When you wash water down a sink's drain, the water should flow smoothly down the drain pipe without incident. If your sink's drain gurgles as you wash water down it, a problem exists with how the drain pipe operates. Ignoring the problem will only increase the chances that the problem will worsen.
A clog in the sink's drain pipe may lead to gurgling. If the clog has not completely sealed off the drain pipe, it may trap air behind it, allowing the air to flow up the drain gradually and cause the gurgling. Use a plunger on the drain to force the clog loose. If the gurgling continues, place a bucket under the drain pipes, loosen the connections, and remove the drain pipe pieces. You will then need to feed a drain snake down the pipe in the wall to remove any clogs. Check the pipes as you reattach them under the sink, ensuring they do not have any clogs inside.
Proper venting of the drain pipes in your house will stop problems such as gurgling in your sink's drain. Your sink's drain may not be connected to a vent pipe, but first you must assume it is. An obstruction in the vent pipe connected to your sink's drain pipe will cause gurgling since new air will not flow into the plumbing as it should and sewer gasses cannot flow out of the vent pipe's opening.
You must go onto the roof to check the vent pipes. Look down each pipe with a flashlight so you can see if any debris has fallen inside. If you see debris in a pipe, use a long tool to pull the debris out or dislodge it. Use your hose to send water down the vent pipe, helping dislodge the stuck debris so the air can flow through the pipe normally. A high-pressure attachment on the end of your hose may help your chances of knocking the debris loose.
A local plumber will help you diagnose and solve the problem with the sink's gurgling. The plumber will inspect the drain pipe for the sink to determine if it attaches to a vent pipe and is sufficiently vented. The plumber also has the ability to locate debris blocking the vent pipe or damage to the vent pipe, which will cause the gurgling. A plumber also comes with a long auger or snake tool that will feed all the way through a vent pipe, enabling him to push out obstructions so the vent pipe works correctly.