Vent pipes, also known as plumbing vents, plumbing vents, or vent stacks, are the type of plumbing fixture that often confuses new homeowners. These devices are actually something that any home’s plumbing system has along with drain pipes, supply lines, waste water pipes and so on.
So what is a vent pipe, what does it do, how does it work and what do you need to know and do about it? Let’s explore all of these below.
What is a vent pipe?
Vent pipes are an essential part of any sewer and drainage system, even if they do not carry water or liquid. Conversely, while supply lines bring water into the home and drainage pipes remove wastewater, the ventilation system is which regulates the air pressure in your home’s plumbing system.
So, although we rarely think about them, if at all, a plumbing pipe or vent is what prevents sewer gas from building up, unpleasant odors from entering our homes, vacuums forming in drains and causing problems, and more others. .
Essentially, this simple standpipe is what makes everything in your home’s plumbing system work. However, there is more than one type of vent pipe, depending on the exact specifics of your system. Here are the basics you need to know about each type.
Different types of vent pipes for plumbing
1. True ventilation
True vents are the most basic and common type of vent pipes for plumbing – are simple vertical pipes that start from your downspout line and go up to the roof, where they exhaust all the excess air from your plumbing system.
Because they are vertical, no water flows through them and only air comes out of them. However, they can easily get blocked by bird nests, leaves and other debris, which is the main thing to watch out for with them – more on that below.
2. Common ventilation
Even though they are called «common vents», they are not what we commonly call vents. Instead, this type of vent connects two separate fixtures that have been installed on opposite sides of a wall, such as a sink with a tub or toilet and so on.
The two fixtures are usually connected to the vent stack with a sanitary cross, and the purpose of this vent is to regulate the air that flows between the two fixtures and help guide it to the true vent and out of your home .
3. AAV – air intake valve
Air intake valves they are special holes that open whenever the sewage system starts to leak. The purpose of the AAV is to let air inside the plumbing system and thus use gravity to prevent harmful gases from escaping from the plumbing system and into your home.
4. Auxiliary ventilation
An auxiliary vent or a vent pipe is the type of vent stack that is placed behind fixtures and drain lines. Its purpose is simply to run and connect to the true vent, similar to how regular vents work.
As you can see, what we call «true venting» is really the main and basic type of venting we’re talking about here, with most of the other subtypes only working to support true venting and help guide air to it. AAV valves are an exception because they work in the opposite way – they let air balance the system rather than letting air in and out.
Blocked vents and other ventilation issues to watch out for
The main problem you should watch out for with vent lines is a blocked vent. This often happens with the main roof vent, but debris of all kinds can cause traps and blockages along the drain line and vents connected to it.
If a vent blockage occurs anywhere in your plumbing system, you can expect to see any of the following 7 signs:
- Less water pressure coming from the supply pipes because the clogged vent prevents air from escaping and excess air in the plumbing keeps the water in the pipes stagnant.
- Also, the lower pressure in the sewer drains for the same reason – stagnant water due to excess air in the system.
- Gurgling sounds come from your plumbing system because both water and air are having trouble moving through your plumbing system.
- Drains back up sewage – this happens because the air and water pressure in your system is so high that the water has nowhere to go but back down the drain.
- The drain cleaning system cannot solve water pressure problems. Most of the time we reach for the plunger or drain cleaner when we have water pressure problems because we suspect debris has clogged the drain itself and not the vent lines. If the latter is the case, however, a simple drain cleaner won’t help because there’s nothing to clean in the drain—it’s just water and air.
- Empty and dry toilet tanks – we’re used to this happening from a leaking toilet tank, but the same thing can happen if you have a clogged air line. So if the water in your water tank has suddenly started to drop or has disappeared completely and there are no leaks that could have caused the problem – consider checking for a blocked vent pipe instead.
- Bad smells coming out of your plumbing system – clogging and blockages of any kind can cause a bad smell to come out of your drains and the same thing happens after a blocked vent pipe. Worse, these noxious gases are often not only unpleasant, but dangerous to your and your family’s health.
Some examples of such gases are ammonia and hydrogen sulfate with their disgusting smell of rotten eggs. Another example of such a dangerous sewer gas is methane – it’s both colorless and odorless, so you can’t catch it yourself. However, it will often be accompanied by other odors, so that’s all the more reason to act right away.
That’s why it’s ideal to never let it get that bad and act on any of the other signs on this list. If you missed them though and an unpleasant smell started coming from your ducts, it is important to act immediately and call a professional plumber.
Aside from blockages in the vents, other occasional problems you may encounter are things like rust and cracking, but these are rarer and less impactful. When it comes to installing vents, blockages and clogging are really the main things to watch out for.
How to maintain, prevent and deal with pipe vent blockages?
Unfortunately, depending on how your system is set up, there may be very little you can do yourself other than call in a professional installer. Most blockages in the ductwork vent system occur near the top of the true vent, meaning on the roof of your home. If that area is easily and safely accessible, then you should be able to go there and check for debris, bird nests, piles of leaves, and other possible problems.
In the simplest cases, clearing a true vent clog it can be as easy as poking the vent with a long stick or cleaning it with a water hose. In other cases, however, you may need some more professional equipment.
If, however, your roof is not accessible, or if it is, but is not secure, it is recommended that you contact a professional installer. Such services can be expensive depending on where you live, but they can make the whole process a lot easier, save you a lot of time and effort, and eliminate any risk of falling off the roof.
As for maintenance and preventing blockages – this is really more a matter of putting the appropriate covers on the pipe vent so it doesn’t collect leaves, debris and bird nests. If there is such a thing, there should be almost 0% risk of problems. From there, it’s just a matter of keeping an eye out for any of the 7 signs of trouble above.
Bottom line – what is a vent pipe?
Vent pipes are a must in any proper plumbing installation as they allow all the other individual vents to work properly and provide adequate water flow into your home as well as remove waste water without any problem. Vent pipes do this by regulating the air inside the plumbing system and preventing voids and other air-related problems.
However, these vents or vent stacks are not guaranteed to remain trouble-free and require good maintenance as well. So, if you want to avoid air blockages, negative pressure, or other problems that require an expensive visit from a professional plumber, it’s a good idea to take care of your vent lines.
