If you need to install an air admittance valve, or AAV, to add pipe ventilation, it helps to have plumbing knowledge and the ability to shut off the main water valve to the area if necessary in an emergency. Also, make sure to check with the local authorities before you start, to verify that they accept the use of AAVs. This will help to avoid fines or having to do more work down the road.
An air admittance valve is a small mechanical device that helps provide airflow for trap seals, without the need for additional stack vent piping out the roof. If an AAV is an acceptable option, they can prevent the need to cut holes in walls, ceilings, attics, and roofs, thus saving much time and labor expense.
Complete kits are available at plumbing supply stores and online retailers for both large and small valves. Prices usually range from $25 to $50. Larger valves can support more than one unit (sink, shower), while smaller valves are designed to service only one unit at a time. Toilets, however, should always be vented to the outside, usually via a stack vent in the roof. This prevents odor and airborne disease problems from collecting inside the bathroom.
Step 1 - Prepare the Tools
Before taking any pipes apart, make sure to collect all necessary tools and have them nearby. If the work area is not well lit, a flashlight can be handy, and if there is enough room, an extra person to hold the light can be helpful. Old towels are useful to mop up any drips and save floors. Once the tools are assembled, turn off the water flow to the unit.
Step 2 - Place the AAV
The air admittance valve should be placed in an area that allows good physical access as well as free air flow. They are often fitted to the drain line, between the trap and the wall, generally at least 4 to 6 inches above the weer, which is the highest part of the trap where it turns lateral. Adapter pieces can be purchased to fit the pipe size if necessary. Make sure it is tightly secured in place with appropriate sealing tape or chemical welding materials.
Step 3 - Finalize the Process
Once the air admittance valve has been installed it should be tested. Turn the water supply back on, and then turn the water on in the sink or shower, or flush the toilet. Check for leaks and proper drainage. Listen for gurgling sounds. Watch for back-flow from one unit to another (i.e. flush the toilet and the water backs up into the sink basin).
If there are no strange noises or actions after several testing attempts, the valve is likely fitted properly and venting air as it should. If questions or concerns remain, it is always better to contact a professional plumber than experience sewage flooding.