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Inspecting &Testing the Septic System Distribution Box InspectAPedia®  -     How to find the septic drainfield D-box - septic distribution box How to inspect the septic system distribution box for clues of septic drainfield condition Simple repairs at the D-Box can improve septic drainfield performance and may eliminate septic odors

Here we discuss procedures for locating and inspecting the septic drainfield distribution box, or the "D-box". This series of articles discusses Inspection and Reporting the Condition of Private Residential Waste Disposal Systems - or - Where Does it Go When I Flush? and ... Will We Meet Again?

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INSPECTING THE D-BOX - Inspecting the Septic System Distribution Box

The distribution box (more than one may be in use) connects a single effluent line from the septic tank to a network of absorption system components such as drainfield leach lines or to a network of seepage pits or galleys.

The photo (left) shows the adjustable weir outlets that permit balancing flow among drainfield lines. (Source EPA who used photo from Ayres Associates.) More sketches of D-box layouts and configurations are shown in this EPA drawing.

Regulating effluent distribution: In good system design the outlet openings from the distribution box to each drainfield line can be adjusted to regulate the flow among the various absorption lines.

Elegantly simple, a plug with an eccentric hole is inserted into the end of each leach line fed from the D-box. By turning the plug in the end of the leach line pipe one can place the eccentric hole higher or lower with respect to the bottom of the distribution box, thus compensating for a slightly tipped box, differences in leach line length, or differences in leach line condition.

Uneven effluent distribution: If a distribution box becomes tipped (or clogged) effluent may be routed to only a portion of the absorption system, thus overloading it and leading to a "breakout" of effluent at the surface or to clogging and system backup.

An examination of the septic system distribution box interior may show flood lines in the box if the drain field has been clogged or saturated in the past even if at the time of inspection the box is not flooded.

If the septic drainfields have been flooded you should be pessimistic about the remaining life of the absorption system.

If the septic drainfield distribution box is tipped and/or septic system effluent arriving from the septic tank has not been uniformly distributed among the drainfield lines (assuming they are of equal length and in equally good soils), only a simple adjustment of the outflow may be needed.

Round plugs with eccentric openings may be present or can be inserted in the D-box outlet openings to regulate flow among the individual absorption lines. (C)Trap Daniel Friedman Copyright Protected text. Also see ALTERNATING BED SEPTIC SYSTEMS.

Tipped or flooded distribution boxes, resulting in uneven loading of soil absorption system lines. This condition can flood one or two lines leading to early field failure.

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SEPTIC DRAINFIELD INSPECTION & TEST
  SEPTIC D-BOX INSPECTION
  SEPTIC DYE TESTS
  SEPTIC FAILURE SPOTS
  SEPTIC FIELD FAILURE CAUSES
  DISPOSAL CLOGGING FAILURES
  DISPOSAL vs TREATMENT
  SEPTIC DRAINFIELD LIFE
  SEPTIC FAILURE CRITERIA
  SOIL CONDITIONS
  PLANTS OVER SEPTICS
  SEPTIC FAILURE LAWSUIT
  SEPTIC INSPECTION WORK SHEETS
SEPTIC SYSTEM FAILURE CAUSES
SEPTIC TANK INSPECTION PROCEDURE
SEPTIC SYSTEM DEFINITIONS

Readers of this page should also see System Design Regulations 75-A.7 Distribution lines, distribution boxes, gravity flow, pressure distribution, dosing, siphons design specifications for septic systems.

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• The Septic System Information Website - Extensive, Detailed Consumer and Industry Information on Septic System Inspection, Testing, Maintenance, Alternatives for on-site waste disposal

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