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Can Plumbing Vents Run Horizontally?

By 15 May 2024Resources

Can Plumbing Vents Run Horizontally?

Just because your plumbing is hidden behind a wall doesn’t mean you shouldn’t pay attention to how your pipes are structured. Plumbing vents are one of the most important components of your system, but they might not have room to run vertically. Can you run a plumbing vent horizontally according to the building codes? 

If you find yourself asking this question, here is what you need to know about the positioning of your vents: 

What Do Plumbing Vents Do? 

Before we dive into whether plumbing vents can be run horizontally, it’s important to know what function a vent plays in your overall plumbing system. Vent pipes exist to eliminate air from your plumbing, decreasing the odds of having a gurgling and noisy drain. 

To keep home plumbing running smoothly, you need to have plumbing vents. 

Another important point about plumbing vent systems is that no vacuum is created in the pipes. If there were to be a vacuum, you’d run the risk of having sewer gases and material back up in the pipes and enter your home. Nobody wants that; it’s dangerous—so it’s important to have vent lines installed on the proper slope. 

The question is: Can you run vent pipes horizontally?

Can Plumbing Vents Run Horizontally?

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). 

As long as you connect vent lines about 16.2 cm / 6 inches above the spill line, they can run in any direction. The key here is to make sure that your vent system doesn’t have any risk of traps. A trap is when you have a point in your drain line where water can no longer be pushed out of the pipe. 

In other words, it should be able to run freely through your pipes all the way to the sewer. This means you may need to think more closely about the slope of your vent lines. 

How Long Can Horizontal Vents Run? 

While you can indeed run a horizontal vent pipe, you can’t do it indefinitely; this is designed to provide your pipes with the ability to drain into the sewer system. The typical rule of thumb according to code requires you to run a horizontal pipe for no more than one-third of the total length. 

However, there are exceptions to this building code: If your minimum pipe size is increased by one pipe size, there are no maximum length limitations implied in the system. 

Be sure to brush up on your building codes before you start structuring your plumbing system. It might be a better idea to size up your pipes and run longer stretches of vent pipe horizontally as opposed to being limited to the one-third rule. 

Spacing for Vents and Traps

Your local plumbing inspector is going to be looking at the entire vent system. Whether it’s a vertical pipe or a horizontal one, the important thing is to ensure that your vents and traps are appropriately placed. Every trap requires a vent (except for toilets), so knowing this aspect of your plumbing system in great detail is required. 

The distance between a trap and a vent depends on the size of the plumbing pipe. Your horizontal vent might need to be 76.2 cm / 30 inches away with a 3.2 cm / 1 1/4″ pipe or 304.8 cm / 10 feet away with a 10 cm / 4-inch pipe. If you aren’t sure where the plumbing vent pipe needs to be positioned, you should consult with a building inspector or a professional plumber. 

Let the Professional Plumbers Help 

You use your waste line every day, so make sure that your vent stacks are properly installed and maintained. This is one situation where you will want a professional plumber to take a closer look at your plumbing system. Clean Line offers professional plumbers in Winnipeg who can help you get your home plumbing set up properly. 

Contact us today to learn more about how we can help you make the most of your vent systems without violating building codes!