The answer to 'why is my sewer line constantly running' is that there is likely a blockage or leak in the sewer line. A constantly running sewer line is a sign of a problem that needs to be addressed quickly to prevent further damage and costly repairs.
Some common causes of a constantly running sewer line include tree roots growing into the line, a broken or cracked pipe, a buildup of debris and waste, or a problem with the sewer line connection. Symptoms may include slow draining sinks and toilets, foul odors, and even sewage backups into the home.