While it's left to the homeowner to decide when to replace the drain line, some common reasons for a replacement are: • Repeated blocked and clogged drains needing frequent repair • The sewer system is over 30 years old and has worn out with time and use. • Chemical drains cleaners can with time war out and corrode sewers. Your plumber is the best person to assess your drainage and sewage system to determine if it should be replaced or not.