We installed a new mounded septic system in the back yard of our church parsonage this past June. Since then, significant rainfall causes odor to back up into the house. There are two bathrooms in the house, one in the basement, and one on the second floor. The problem seems to originate when the second floor bathroom gets used.
Is this a design problem, or something that will improve with time as the system matures?
Should the designing engineer be called in? How should it be tested?
Thanks for your help!!