Definitions of Septic System Failure

  • SEPTIC FAILURE CRITERIA - CONTENTS: How do we define septic system failure ? When is a septic system considered "in failure" ?Here is a list of Types of septic system drain field failure. Cause of septic system component failures. Definitions of septic failure for each component
  • POST a QUESTION or READ FAQs about the definition of septic system failure or drainfield failure

Criteria for defining septic system failure: this septic system inspection and test article discusses the Definition of Septic System Failure - septic system failure criteria - 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"?

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Onsite Waste Disposal System Septic System Failure Criteria

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 discuss what can be planted over and near a septic drainfield and what should be avoided.

Massachusetts Title 5 lists specific failure criteria and serves as a good model for septic inspections anywhere.

Septic drainfield cross section sketch
  • Backup anywhere in the system
  • Discharge of effluent to the surface, stream, etc. regardless of whether or not septic dye is observed
  • Static effluent level above outlet in the D-box
  • System has to be pumped more than four times a year
  • Metal septic tanks (municipality dependent; note that in special site conditions small metal tanks may be the "only" solution and may be approved by local officials. An owner/buyer must be informed of the implications of such installations.)
  • Soil Absorption System (or cesspool, etc) is at a depth exposing it to the maximum groundwater level - as shown in our illustration, above-left.

Cesspool failure criteria

  • Less than 6" of freeboard (free area between top of the effluent in the cesspool and top of the cesspool container)
  • Less than 1/2 day's storage
  • Within100 feet of a pond or dug well (surface water supply)
  • Within 50 feet of a private well (modern sanitary well)
  • Between 50 and 100 feet from a private well if well fails bacteria test
  • In Massachusetts, within Zone 1 of a public well
  • BOH (board of health) evaluation is required if septic system components or evidence of failure are within 50 feet of any surface water


Soil Absorption System Failures (leach fields, drain fields, seepage pits)

  • Breakout of effluent observed (& I consider odors as well)
  • BOH evaluation in MA if within 100 ft of surface water supply
  • within Zone 1 of a public well
  • within 50ft of a private well
  • between 50ft and 100ft of a private well if well fails bacteria test.

FAILURE CRITERIA - Soil Absorption System Failure Criteria - Drainfield Failure Standards

Since homeowners may receive vague advice about the condition of their septic system, here we present specific failure criteria for septic systems. For alternative septic system designs or advanced septic systems using more specialized equipment, a failure of that equipment is more often a needed repair than a total system failure.

The most basic definition of septic system failure would be a septic system that will no longer treat and dispose of septic effluent. A "blocked" septic system may or may not be a "failed" system - it depends on the cause of blockage. Is it a blocked pipe, a clogged septic filter, or is the drainfield saturated and no longer accepting effluent?

Here are some of the specific criteria that can reliably be taken to describe a failed or non-functional septic system:

  • Breakout of septic effluent observed at the property surface (& I consider odors as well)
  • Appearance of septic effluent, for example seen by use of a tracer dye, in nearby waterways, streams, lakes, or drainage catch basins
  • Too close to water supply or other boundaries: Board of Health evaluation in Massachusetts defines a septic system as unacceptable (technically not working" if a septic system (or in some cases its drainfield) is located within 100 ft of surface water supply or any of the next three locations:
  • A septic system (or in some cases its drainfield) located within Zone 1 of a public well
  • A septic system (or in some cases its drainfield) located within 50ft of a private well
  • A septic system (or in some cases its drainfield) located between 50ft and 100ft of a private well if well fails bacteria test.

Also see SEPTIC FAILURE SIGNS: what can we see that indicates a septic system is failing, Septic Failure Causes in our septic inspection online book, and see SEPTIC DRAINFIELD LOCATION: how to find the septic drain field or leaching bed.

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