarding distance and compatibility. 

      You may need access to the wall to complete the installation. You’ll also need to cut pipe to the exact size you need using a hacksaw or alternative cutting tool. 

      Watch this video to learn more about different venting setups:

      Related Content: What is a plumbing riser?

      Wet Vent Sizing

      Use the following table to learn the required vent pipe size based on the drainage fixture unit (dfu) load according to the International Plumbing Code:

      Vent Pipe Size (diameter in inches)Drainage fixture unit (dfu) load

      Frequently Asked Questions Regarding Wet Vents in Plumbing

      What is the difference between a wet vent and a dry vent?

      A wet vent drains one elevated plumbing fixture and ventilates a lower fixture at the same time using horizontal and vertical pipes, also called a loop vent in plumbing. Wet plumbing vents include strict regulations and only work when both fixtures are close to each other.

      A dry vent ventilates each fixture separately. Dry vent requires more vent piping since it can’t use the same pipe for multiple fixtures like with a wet vent. Such as venting a kitchen sink.

      How can you tell if you have a wet vent or dry vent installed in your home?

      To determine if your home uses a wet vent system, look behind the fixtures in question to visibly check for a pipe connecting the nearby items. You should be able to see whether a pipe connects the items or not. 

      Can a toilet use a wet vent?

      A toilet can use a wet vent. However, gravity flush toilets must be located lower than any other fixture connected to the ventilation setup. If not installed properly, you may experience unsanitary conditions as wet vent systems are not made to carry solid waste. This is a consideration in tankless toilets.

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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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