Can A Toilet, Shower, And Sink Share A Vent?

Do you ever wonder if your bathroom sink, toilet, or shower can share a vent? You have come to the right place. We have researched this topic to provide updated information to you.

A vent shared by a sink, toilet, and shower is possible and practical. However, there are requirements before they share a vent together:

  • Effective drainage system
  • Vent specifications on parts or fixtures
  • Venting system
  • Distance between units

This article explains the requirements for sharing your bathroom sink, toilet, and shower (or bathtub) vent. We also tackled the importance of a plumbing vent, the difference between a drain and vent pipes, and what parts to buy for your bathroom vent process, so keep reading.

Requirements For A Bathroom Vent Process

There are requirements to make sharing a vent in your bathroom fixtures work properly. Otherwise, it may not properly prevent drain clogs, and you may need to contact a professional drain cleaning company.

Effective Drainage System

A drainage system works if it removes any excess water from the house and helps prevent water-related damage to your home. Aside from health considerations, proper drainage must follow the building code in your area.

An effective drainage system does the following two things: 

  1. Drainage must allow air into the system. This prevents slow drains or a vacuum-like action. 
  1. Drainage must allow sewer gases to vent outdoors. Sewer gases may flow into the building drain pipes from the sewer or septic system. The plumbing vent system must carry these gases outside, above the building roof. This prevents foul or dangerous odors from getting inside the house.

Vent Specifications on Parts or Fixtures

The plumbing pipes need specific sizes for vent sharing. Specifications below are the best practices:

  • The toilet drain should be 3 inches
  • The sink drain should be 1.5 inches
  • The shared sink drain and toilet vent should be 2 inches
  • The vent going up should be 1.5 inches
  • The 2-inch drain connects to the 3-inch toilet drain using a "Y" instead of a "T"

The bathroom toilet and sink are wet-vented and connect to the vertical leg of the toilet drain. The shower connects to the wet vent, with its pipe off the drain. If the shower's distance is less than 5 feet from the vent, there is no need for an extra vent.

It's a practical way to save time, effort, and money on materials.

You also need:

  • PVC pipe and fittings
  • PVC primer and cement
  • Pipe strap
  • Fitting to join to the existing drainpipe
  • Basic tools

Venting System

The venting process of your bathroom prevents wastewater and sewage from contaminating your water supply. 

Wet venting is a practical solution for toilets and sinks. The drain for the sink serves as the vent for the toilet. A wet vent system drains the water from one fixture while venting the air from the other unit. A dry vent transports air without carrying out water by the system. 

Wet vents may vent one fixture and drain another, whereas dry vents usually vent air from one unit at a time.

Distances between Units

The toilet, sink, and shower must be near each other. Otherwise, vent sharing is not possible.

Modern grey designer bathroom with herringbone shower tiling

What is the Drain-Waste-Vent (DWV) System?

The DWV system is also known as your home's sanitary system. It consists of all the plumbing minus the parts used for the water supply.

The DWV system includes all the drainpipes, drains, and vents. Usually, when wastewater enters the system, it has to pass through a drain trap (shaped as U or P), which creates a seal to prevent sewer gases from getting in your home.

 The drain pipes allow wastewater to pass through to the main sewer line. This sewer line is underground and sends sewage to the city or municipal sewer system or your septic tank if installed.

What is AAV (Air Admittance Valve)?

AAVs are a fixture that allows air to enter a plumbing drainage system. It occurs when negative pressure develops in the pipes due to water flow. When the pressure in the piping system equalizes (no water flow), gravity closes the vent and prevents sewer gases from entering the house.

What is the difference between a drain pipe and a vent pipe?

Drainage and vent pipes work together to remove water and waste efficiently.

Drainage pipes carry wastewater out of the house into the city sewer or your septic tank if you have one.

Vent pipes provide fresh air to plumbing fixtures in your home. It helps the plumbing system move water using the drainage pipes whenever someone flushes the toilet or drains the sink.

What are the purposes of plumbing vents?

under sink plumbing and drainage system, water purification system install under modern kitchen sink, shallow depth of field

Protecting trap seals is the primary purpose of a plumbing vent. A trap seal is a design where water seals a pipe and aid in its movement throughout the plumbing pipe inside the house. The most commonly used trap is called the U-trap found under the sink. The second most common is called the P-trap.  

These fixtures hold water inside a bent pipe and create a seal between the fixture's drain and the pipe system. The seal keeps gasses inside the house and creates a siphoning effect once water flows down the drain.

 Other purposes are as follows:

  • Better drain flow—plumbing vent allows air to get inside and push the water out drainage pipes. There are problems with drain flow if the plumbing vent is clogged.
  • Transport sewer gas outside—plumbing vent keeps the house safe from poisonous and smelly odors by transporting these gases outside.
  • To vent the sewer—helps transport waste materials outside the home.

What Does A Plumbing Vent System Consist Of?

male hands twist the drain pipe under the sink in the kitchen.

It consists of a pipe (or pipes) that provide a flow of air to or from a drainage system. It also provides a circulation of air within such a system to protect trap seals from siphonage and backpressure.

What is the connection of a trap seal with plumbing vents?

 A trap seal works with plumbing vents and creates two positive effects: 

  • It prevents bad smells from moving out of the pipes and into the house.
  • It makes water drain faster and moves waste materials trapped in the water, making it less likely to get stuck in the pipes.

What are DFUs (drain fixture units)?

A Fixture Unit (FU) or Drain Fixture Unit (DFU) is a measuring unit based on the rate of discharge, operation timing, and frequency of use of a fixture that expresses the hydraulic load imposed by that fixture on the sanitary plumbing.

DFUs calculate the drainage flow from fixtures and the required capacities of sewer service systems.

What are the parts you need to install a bathroom vent process?

Installation of a grease trap, What are the parts you need to install a bathroom vent process?

You'll need the following parts in your bathroom venting process:

Air admittance valve trap

This assembly prevents sewer gas and odors from escaping into the house. It is used for kitchen and bathroom sink vents. 

Click here to see the AAV trap assembly kit on Amazon.

Tubular trap assembly

This fixture is used for a 1.5-inch vent individual, branch, and stack vents, and can be added to vents in pump waste and sewer ejector systems. It terminates the vent pipe with 2 times the superior sealing capacity.

Click here to see this 1.5-inch Tuuber vent valve on Amazon.

Larger tubular trap assembly

This is another model similar to the 1.5-inch Tuuber vent valve with a larger vent size. 

Click here to see this 2 inches Tuuber vent valve at Amazon

PVC air admittance valve 

This valve with PVC adapter is ideal for a single fixture or group, with a capacity of 160 DFUs (drain fixture units) on a branch and 24 DFUs on a stack. It creates ventilation that prevents water loss in seals in traps. It uses gravity to auto-seal and fends off the circulation of smelly odors in the bathroom or odors from the drainage.

Click here to see this AAV with PVC adapter at Amazon

In Closing

Small bathroom inside a room with ambient lightnings and bathtub.

A bathroom sink, toilet, and shower (or a bathtub) can share a vent. It's a practical solution that professionals prefer. For your bathroom vent process to function, your home must have a drainage system, the right fixtures adhering to your local building code, a venting system like wet venting, and bathroom units located near each other for the vent sharing to work.

If you like this article, we recommend these related posts:

Is A Shower Base Better Than Tiles?

Can You Add A Toilet To A Laundry Room? [Yes, But Here’s What You Need To Know!]

Does A Double Sink Vanity Share The Same Drain?

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