Defects, Failure Indicators, and Remediation
What this domain tests
Defect questions ask you to distinguish a maintenance issue from a failing component and to recommend proportionate remediation.
Core rules and concepts
- Failure indicators include sewage backup, slow fixtures, outdoor odors, surfacing effluent, unusually lush grass over lines, standing water, and pump alarms.
- Common causes: solids carryover from a missing or broken baffle, a full tank, biomat clogging, hydraulic overload from stormwater or high water use, root intrusion, crushed pipe, a misleveled distribution box, and pump or float failure.
- Diagnose before prescribing. Check tank levels, baffles, filter, distribution box, and pump before concluding the field has failed.
- Remediation ranges from pumping and baffle repair to jetting laterals, replacing a distribution box, installing a new field, adding a mound or advanced treatment unit, or connecting to a sewer.
- A failed field cannot be restored by pumping alone if biomat has sealed the infiltrative surface.
Worked example
Effluent ponds over one section of a drainfield after heavy rain, but the tank level is normal at the outlet. The likely cause is saturated soil or localized biomat, not a full tank. The reasoning: a full tank would show a high level at the outlet; a normal level with surfacing effluent points downstream. Recommend reducing water use, diverting runoff, and evaluating that section before replacing the entire field.
Traps that cost marks
Do not label every odor a failed field; a dry trap or roof vent issue can cause it. Do not recommend field replacement before checking the distribution box and laterals. Do not ignore stormwater. Do not confuse a pump alarm with a treatment failure.