Blue babies
I'm glad your grandparents had such good luck with their septic system.
Around here, where the sewers were slower coming and the farms are smaller, we had problems. My obstetrician, who worked with mostly rural people, had several blue babies a year because of septic fields that bled into the wellwater.
Increased regulation, followed by sewer lines paid for by public money, treated that problem, though not soon enough for the little blue canaries in the coal mine.
Government: the big bad preventer of poisoned drinking water.
There really are things that the government ought to be doing.