The answer to 'drain foul smell' is that a foul odor coming from a drain is usually caused by a buildup of organic matter, bacteria, or sewer gas. Common symptoms include a persistent, unpleasant smell that may get worse over time. Some simple solutions include using a drain cleaner, baking soda and vinegar, or a plunger to clear the blockage. However, if the smell persists or the drain is slow to clear, it's best to call a professional plumber to diagnose and fix the underlying issue.
Foul drain odors can be caused by a variety of factors, such as food, hair, or soap scum buildup, a dried-out P-trap, or a sewer line blockage. These problems can lead to the release of sewer gases like methane and hydrogen sulfide, which have a distinct rotten egg smell. Ignoring the issue can lead to more serious problems like pipe corrosion or even a sewer backup.