Sellers May Have Violated Contract

Wondering if I have any recourse for this. I am a first time home buyer. I used a USDA loan. I had an inspection and it came back that the septic system was backed up and needed pump/repaired. It looks like the sellers hadn’t pumped it in almost 5 years.

In my contract I had it stated that “sellers must pump septic and have septic/plumbing company make all repairs so it works properly and passes inspections”

I did not find out until the day of closing that the old septic system had failed and that the sellers installed a holding tank instead of septic system. Technically the replacement passed the re-inspection but it’s also not the same system. I’ve never had a septic system as I’ve always lived in town but from my understanding this would mean it needs pumped often. Like SUPER often which is very expensive and highly inconvenient compared to the old system I thought I was moving into.

The sellers offered me a $3000 check to cover pumping costs but only wrote a check for $2500. Additionally I didn’t quite realize just how often and how expensive this will be compared to the system that was previously in place.

Do I have any recourse to sue the sellers and have them pay for proper replacement system? Would I be wasting my money on a lawyer instead of replacing it myself? I had no say in their choice to put in a totally different system and was not informed until the day of closing (3 days ago). Or am I completely screwed?

I am in Pennsylvania btw