What is the Life Expectancy of a Septic Drainfield ?

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This article explains how we determine the Life Expectancy of a Septic Drainfield ?

How long should a leachfield last? - among the types of septic system failure in the drain field, leach field, seepage bed, or similar component. 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"?

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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Septic System DRAINFIELD LIFE Expectancy - What destroys or shortens the life of the absorption system?

Typical drainfield trench cross section USDA - DJFWe have seen drain fields still working fine after 25 years and others which failed in the first week of occupancy of a new home. In a properly designed septic absorption field the level of usage of the system, site characteristics such as slope, rock, groundwater level, and soil percolation rate have all been considered.

Barring foul ups such as we discuss in this document, such a field may last from 10 to 20 years. USDA sources assert that a properly operated and maintained ST/SAS (septic tank / soil absorption system) should last at least 20 years.

But it's easy to ruin or shorten the life of a drainfield/leaching bed. In fact the same USDA source states that

Studies reported at an Environmental Protection Agency seminar, Orlando FL, November 1979, show that over half [ST/SAS] fail prematurely due to improper operation or lack of adequate maintenance.

Generally, these failures occur when the soil-absorption system [drainfield] becomes clogged.

Preventable clogging, due to a buildup of solids in the [septic] system, is usually extensive enough to require expensive reconstruction of the system. Failures can also cause nearby ground areas, streams, lakes, and water supply systems to become contaminated.

This exposed the public [and USDA, EPA, NPS, FPS, and other government employees] to health threats such as hepatitis, typhoid, diarrhea, and dysentery.

... [ in contrast] The unpreventable failure of the soil-absorption system eventually occurs when growth of the organic material in the wastewater [the biomat (SEPTIC BIOMATS) that forms under and along the sides of a drainfield trench] becomes so large [thick] that they plug up the soil.

Similar studies of advanced wastewater treatment systems such as aerobic systems, sand beds, mound systems similarly found that improper or inadequate operation and maintenance were the primary causes of premature failure of those systems as well.

Notice that our sketch at above left specifies 2-4 feet clearance between the bottom of the drainfield trench and the seasonal high water table. Code requirements on this distance vary, but the point is that even if septic effluent appears to be successfully disposed-of, it may not be adequately treated if the drainfield is not constructed properly. Image (above left) courtesy USDA.

For a better view of the probable life of a specific drainfield at a specific property you'd want to know the

Also see CLOGGED DRAIN DIAGNOSIS & REPAIR where we include in table form:



And to repair drain clogs, see BLOCKED DRAIN REPAIR METHODS.

To understand why a drainfield or soakaway bed ultimately clogs up and stops working also



Continue reading at SEPTIC DRAINFIELD INSPECTION & TEST or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEPTIC DRAINFIELD LIFE FAQs - questions and answers posted originall

Or see these

Articles about the life expectancy of a septic system

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Publisher - Daniel Friedman