Kitchen sink vent plumbing helps the water to flow freely to allow air to move behind the water. Without a vent, water does not flow easily because it creates a vacuum behind itself. This requires each device to have a vent at a distance from the trap. Bathroom Sink drains employ various types of plumbing vents. A standard kitchen sink vent plugs directly into the drain pipe with a fixture shirt. The drain moves downward, while the vent tube moves upwards.
Kitchen sink vent are a special problem because there is no room for ventilation drainage. To resolve this problem, make a loop vent on the island. The top of the loop must be as high as possible under the sink. Both legs of the loop attached to a drain line under the ground, but one leg immediately installed below ground and above the evacuation line to tee ventilation. Attach your horizontal venting line for this shirt and run to the nearest vent. You need your horizontal venting tube 1/4 inch rise per foot off the tee vent for vertical ventilation, and any horizontal drainage pipe to fall 1 / 4 inch per foot. Consult your local plumbing code the specific municipal regulations.