A gurgling sound when your sink is draining could be the sign of several issues, not just a blockage in the pipes. The most likely culprit is an old or clogged check vent.
Check vents draw in air to allow water to drain freely through your pipes. If the check vent becomes clogged, this may cause your water to drain more slowly and produce gurgling sounds.
You can replace the check vent underneath your sink by simply removing it with pliers and replacing it with a new unit. To find the proper replacement, remove your check vent and bring it with you when you purchase another. Find a hardware store near you to get started.
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