This article is our home page for identifying, diagnosing & repairing various types of septic system failure in the drain field, leach field, seepage bed, or similar
component.
Beginning here and in more detail in specific articles that we'll recommend, we list the causes of each type of septic component failure, and list the septic component failure criteria
or in other words what conditions are defined as "failure"?
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Absorption Field Failure Causes of drainfields and leaching beds
[Click to enlarge any image]
Is there a Septic Failure or Just a Blocked or Broken Pipe?
How can you distinguish between a blocked pipe, a septic tank that
needs pumping, and a clogged drainfield that needs replacement?
This is an important question as it distinguishes between relatively
low cost maintenance or repair task and a costly septic leach field replacement.
If the septic tank wastewater is above the bottom of the septic tank outlet
pipe then the level in the tank is abnormal and too high.
If at the same time the effluent in the D-box or distribution box is normal,
then probably there is a break, blockage, or damage to the effluent line between the septic tank and the D-box.
If at the same time the D-box is flooded,
then there is either a blockage between the D-box and the actual drainfield trenches and pipelines, OR the septic drainfield is flooded and in failure.
If there is septic effluent at the ground surface
in the area of the drainfield or soil absorption system, then the drainfield is in failure
We summarize causes and failure clues just below and at the page end Recommended Articles list you'll find detailed diagnosis and repair articles for each of these conditions.
Summary of Causes of soakaway bed or disposal field failures:
Soil clogging at the biomat layer
which forms below and around the drainfield trenches (or other absorption systems).
This soil clogging is normal and will occur naturally during the life of any septic drainfield or soil absorption system.
The biomat is a bacteria layer which forms in soil below and around drainfield trenches where septic effluent or wastewater
is discharged.
This layer is critical in the processing of fine biological solids and pathogens which are in the effluent, and
without it the septic system would not be adequately treating the effluent.
Inadequately treated effluent released into the ground
risks contamination of nearby ponds, wells, streams, etc.
But
Watch out: a principal cause of early septic drainfield failure is inadequate maintenance: failing to clean or pump the septic tank at regular intervals.
the absorption system with surface or roof runoff, or rocky, poorly drained or undersized sites may simply lack capacity.
Use of septic tank or drain field additives
which claim to extend system life can, for some of these products such as yeast, actually generate so much activity in the tank that
solids are held in suspension and forced into the soil absorption system!
Do
not add any treatments, chemicals, yeast, or other treats to a septic system. In general these treatments are not necessary for conventional septic systems, don't work, may ruin the system, and
are illegal in many localities.
especially on rocky, poorly drained sites (pipes settle, for example).
Houses clustered around a lake
often will have a marginal system as properties were crowded
together, built as part-time summer camps, were built without code supervision, and often were built using amateur, marginal home-made systems.
Age
eventually even a well maintained SAS will clog and have to be replaced.
Septic System Soil Absorption System Failure Criteria
Expert sources and often building or sanitary codes in most jurisdictions provide a formal definition of what constitutes a septic system failure.
The septic failure criteria listed just below are intended to help avoid unnecessary argument about the condition of a septic system: your local health department may use these indicators to conclude that septic system repair is required to protect public health.
You will see that some of these septic "failure" definitions refer to an improper location of the septic effluent disposal system regardless of whether or not there is actual evidence of a sewage backup in the building or septic effluent break-out inside the building.
Breakout of septic effluent observed at the ground surface (& I consider odors as well)
Septic close to surface water supply
Board of Health (BOH) evaluation in Massachusetts (MA) and some other states or provinces, if a septic disposal field is found to be located anywhere within 100 ft of surface water supply
Sewage effluent disposal found to be located within Zone 1 of a public well
Sewage effluent disposal located within 50ft of a private well
Sewage effluent disposal located between 50ft and 100ft of a private well if well fails bacteria test.
Other Possible Indicators of Drainfield Failure
Some of these septic failure indicators are listed as "possible" because the symptoms we list might be caused by an absorption system failure (clogged, flooded, etc.) OR the same symptoms can appear if an effluent pipe is broken or blocked between the building and the septic tank, or between septic tank and the drainfield.
Sewage backup into the building
Wastewater level in the septic tank above the bottom of the septic tank outlet pipe
Wastewater effluent level in the Distribution box or D-box that is above the D-box outlets to one or more drainfield pipelines
Wastewater effluent found backing up to the starting end of a septic drainfield trench or drainfield pipe
Construction of a septic drainfield in an area subject to area flooding
Septic system improperly constructed by any health department standard.
For example and illustrated above on this page, if the bottom of a the septic mound or raised bed septic system trench is less than two feet above the seasonal high water table then the system cannot reliably treat septic effluent year round and the system is considered improperly-built and thus "failed".
Plants, especially deep-rooting plants or trees, over the septic drainfield or soakaway bed are likely to spell the end of the septic system soil absorption system even if it still seems to be working - the septic drainfield forward life is not predictable.
SOIL PERCOLATION TEST MANUAL, CNMI Division of Environmental Quality, Gualo Rai, Saipan provides an excellent English Language manual guide for soil percolation testing. Original source: www.deq.gov.mp/artdoc/Sec6art108ID255.pdf
SOIL TEST PIT PREPARATION, fact sheet, Oregon DEQ Department of Environmental Quality, original source www.deq.state.or.us/wq/pubs/factsheets/onsite/testpitprep.pdf The Oregon DEQ onsite water quality program can be contacted at 811 South Ave, Portland OR 97204, 800-452-4011 or see oregon.gov/DEQ/
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Citations & References
In addition to any citations in the article above, a full list is available on request.
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.