Things You'll Need
Drain pipe T-fitting
Plumber's thread tape
Plumbers install mechanical plumbing vents in situations where an open-air vent system will not work, such as under a kitchen island's sink. A mechanical plumbing vent, sometimes referred to as an air admittance valve, or AAV, allows fresh air to enter the drain pipe without releasing sewer gas. Without proper ventilation, water flowing through a drain creates a vacuum in the pipe. The vacuum pulls air through the drain trap, making the drain gurgle. Installing a mechanical plumbing vent usually solves this problem.
Cut off the building's drain pipe about 4 inches from the wall with a hacksaw. Plumbers install mechanical plumbing vents in open-air areas, such as in a cabinet.
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Attach one of the horizontal ports on a drain pipe T-fitting to the building's drain pipe, using PVC adhesive to weld the fitting to the pipe. The T-fitting has two horizontal ports and a vertical port. The T-fitting's vertical port must face upward.
Insert the sink drain's drain-trap fitting into the T-fitting's second horizontal port, using the PVC adhesive to bond the fittings together.
Glue the proper mechanical plumbing vent adapter into the T-fitting's vertical port, using the PVC adhesive to secure the fitting and adapter together. If the mechanical plumbing vent has male threads, glue a female adapter into the T-fitting's port. If the mechanical plumbing vent has female threads, glue a male adapter into the T-fitting's port.
Cover the male adapter or mechanical plumbing vent's male threads with a plumber's thread tape.
Spin the mechanical plumbing vent's threads onto the adapter's threads, turning the vent clockwise with a hand. Hand tighten the vent.
Turn the mechanical plumbing vent clockwise one full turn with locking pliers.
Not all local building codes allow mechanical plumbing valves.