All plumbing systems contain negative air pressure inside the drain pipes, which prevents water and other waste from moving down the pipe properly. But plumbing vents allow air into the system, and create positive air pressure that allows water to move quickly down pipes. Without air vents, your plumbing would be backed up all the time. The most common types of plumbing vents are vent stacks, which run from the drain to the roof of the house. However, in certain applications such as plumbing a kitchen island, automatic air vents are often allowed by local plumbing codes. These devices act as a check valve, allowing air in but not allowing gases to escape the pipe. The automatic vents sit on the back of the P-trap on the drain.
Things You'll Need
- Air admittance valve (automatic air vent)
- Plumber's tape
Place the pliers around the square nut that protrudes from the top of the cap on the back of the P-trap. Turn the cap counterclockwise to remove it, exposing the top of the T-pipe on the back of the trap.
Wrap the pipe threads on the base of the automatic air valve with two layers of plumber's tape. This will help lubricate and seal the connection between the air vent and the P-trap.
Place the air valve into the top of the T-pipe on the back of the P-trap and screw it in by hand until tight.
Turn on the water and make sure the liquid drains properly. You should hear a slight rushing of air from the automatic air vent while the water is draining.
Tips & Warnings
- Check your local plumbing codes to see whether automatic air valves are allowed for you specific application.
- Make sure the air valve is tightly screwed into place to avoid allowing gases to escape from the seals around the valve.
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