Plumbing fixtures like a sink or a bathtub have a trap filled with water to prevent harmful gases from entering the house. The trap requires ventilation that prevents water from leaking out of the trap, but allows the drain to flow freely. A air inlet valve allows air to enter the drain pipe without a ventilation fitting and is useful when a connection to a ventilation pipe is impractical or impossible. The valve allows air to enter the drain pipe and prevents the gases from escaping.
Wrap Teflon tape on the thread of the PVC siphon adapter. The trap adapter is the connection to the drain pipe that exits the wall under the sink. Screw the appropriate PVC threaded t into the trap adapter until it is tight, then enough to point either left turn or right. Use the sliding joint pliers to activate the tee connection if necessary.
Cut a piece of PVC tubing long enough to reach out of the tee fitting on the left or right edge of the sink. Open the first PVC can and clean the dauber attached to the top at both ends of the pipe to apply the primer. Submerge the constructors in the first after each application. Apply a primer for the inside of the male adapter connection and inside the 90 degree elbow connection.
Open the PVC cement can and remove the dauber. Clean the washer from around one end of the tubing and into the male adapter connection. Place the adapter over the final cementing of the PVC pipe and rotate a quarter turn. Hold the accessory in place for 30 seconds. Repeat this step for the 90 degree elbow and the other end of the pipe.
Cut a long piece of 1 1/2 inches of PVC pipe. Apply a primer to the ends of the tubing and the interior of the second male adapter connection. Apply cement to the other end of the 90 degree connection and one end of the 1 1/2 inch long tubing. Fit the end of the cemented tubing into the 90 degree mount. Apply the cement at the opposite end of the tube and the inside of the male adapter fitting secondly and they fit together.
Wrap the threads on the male adapter at the end of the pipe with Teflon tape. Screw the connector on the left or toward the thread of the Tee connection until it is firm. Rotate the tube one additional turn to point the short piece of tubing and male adapter up.
Cut a long piece of 4 inches of PVC pipe. Prime the ends of the tubing and the inside of two female adapter connectors. A female adapter at each end of the cement pipe. Wrap the threads in the air intake valve with Teflon tape. Screw the valve on one of the female adapters until it is firmly tightened by hand.
Wrap the threads of the male adapter attachment attached to the 1 1/2 inch long piece of the tube with Teflon tape. Screw the female mount into the long 4-inch piece of tube into the male adapter until it is firm. Use the torpedo level to secure the vertical level tube and adjust the long tube connection with tweezers if necessary.
Wrap the threads of the male threaded adapter with Teflon tape and screw into the mounting tee until it is tightened, then turn it an additional half turn with the pliers. Install the siphon assembly into the sink drain and trap adapter by the manufacturer’s instructions.
Tips & Warnings
The long 4 inch tube should be within 15 degrees of the vertical level or the valve will not work properly. It does not have to be perfectly level, but it should be close.
The fumes from the cement and primer are dangerous in enclosed small areas. Keep lids screwed on cans whenever you are not using them and read safety instructions before use.