What Are the Effects of a Clogged Plumbing Vent


Your plumbing vent is a critical component to having a properly functioning plumbing system. Occasionally these vents may become clogged with leaves, ice or other material, which prevents them from working effectively. If the clog is not cleaned away, your plumbing may be damaged or you risk harmful exposure to toxic gases.

About Plumbing Vents

  • All plumbing must be vented, which is typically done with a vent stack that protrudes from your roof and vents sewer gas out of your home, helping to balance the pressure in your plumbing system. Every fixture is connected to a plumbing vent; some homes have more than one, and each of these fixtures has a P-trap that holds water to prevent harmful sewer gas from entering your home. If the plumbing is not vented, each time a drain is emptied, this water that is necessary in the traps is sucked away as well, leaving them empty. The reason a plumbing vent is typically located on your roof is because the gases need to escape so that they can’t reenter through windows or other vents.

Toilet Traps

  • A sewer pipe maintains neutral air pressure when water is not flowing through it. When the waste water does flow, the air becomes compressed and creates positive pressure, which must be released or it will push against the flow of waste. The pipes require air behind the flow as well or negative pressure will form and create suction. When the plumbing vent is clogged, the toilet is usually the first affected fixture because it has the shortest trap. The water in the bowl empties because of the suction created, which leads to sewer gas entering your home through the empty toilet trap. Waste water pushed back because of a clogged vent can also damage your toilet trap, and then not only will the vent need to be cleaned ou,t but a new trap will have to be installed as well to prevent sewer gas from escaping.

Slow Drainage

  • One of the first signs of a clogged plumbing vent is slow drainage. Drains require venting to drain properly. Without a working vent, the fixtures can’t breathe and the waste water cannot be carried away. If your sinks drain slowly, the cause may not be a clog in the drain itself, but the plumbing vent. As food particles and other waste material lingers in the drains, the gunk may begin to build up along the sides of the pipes as well.

Sewer Gas

  • Plumbing vents remove sewer gas from inside your home and safely expel it outside. If the vent becomes clogged, it cannot do this job. Sewer gas may be present in small, harmless levels in most homes. It forms as household waste decays and contains toxic gases such as hydrogen sulphide, methane, carbon dioxide and nitrous oxides. When a clogged plumbing vent is not repaired, these and other toxic gases can be released through your floor drains and other plumbing fixtures. Long-term exposure to high levels of sewer gas can lead to hydrogen sulfide poisoning, asphyxiation due to the high levels of methane in an enclosed area, and also a risk of fire because these are highly flammable gases. The rotten egg odor is unmistakable. If you experience symptoms such as dizziness, nausea, and headache, seek medical attention and get your plumbing vent checked by a plumber.

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