There is an environmental downside to septics too. Where I grew up there was a sandy aquifer that caused nitrogen loading from septic run off in ponds and marsh

There is an environmental downside to septics too. Where I grew up there was a sandy aquifer that caused nitrogen loading from septic run off in ponds and marshes. This attributed to algea growth, oxygen depletion and marine species die-off. There is now an extensive effort to sewer the region.