Septic Field Failure: Signs and Types

Septic field failure is the most expensive and difficult problem that can occur with a system.

This post talks about the signs and causes of failure. If you’re looking for alternative solutions, please visit this post: drain field restoration.


  • Bad smell in yard: If you know where your field is, then you can walk to the spot; otherwise, you’ll probably be able to follow your nose. Try to find the source of the smell. If the ground is squishy at the source of the smell, then you almost certainly have a field issue.
  • Similarly, if you find standing water or squishy soil in the yard and it hasn’t just rained, then you may have a serious issue.
  • Extra green grass in one part of the yard can also be a sign that excess water and nutrients are not being absorbed.
  • Finally, if your toilet or drains are sluggish on a regular basis, then the field might be losing its absorbing ability and close to failure.

It’s important to keep in mind that failure is a process not a sudden event. Depending on how often you walk around the yard, you should be able to see warning signs; however, the warning signs need to be taken with a grain of salt. For example, heavy rain fall can temporarily overload the system leading to a smell in the yard, but it should pass fairly quickly. In addition, your drains can be sluggish for a variety of reasons, but if they’re increasingly sluggish on a regular basis, then it might indicate a looming failure.

Three Main Types

  1. Mechanical: This is the least common type of failure and the easiest to fix. Mechanical failure might refer to a truck driving across your yard and crushing half of the distribution pipes or collapsing the columns. In any of these cases, your contractor will simply need to fix the broken component, and it should start working again.
  2. Physical: This refers to a physical clogging of the soil. Washing machine lint is the number 1 offender, but not pumping the tank regularly and/or damage to your its bacteria colony can also lead to small solids traveling into the field. This type of clogging can sometimes by water jetting, or using pressurized water to force clogging material out of the distribution pipes; however, too many solids can cause the actual soil to become clogged leading to poor absorption and eventual biological failure.
  3. Drainfield Failure Pic

    Overgrown Biomat

    Biological: This refers to an imbalance in the biomat (biofilm) that forms along the bottom and sides of the distribution columns; it’s is a slimy, black layer of anaerobic bacteria that help purify effluent. Since the biomat is less permeable for water, the effluent pools on top of it and slowly seeps into the ground. Under ideal conditions, it reaches a state of equilibrium where it’s sufficient to purify water but not so thick that it causes effluent to overflow. The biomat grows out of control when a septic tank isn’t pumped often enough and too much organic material reaches the drainfield. Biological failure can be very difficult to fix and require a brand new drainfield to be installed.

Tips for Avoiding Field Failure

Avoiding Field Failure


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