What are plumbing vents, and why do you need them? In short, to keep the stink out!

The plumbing system in your home is designed to remove waste and wastewater efficiently from your house. It has two different systems, a drainage system and a vent system, that work together to do so.

Every plumbing fixture in your home (your toilets, showers, sinks, etc.) not only has a waste pipe that leads the wastewater away from your home into a sewer system, but it also has a plumbing vent pipe, commonly referred to as a vent stack, that provides fresh air into that waste system to help water flow smoothly through the drainage pipes and removes gas and odors up and out of the house each time a toilet is flushed or a sink is drained.

It can be a bit confusing because when someone says “vent,” you typically think of a bathroom fan. That is a vent as well, but this is a pipe that specifically ventilates the plumbing waste system. A good analogy for how a plumbing vent works is if you imagine sticking a straw into a glass of water. When you put your finger on the top of the straw and lift the straw out of the water, the straw will remain full of water. Once you release your finger from the top, the water will flow out of the straw. That is how the pressure remains equalized. The fresh air vent in the waste system allows for the pressure to ensure all of the wastewater goes down and out of the house.

No water runs through the plumbing vent pipe. In that part of the waste system, there is also a water seal trap (P-trap) attached to each fixture. The vented air helps to equalize the pressure on both sides of that trap so that the water in the trap does not get siphoned out. It aids in how well the drain part of the fixture is working. The fixture cannot drain effectively if there are no vent pipes connected to them. For example, in a bathroom fixture group, if you flush the toilet and there is no vent to that toilet, or the vent is not working properly, it may suck the water out of the trap on the bathtub. This will cause the bathtub trap to become dry, and you can sometimes hear a gurgling noise from the drain. Also, if one of the traps is not full of water anymore, it will not stop the sewer gas from coming into your home, and you may start to smell a foul odor.

These vent pipes you do not see. They are concealed in the walls and ceilings of your home, and they terminate through the roof. Each vent pipe does not need its own separate line to the roof. Most times, your house has one or two main roof vents, and the rest of the vents join together inside of the walls and the attic to the main penetration through the roof. All piping systems, whether they are water piping, waste piping, or vent piping are engineered correctly so that they work properly. A licensed plumber knows how to size each vent pipe.

St Paul Pipeworks Vent Pipe

St Paul Pipeworks goes the extra mile to make sure all of its customers’ plumbing needs are satisfied. If you are looking for a quality plumber in the St. Paul and Minneapolis metro area, give St Paul Pipeworks a call today.

Yours Truly,
Matthew Dettwiler
Social Media Manager

Why do you need plumbing vents? – Ask a Plumber