Air Admittance Valve

How to Install an Air Admittance Valve for a Sink


Wastewater pipes are usually set at a slight angle as this encourages the water to drain away naturally. However, there is more to water movement than gravity.  When water fills a pipe, gases cannot move through it. That means that the air is pushed in front of the water and a vacuum is created behind. When this happens the pressure can build up enough that the water stops flowing in one direction and returns the way it came. It will seem like you have a clog and need the assistance of a good emergency plumber. The only way to prevent this from happening is to make sure that enough air is coming in behind the water to keep it flowing smoothly and prevent a vacuum.  That’s why modern plumbing systems have vent lines. The vent allows air into the pipes and allows everything to work smoothly. Unfortunately, when you are creating or remodeling a kitchen it can be hard to add vent pipes in the right places. There is often a structural issue that prevents it from being possible. Fortunately, there is a solution, the AAV-Air Admittance Valve


How The Air Admittance valve Works

A standard vent pipe goes runs up the house and past the roofline, allowing air in or gases out and maintaining balance in the system. If you can’t connect to the vent pipe then the AAV steps in. It’s a small valve that can be fitted to your plumbing. In short, it allows air into the system to aid the drainage of appliances and then closes to prevent gases from escaping into your home.

The valve is fitted near the appliance that needs help draining and is operated by gravity and air pressure.

When water is draining the air pressure in the pipes drops, allowing the valve to fall open and let air in. As soon as pressure is equalized the valve closes again.

Installing An Air Admittance Valve

You will need to check your local codes to ensure you are complying with them in regards to where you position your AAV. The best location is straight after the sink drain. 

Under the sink you’ll see a ‘P’ trap, this ensures water is retained and gases don’t rise into the sink. There will usually be a short ruin before the wastewater drops into the main drain. 

This is where you fit the AAV. All you need to do is remove the 90° bend in your current waste pipe and attach a Y connection. This maintains the flow of wastewater and creates a small upward section where you can install the AAV. You can add a Y connector to any part of this stretch of the waste pipe and it will perform the same function.

Once it is secured in place it will start working straight away. Best of all, because it works via gravity there is virtually no maintenance to worry about. The AAV is discreet, works silently, and will transform the efficiency of your sink drainage. 


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