When purchasing a home you should have had an inspection clause in the PA for the home and the septic field. It is best to always have the home inspections done no matter what the seller discloses or not. You should have been given a sellers disclosure prior to writing an offer. What does the disclosure say about the septic system? If the seller and agent said it was in good shape you should have gotten that in writing. When was field installed? Has it ever been replaced? Has it ever been service? These are some of the questions that should have been ask and answered? Another factor that may have helped, did you have a buyer agent to work in your best interest. Bad on that agents part not to recommend the inspections. Basically, your only recourse is to take them to court. Best of luck!