Failed septic systems

What causes septic systems to fail?

There are many causes of septic system failure.  Poor installation, improper maintenance, tree roots, hydraulic overload (using too much water!,) high-strength waste (restaurants for example,) seasonal groundwater table, physical damage, etc…Proper failure investigations determine the most likely cause of the failure, which determines the best option for repairing the system. 

One of the most common causes of failure is sometimes referred to as the “creeping crud” or “old-age” or Biomat failure.  Several factors contribute to the development of the biomat; time, wastewater strength, hydraulic load, groundwater saturation, and maintenance are the major ones. 

The pictures below show the progression of the “creeping crud” and how it eventually causes sewage to surface over the drainfield.  The first view shows a newer drainfield line with the effluent moving downward through the soil.  The second shows how the biomat grows along the bottom of the trench, and then slowly up the sidewall.  The third is a progression of growth along the sidewall of the drainfield, and the fourth picture demonstrates total encapsulation of the drainfield causing sewage to surface over the top of the drainfield rather than moving downward through the soil.  

When this happens, you have two choices for fixing the problem... drainfield replacement (digging up your yard!) OR Remediation.

For a more detailed explanation of the science behind Biomat formation and biological functions of the septic system, click here.   

This is what the biomat looks like when using a soil auger to dig down to the top of a failed system.  The black biomat came from the few inches of soil directly on top of the drainfield.

A Few Other Causes of Septic System Failure

A proper investigation is critical in determining the best way to repair a failed septic system.  All too often, a homeowner is misinformed on why their system failed and the best way to repair it.  If the person doing the investigation, usually a contractor or health inspector, does not know how or does not take the time and effort to do it properly, then the wrong diagnosis can be made.  This can be costly to the homeowner!   Proper investigations will determine WHY a system failed and the best way to fix it.  Here are a few photos of problems that can cause your system to fail...

Roots almost completely clogging a distribution box.

Roots blocking flow through a pipe in the system.

A septic tank that had never been pumped... it is full of solids, reducing
treatment time in the tank
, and spilling soil-clogging sludge into the

The owner of this aerobic treatment unit thought they could get by without
a little preventive maintenance.

This is a good example of poor soil and a shallow water table.  The
drainfield won't work if it is saturated with ground water.

Matt Vinson
(478) 457-5292
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