What Are  Plumbing Vents?
& Why Do You Need Them?

Sometimes referred to as plumbing air vents or vent stacks, a property's plumbing vent system does not handle water, even though it operates as part of the overall plumbing system. Most modern plumbing systems comprise water drainage capabilities combined with a ventilation system. A sewage vent pipe typically runs vertically out through a property’s roof, doubling as both a point for air to air to enter and for unwanted gases and odours to be expelled. 

A toilet vent pipe is a crucial element in the system that helps regulate air pressure within it and maintain the flow. No plumbing fixture that flushes or guides water to different areas of the home can operate without this air pressure to propel the liquid. Without a vent pipe on the roof, the system creates a vacuum, leading to sluggish or non-existent drainage.

Another excellent feature of a vent pipe is that it removes noxious gases that can make their way from the sewer into your home. These gases smell foul, are highly flammable, and can be dangerous to health, causing nausea, dizziness, headaches, and fatigue.

P-traps

A P-trap pipe is named because it looks like the letter ‘P’ facing downwards. Its primary function is to prevent sewer gases from entering your property by creating an airtight seal and holding enough water in the curved section of the P to prevent gas from penetrating. One arm of the pipe is connected to your home's sewer vent pipe, which allows the gas to escape into the atmosphere. A bonus feature of this system is that no foreign objects or creatures can enter your system this way, and it will also catch any items like rings that you accidentally drop down the sink.

A sewage vent pipe is typically found in one of three forms, namely:

• Common vent — When opposite sides of the same wall have plumbing fixtures in place, they are linked to the flue by what is known as a ‘sanitary cross’.
• Auxiliary vent — A pipe that runs upwards and over the feature to join the system’s common vent, usually attached to the drain line or behind the fixture itself.
• True vent: Despite the name of its rival above, this is the most common type of toilet vent. Attached to the drain line, it can vent directly through the roof because it contains no water.

If a vent pipe becomes blocked, it will cause negative pressure to build up inside the plumbing system. This interrupts or seriously reduces the flow of water. Some signs that you may have a blocked plumbing vent pipe include:

• Slow water drainage
• Thoroughly clearing your water drain has little or no effect.
• Unpleasant smells come into the property through the drains. This means your P-trap is probably waterless due to the negative pressure.
• When running water elsewhere in the property, you can hear gurgling sounds from different pipes and drains. Typically, this is due to the air being sucked out of the P-trap.
• Stagnant water in sinks and baths that will not drain.