Septic Processes & Problems
Hydraulic Failure
Hydraulic failure occurs when more water enters a septic system than it can process and absorb. The drainfield has a finite absorption capacity determined by soil type and trench footage — when water inputs (toilet flushes, showers, laundry, dishwasher cycles) exceed that capacity over a sustained period, the soil becomes saturated and effluent has nowhere to go. It backs up into the tank, into the house plumbing, or surfaces on the ground above the drainfield.
Hydraulic failure is distinct from biological failure (biomat blockage) though they often occur together. Common causes of hydraulic overload include large gatherings, excessive laundry use, leaking toilets or fixtures running continuously, directing roof drains or sump pumps to the system, and high water table conditions that reduce soil absorption capacity seasonally.
What This Means for You
To reduce hydraulic stress on your system: repair any leaking toilets or fixtures immediately (a running toilet adds 200+ gallons per day to your septic system), spread laundry use across the week rather than doing all loads on one day, and never direct roof drains, gutters, or sump pumps toward the drainfield area. During spring snowmelt, when the water table rises, minimize water use to give your system recovery time.
Related Terms
Drain Field Saturation · Drain Field (Leach Field) · Septic Failure · Septic Tank