For more than 20 years, pumpers and installers have popped the lids on precast tanks to occasionally find eroded outlet baffles, a flaky white substance engulfing exposed concrete aggregate and deteriorating and collapsing walls. Distribution or drop boxes crumbled when touched. Now experts are working to unravel the mystery of why this deterioration doesn’t affect every tank, and when it does attack, doesn’t always follow the same patterns. Hydrosulphuric acid, a naturally occurring byproduct of the thiobacillus bacteria in septic tanks, was deemed the clear culprit. Though until recently, no one questioned if extenuating circumstances were accelerating the deterioration process.In
