Some plumbing jobs, like adding a sink or a basement bathroom, make it hard to reach the main vent stack. In these cases, plumbers may suggest using air admittance valves to let air into the drain system without running a full vent pipe.
We’ve worked with air admittance valves in remodels and tight spots. They can help, but they also fail more often than most people expect. Sewer smells and poor drainage are common signs. Here’s what to know before choosing one for your home.
What Does an Air Admittance Valve Do?
An air admittance valve (AAV) is a one-way valve. It lets air into your plumbing line when water flows, but it won’t let sewer gas out. But why is venting important?
Plumbing systems need airflow to work properly. When water moves through pipes, it creates suction that must be balanced with air. If no air gets in, the water may gurgle or drain slowly. That’s why homes use vent pipes that go up through the roof.
But if you’re adding a sink or moving plumbing far from that vent, you may need another way to let air in.
When Do You Use an Air Admittance Valve?
We usually see air admittance valves used in these cases:
- Kitchen islands with no nearby wall vent
- Basement bathrooms added after the house was built
- Laundry rooms moved to a new location
- Kitchen remodels where the sink changes spots
AAVs make these jobs easier because you don’t need to open walls or run long vent lines. But they come with risks.
Pros of Air Admittance Valves
When used correctly, air admittance valves can help in tight situations.
- Saves time and money: No need to run a pipe through the roof
- Less wall damage: You avoid opening finished drywall
- Easy to install: Great for quick remodels or small plumbing jobs
- Takes up little space: Fits under cabinets or behind walls
Pro Tip: AAVs must be installed in accessible places. Never hide them behind sealed walls or ceilings.
Need expert help with your plumbing venting? Contact Dick Ray for a free consultation. We’ll inspect your setup and give you safe, lasting solutions.
Problems with Air Admittance Valves
Even though they work at first, air admittance valves are mechanical parts. And like any moving part, they wear out. Here are some reasons why air admittance valves fail:
- Rubber flapper wears out: Over time, the seal inside breaks down
- Leaks and odors: When the valve fails, sewer gas enters the home
- Wrong use with pumps: If your system uses a pump, it needs to push air out, which an AAV can’t handle
- Incorrect height: If installed too low, they won’t work during heavy flow
- Poor location: Some people install them in attics or behind walls, where you can’t see or smell problems right away
Key Takeaway: Air admittance valves should not be used in systems with pumps, such as laundry pits or dishwashers that push out waste.
Common Air Admittance Valve Mistakes
Even when AAVs are allowed, we see problems when they’re installed wrong. Below are some mistakes we’ve seen:
- Installed under a sink but not high enough above the drain
- Tucked inside a wall, which makes it hard to detect failures
- Used with dishwashers or pumps, which creates backpressure
Our Take on Air Admittance Valves
We don’t recommend air admittance valves unless there’s no other option. Even then, they must be used with care.
If you can’t reach your old vent pipe, it’s better to run a new pipe to tie into a vent that goes to the roof. That keeps sewer gases out and your system drains properly.
Final Thoughts: Are Air Admittance Valves Worth It?
Air admittance valves are a short-term fix. They have a purpose, but they’re not always reliable. We’ve seen too many homes with sewer smells caused by failed valves. If you want a permanent, worry-free venting setup, tie back into your main vent system.
Want it done right the first time? Call Dick Ray for expert plumbing work that lasts. We’ll help you make the best choice for your home.
