The answer to 'drain trap overflowing' is that a clogged or blocked drain trap is the most common cause. The drain trap is the curved section of pipe under a sink or bathtub that is designed to hold water and prevent sewer gases from entering your home. When this trap becomes blocked, water can back up and overflow.
Some common symptoms of an overflowing drain trap include slow draining water, foul odors, and water pooling around the fixture. Causes can include hair, soap scum, and other debris buildup, as well as a broken or damaged trap. In many cases, you can fix this issue with some basic DIY plumbing work, but more severe blockages or damage may require calling a professional plumber.