This is the exact situation that we had in our old home, but with very serious impact. The previous owner should have replaced the sewer pipe, (roots, collapsed orangeburg) but just kept snaking it out every year to save money. The end result is that the sewer pipe leaked so much water into the foundation under our dinning room that it has sunk about 2"! The cost to replace the sewer line was $3,000, plus it will now cost another $8K to relevel the diningroom.