The answer to 'why is my sump pump overflowing' is that the sump pump is not able to keep up with the amount of water entering the sump pit. This can be caused by a variety of issues, including a faulty or undersized sump pump, a blocked or clogged pump intake, a problem with the discharge line, or high groundwater levels.
If your sump pump is overflowing, you may notice water pooling around the sump pit or even water backing up into your basement. This is a serious issue that needs to be addressed quickly to prevent water damage and potential health hazards from moisture and mold.