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

Does your home have a sewer vent pipe? Does it need one? What do they do? Dr Leak has all the answers you need, and this article examines this element of your plumbing system, offering practical tips and advice on their types, installation, sewer vent pipe regulations in Australia, and how to deal with blockages.

What is a plumbing vent system, and why would you need one?

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.

The primary purposes of a plumbing vent pipe

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.


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.

Signs that your sewer vent pipe may be blocked

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.

Dealing with a blocked toilet vent

Modern plumbing techniques use all the available technology to get the job done, and in the case of a blocked toilet vent pipe, cameras on flexible rods are the tool of choice. This provides a live feed that trained technicians can analyse, helping them to choose the best solution to the problem. You cannot attempt to fix a blocked sewer vent by yourself using DIY, so do not hesitate to contact the experts at Dr Leak if you experience any of the indications noted above.

Whether you need a plumber in Melbourne or roof and gutter leak repairs in Sydney, we're ready to assist and handle the situation quickly and cost-effectively. Although the water supplied by WaterNSW is typically of excellent clarity and cleanliness, should you experience discoloured water or other plumbing issues, don't delay; call Dr Leak and let us sort the problem for you quickly and efficiently.

Why choose Dr Leak?

When only fully accredited, licensed, and skilled plumbers will do, contact Dr Leak Plumbing and let us provide the solution you need. We accept plumbing challenges of any size or complexity and pride ourselves on the following:

  • Fair, transparent pricing
  • Rapid call-out responses
  • The highest standards of materials and craft
  • 24/7, same-day service and emergency assistance
  • No call-out fee when booking before 17:00 (5 pm)
  • A lifetime labour warranty
  • Focused, highly-trained specialist technicians
  • Clean working practices and no dirty footprints left behind
  • Friendly, courteous staff
  • Interest-free payment plans (6 months)
  • Discounts for booking online

Dr. Leak’s founder puts great value on the contributions of our older generations, and we offer special discounts for seniors in an attempt to give a little back. Our clients' satisfaction is of utmost importance to us, and we never do anything to compromise our impeccable standards or cut corners. You only have to glance at our reviews to see how much people value our efforts, and we strive to improve them every day, from the simplest leaking taps in Sydney to complete plumbing system overhauls.

Contact us

Please take a moment to read our informative blog, and do not hesitate to contact us when you're ready to meet the team. We are standing by to address your questions and comments and give you all the advice and guidance you need. When you engage the services of the Dr Leak team, whether you need tap repairs in Melbourne or a plumber in Sydney, you can relax knowing you're in safe hands.

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