An overtaxed sewer main while having heavy rain could be caused by a number of things. Roof downspouts draining too close to the house, a problem with the perimeter or foundation drains, problems with a sump-pump, a blockage of the main, etc. could be the cause (all are examples of internal plumbing problems). An overtaxed sewer main due to the heavy rain or a blockage of the main could also be the cause. Although we may not be able to determine the exact cause of the problem, Sewer Maintenance can determine if it is being caused by a problem with the sewer main, or if it is an internal plumbing problem.