A septic dye breakout over a septic leach field indicates field failure in this case - an expert can find clues and perform tests that reduce risk of a costly surprise Home Buyer's & Seller's Guide to Septic Drainfield Failures
     


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Septic drainfield failure detection & actions when buying a home: this article series discusses how to diagnose and repair Septic Drain Field Failures. We describe common causes of leachfield failures, and we give advice for home buyers or home sellers for the case when a septic failure is discovered during the home sale process.

This article series outlines what goes wrong with septic systems and their various components and describes septic inspection and test methods in detail, explains how to be sure your septic inspection and septic test are conducted properly, tells you where to get more septic system information about a given property, and warns of unsanitary or dangerous site conditions.

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Drainfield or Soakaway Bed Failures: Septic Leach Field Failures that Occur When Buying or Selling a Home

Some septic system repairs are comparatively modest, such as replacing covers or baffles. Replacing septic tanks or leach fields is costly. No leach field has an infinite life, but proper septic system maintenance can defer this cost. Because costly septic system repairs may be upcoming, buyers of properties with a septic system are advised to inspect and test the system before purchase.

Clogged drainfield soils

sketch of cross section of a drainfield trench
The most common and normal drainfield end-of-life failure is clogging of the soils around the drainfield trench.

As we elaborate below, with time and age and normal drainfield functioning, a natural formation of a biomat around the drainfield trench ultimately leads to a thick slime layer that blocks wastewater passage into the surrounding soils.

But failure to pump the septic tank on schedule allows suspended solids and greases to flow into the drainfield, speeding up this clog-up process. Pumping the septic tank on proper schedule (SEPTIC TANK PUMPING SCHEDULE) and use of a septic filter (FILTERS SEPTIC & GREYWATER) are two steps that most add life to a conventional septic tank and drainfield design.

The sketch shows a conventional drainfield trench in cross section. As the drainfield line ages the soils become clogged around the distribution piping, starting first at the end closest to the septic tank or distribution box.

Eventually soils around the entire line are clogged with a thick biomat, or perhaps worse, by grease or salts that should have stayed in the septic tank. At this point the soil absorption system stops absorbing effluent. The soils around the leaching bed trenches have become clogged and stop passing effluent. Sending grease and floating solids into the leach field hastens this failure.

The biomat which forms below and around the sides the leaching beds will eventually also become too solid and impacted, stopping soil absorption. In this leach field photo effluent was appearing in the light colored area where the homeowner had begun some exploratory digging in a soggy spot only to see her hole fill up rapidly with effluent.

In the building drains become sluggish, stop, or back up into the building (unsanitary), or effluent may appear on the property surface when the absorption system can no longer function or where a pipe has become damaged.

Flooded Drainfield Soils

LARGER VIEW of this
costly surprise caused by building a swimming pool over the drainfieldA septic drainfield that has become saturated for any reason is no longer functional. Saturated leachfield or soakaway bed soils mean that the wastewater effluent is not being treated by bacterial action and that unsanitary wastewater is being discharged into the environment.

Our photo (left) shows several drainfield failure troubles: flooding over the drainfield and a nearby lake.

Depending on soil conditions, land slope and shape, and perhaps other conditions, a saturated drainfield may not be immediately apparent, but this failure shows up in the following ways:

  • Septic wastewater breaks out or appears at the ground surface on or near the drainfield during normal use of the system at any time, seasonally in wet weather or always or at irregular intervals
  • Septic wastewater breaks out or appears at the ground surface on or near the drainfield during a properly-conducted septic loading and dye test
  • Inspection reveals flooding in the D-box
  • Inspection during septic tank pumpout reveals sewage wastewater flowing backwards from the drainfield into the septic tank
  • Sewage odors in or around the drainfield area or possibly at the septic tank or D-box
  • Abnormally high sewage levels in the septic tank, flooding over the tank baffles
  • Sewage backup into the building or slow building drains
  • See SEPTIC DRAINFIELD FAILURE DIAGNOSIS for details.

Building on or over or too close to the leach field causes failures

LARGER VIEW of this
costly surprise caused by building a swimming pool over the drainfiel CLASS= A leach field can be destroyed by other site "improvements" such as this attempt to install a swimming pool atop the leaching area in the photo shown at left.

This mistaken installation involved multiple errors: placing a pool atop the leaching area which prevents proper oxygenation and evaporation, driving over the leach field which risks damaging buried pipes and compacting the soil, and excavating to remove a portion of the absorption system soil to put in the swimming pool.

  • Gray wastewater (laundry detergent) has appeared at the ground surface by an aboveground swimming pool
  • A fool constructed the swimming pool right over part of the septic drainfield - driving equipment over the trenches (compacting soils or breaking piping), removed soil cover, and installed a pool over part of the drainfield surface, interfering with wastewater transpiration or evaporation. More on the mistake of building over the drainfield is provided below

    The gray water you see next to the swimming pool in this larger photo was effluent from the failed septic fields.

Compacted Soil Drainfield Failures

Photo of parking lot
atop a possible drainfield location - likely to ruin the field by compacting the soils.  septic dye breakout shows a total septic system failure at a parking lot

Compacted soils due to parking or driving on the septic drainfield: driving over the leach field in any vehicle larger than a child's bicycle is a bad idea. Heavy vehicles may actually crush buried leach field lines, or they may compress the soils around the leach field, either of which leads to failure.

Driving on or parking on leach fields will destroy them.

This property actually had no working septic system at all - 100% of its effluent was coming to the surface nearby, brought out by solid rock covered with shallow soils, and running down a steep hill into a local stream.

Paving over the leach field means not functional


A leach field cannot function properly if it is paved-over. Some folks may try this as a way to permit parking over the absorption system.

But paving prevents both evaporation of effluent (a portion of the effluent disposal method) and it prevents oxygen from reaching the soil, thus inhibiting proper bacterial action needed to treat the effluent.

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