One solution is an air admittance valve or AAV.
Then gravity closes the valve, keeping sewer gases out of the room.
Depending on the valve and the size of the vent, AAVs can support one or multiplevent lines.
Credit: Jay Wilde
Air admittance valves are operated by gravity.
When water and waste move down a drain line, it creates negative air pressure in the pipe.
When the negative pressure ceases, the sealing washer falls back in place.
Credit:BHG / Michela Buttignol
Earlier versions of this gadget were spring-operated.
Such units are still available but are unreliable and don’t meet code in most areas.
The unit must be placed perlocal codesand the manufacturer’s instructions.
The appropriate coupling for the AAV (glued or threaded) attaches to the tee.
Check the manufacturer’s instructions and local codes to determine the proper height for the AAV above the drain.
Look to the manufacturer’s directions if you need additional assistance.
AAVs must always be installed vertically and should be unobstructed from items under the sink.
Credit: Illustration by Art Rep Services, Inc.
