What upkeep? Is your house real old?
The upkeep expense is on the sewer lines. They all had to be replaced with new pipes to the street and the town building inspector has to approve of an (expensive) engineering plan. They can back up if the main lines get overwhelmed in storms. Every government that exists can pass upgrades that have to be paid for and create new standards that must be met. I never had problems with septic, as I was careful about what went down the drain.