Can multiple plumbing fixtures share a vent?

Author: Chelsie Klocko V  |  Last update: Sunday, January 25, 2026

A horizontal wet vent could have as few as two fixtures or as many as ten fixtures but not more than two fixtures of any type can be connected to the system. Each wet vented fixture drain shall connect independently to the horizontal wet vent.

Does each plumbing fixture need its own vent?

Yes, every drain needs a separate vent to ensure the plumbing works properly and waste is removed.

How many fixtures can you put on one vent?

Under the Uniform Plumbing Code, a 2" vent can handle 24 fixture units(F.U). In a residence, a lavatory sink= 1.0 F.U., bathtub/shower= 2.0 F.U. and a toilet 1.6 gallon or less= 3.0 F.U, greater than 1.6 gallon= 4.0 F.U. So, 3-lav sinks, 3-1.6 toilets and 3-tubs/showers could be on one 2" vent.

Can a shower and toilet share a vent?

Yes, the toilet and sink can share the same vent, as can the shower. It's common to have one main vent pipe for multiple fixtures, although you might need a larger pipe. You should check with local building and plumbing codes to confirm you'll have adequate piping for your home.

What are the rules for plumbing venting?

In general, the vent should be as close as possible to the fixtures it serves. This proximity helps ensure the vent can effectively equalize air pressure and prevent sewer gas entry. However, there are some common guidelines to consider: The vent should be within 5 to 6 feet of the fixture drain it serves.

How Many Drains Can Be On One Vent?

How far can a plumbing vent be from a fixture?

For a 1 ½-inc pipe the vent should be 42 inches away at the most while a 2-inch pipe must have a maximum distance of 5 feet. For pipes that have a diameter of 3 inches the distance is 6 feet and for a 4-inch pipe the most it should be away from the vent is 10 feet.

Can I run a plumbing vent out the side of my house?

The good news is that your plumbing vent can indeed be run horizontally. When figuring out how to lay the pipes within your walls, it's more important to remember the clearance that is required by your spill line (the point where water overflows a tub, sink, or toilet).

Can two bathrooms share a vent pipe?

Well, you can't! You'd often blow air from one bathroom into the other, and local building inspectors wouldn't approve it. But while you can't have two fans with one vent, you can make one fan and one vent serve two bathrooms. This setup requires an in-line exhaust fan.

How many plumbing vents should a house have?

A general rule of thumb for a typical house with a typical plumbing layout is to have at least one vent for each drain pipe. Consider one full-size vent stack to be a coordinator for plumbing fittings, assuring smooth and efficient operation.

Does a plumbing vent have to go straight up?

Vent pipes must be installed so they stay dry. This means that they should emerge from the top of the drainpipe, either straight vertically or at no less than a 45-degree angle from horizontal, so that water cannot back up into them.

Can you have too many vents in your house?

It doesn't matter how few or how many vents your home has: if the AC can't do its job properly, your house won't be as cool, your electricity bill might be higher, and your AC unit will not be efficient. Keep rooms open to allow air to flow freely.

How many toilets can be on a 3 inch vent?

No more than four water closets or bathroom groups shall be installed within any branch interval of a 3" drain stack, and no more than a total of twelve on the stack.

Can multiple drains share a vent?

Common vent

This very simple concept allows two traps to be vented by the same vent. The two traps and their fixture drains can be either at the same level or at different levels, provided that they are on the same floor.

How many fixtures are on one vent?

An individual vent is permitted to vent two traps or trapped fixtures as a common vent. The traps or trapped fixtures being common vented shall be located on the same floor level.

Does every toilet in a house need a vent pipe?

The answer is, “Yes, absolutely.” Read on to learn the importance of the vent to your toilet and the rest of your plumbing system.

Does each plumbing fixture need a vent?

Every plumbing fixture needs to have a vent to work properly. Bath tubs, toilets, washing machines and kitchen sinks need the biggest plumbing vents.

What is stack venting?

The vent stack sits in the upper portion of your plumbing stack and ensures bad air is vented out of your home while taking in fresh air. It begins a little above your highest-level drain and rises upward through the roof. It is the only part in the stack that's never touched by drain water.

Does every room in a house need a vent?

While all rooms in your home need some form of ventilation to refresh the air, building regulations for new homes specify that mechanical ventilation is required in bathrooms, kitchens, and WCs.

Can a house have more than one plumbing vent?

No requirement to have more than one vent, as long as the pipe size is appropriate for the number of fixture units. What size is that pipe? Unless there is a local code amendment, vents need to run up through/above the roof. Again, unless there is a local code amendment, only one vent is needed to run through the roof.

Does each bathroom need a vent?

While building codes vary by location, most communities and states require an established form of bathroom ventilation. Exhaust fans are required in bathrooms that don't have a window or if the window is smaller than 3 square feet.

How far can a toilet be from a vent pipe?

According to the UPC, the distance between your trap and the vent should be no more than 6 feet. In other words, for the vent to work properly, it needs to feed into the drain line within 6 feet of the trapways that connect to it.

Do plumbing vents have to go through the roof?

They extend through the roof to allow sewer gases to escape from your home safely. Without proper venting, these gases can build up inside your home, leading to foul odors, health hazards, and even dangerous levels of methane gas.

Can you vent a bathroom out the side of the house?

Bathroom fan installation requires outside ventilation. If the bathroom exhaust fan or venting fan isn't accessible through an attic, you'll need to vent through a sidewall of your house.

Can you cover up a vent in your house?

You most likely thought covering your air vents would certainly save you energy, but it does the opposite. Considering that this could damage your cooling and heating system, fractures and other damage could allow air to leave your air ducts and cost you much more in energy bills.

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