A Guide to Plumbing Vents for Chicago Residents

Michael Tobias
5 Minutes Read
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    A vent piping, by definition, is a network of vents and drainage pipes that aid in maintaining air pressure within the drainage system. A number of people have heard the term “Drain Waste Vent Piping System” before, but don’t really know what it means. To begin with, for a waste drainage system to work properly and efficiently, vent pipes are employed, as they avoid evacuation of air and prevent sewer gasses from entering the building. Many plumbing systems require these vents, including sewage ejector pumps and basins.

    Most vents are incorporated together with drains and wastage dumps in a “Drain-Waste-Vent System”, or DWV. You can basically consider the DWV as the entire network of pipes and vents that keep all the sewage and grey-water away from your house.

    What Does The Chicago Plumbing Code Say About Vent Installation?

    I managed to narrow down the basics of Chicago Plumbing Code to 3 main general rules for installing and maintaining a plumbing vent system.

    • Every System Must Have A Vent:

    In general, every plumbing system shall have a vent system which is sufficient enough so that the pressure is no more than 294 Pascals. Furthermore, vents are not necessarily required for downspout traps or basement floor drains.

    • Slope And Thickness Of Pipes:

    The pipes must have a specific slope and thickness based on the type and requirement. To be more specific, the Code allows the pipes to be anywhere between 1 and a half inches and 6 inches thick. The slope should never be less than a quarter inch per feet, and no more than one-sixteenth inch per feet.

    • Vent Materials:

    Last but not least, the vents must be made of specified material. Every vent must be covered with an impervious metal to prevent water damage, leaks, and weather corrosion (known as “flashing”). If copper is used, it shall weigh above 2.5 kilograms per square meter. For lead flashing, the lead shall not weigh less than 15 kilograms for every square meter.

    Install a plumbing vent through a professional.

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    What Does A Plumbing Vent Do?

    A plumbing vent performs a number of functions, including:

    • Regulates Air Pressure:

    Take a soda can. Now suck all the air out of it. The can will get crushed. Now imagine if the air wasn’t air but rather regular water. Usually, water flows out and air takes its place. But in a closed system, such as a drainage pipe, there is little to no air. This creates a vacuum, and the pipes are prone to crushing, bursting, or going in backflow to fill the gap.

    This is where plumbing vents come in. By allowing a passage for air to flow, they allow the drain pipes to suck in air from outside and remove the vacuum or backflow which would have otherwise resulted.

    • Evacuates Sewer Gasses:

    The problem with sewer water isn't just the water. The excrement and sludge in the water release a pungent smell. This smell, if allowed to enter a building, can cause nausea, various diseases, and be a really big inconvenience. Sewer vents not only allow airflow, but they also allow the gasses to escape to the outdoors without ever reaching the residents.

    • Allows Easy Uninterrupted Flow:

    Imagine a bottle turned upside down with its cap closed. Open the cap and let the water flow out. You will notice the water coming out in “packets”, with breaks in between. And if you look closely, large bubbles of air can be seen flowing from the mouth to the back. This is because, as the water flows out, the space left behind must be filled with air to avoid creating a vacuum.

    Now cut a hole in the back of the bottle. The water will flow out smoothly. This is because the air is now being sucked in from the hole and no longer from the mouth. Vents provide the same convenience. They allow the draining water to suck up air from outside, instead of from the mouth of the pipe.

    Why Should I Worry About A Malfunctioning Vent?

    If you’re not careful, a malfunctioning or broken vent can be pretty dangerous, if not annoying. Lack of a plumbing vent can:

    • Cause a vacuum in the plumbing system.
    • Force backflow.
    • Burst or explode sewage pipes.
    • Malfunction other utilities attached to the pipes, such as ejector pumps and sanitation equipment.
    • Accumulate sewer gasses, which are repugnant and unsanitary.
    • Create clogs and sludge by not allowing the airborne particles to escape properly.
    • Gradually sucks up more water from the sewage utilities.

    How to Identify and Fix Clogged Vent Pipings:


    Vent pipe clogs are caused by:

    • Lack of maintenance, which can lead to a slow buildup of sludge and excrement.
    • Leaves or debris entering the pipes.
    • Snow building up at the very mouth of the vent.
    • Leakages from other pipelines or sewage lines.
    • Frozen pipes.


    The following signs are the first symptoms of a clogged vent:

    • Water is being gradually drained from sinks, toilets, baths, and the floor.
    • Pungent odors that seem to emanate from the drains or open pipes.
    • Water is not being drained at all and seems to be standing above the drain.
    • Gurgling or bubbling sound when water is going down sink.

    How To Fix The Problem:

    Fixing the problem usually depends on how the problem is caused. If you can't call a plumber over to help with the clog, then consider taking the following actions as a temporary measure:

    • Manually remove the pipe with the clog and thoroughly wash it. Use a long stick or rod to push the clogged mass out of the pipe.
    • If the problem is caused by snow, remove the snow or slowly heat the pipe to melt the snow and let it wash out with the rest of the sewage.
    • If there is a leakage from other pipes, then first fix those pipes with sealant or cement. This can be pretty technical, so have a professional do it.
    • If the pipes are frozen, slowly heat them to defrost.

    Caution: Sewer gasses in the vents may be flammable. Do not heat past combustion.


    We have to admit the Plumbing code of Chicago has set a lot of rules into place. But these are only to keep us safe. Vent piping is no doubt the most neglected and overlooked utility. But they are extremely important. Without them, the entire Drain-Waste system would crumble.

    Well, now you know all about vent pipes. Keep in mind that plumbing work is extremely intricate, and it’s best when done by a professional.

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    Tags : Plumbing Engineering plumbing design plumbing issues Chicago vent piping

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