Even though a septic system is usually inspected by the county or city Total Care Property Inspections recommends that you have a independent inspector also. A "septic system," also referred to as a private, on-site waste disposal system, receives waste water and solids from a building's plumbing facilities (bathrooms, kitchens, shower, laundry), treats, and then disposes of the effluent from this waste, by permitting it to absorb into soils at the property.
Septic effluent treatment is accomplished by bacterial action in the "septic" or "treatment" tank and it is mostly accomplished by bacteria in the soil around and below the effluent absorption system, or "drain field." This bacterial action is needed to reduce the level of pathogens in the effluent discharges from the waste system into the soil. The principal components of a private on-site waste disposal system usually include the following:
- piping connecting the building to the treatment tank
- a septic or treatment tank which retains solid waste
- piping connecting and conducting clarified effluent from the treatment tank to a distribution box
- a distribution box connecting the effluent line from the tank to the absorption system or "drain field"
- an absorption system which permits effluent to drain to soils below
- a bio-mat or bio-mass of pathogen-digesting bacteria which forms in soil below the absorption system.
Many variations on this general scheme are used, depending on local climate, soil conditions, available space, economy, and available materials. Special equipment and systems may be designed for problem or difficult sites such as rocky or wet ground, permafrost, or wet tropical marshlands.
INSPECTION AUTHORITY: some municipalities and states provide septic inspection and testing certification. However a generalist inspector, in the course of a home inspection, is permitted to observe and report visual evidence of defects, probable, or possible defects, just as any contractor might observe and report when coming to a property for any reason. This can be completed with dye tablets.
For municipalities requiring certification of septic test providers, home buyers,sellers and agents should consult with local officials for further advice.
Inspecting Outside Waste Piping
Outside waste piping conducts sewage (black water and gray water) from the building to the treatment tank or "septic tank," and from the treatment tank to the distribution box. These lines should be of solid, non-perforated material and need to be protected from mechanical damage (such as by vehicles). Piping extending from the distribution box into drain fields is normally perforated, though solid lines might be used if effluent is being processed by more specialized devices such as seepage pits, galleys, or a sand-bed system.
House to tank
This line may become blocked by waste, damaged by collapse of a section, or invaded by roots. Detection of these conditions is fairly easy by routing a snake or power snake from the building drain to the septic tank. An experienced power snake operator can often tell by "feel" that a drain line is collapsed, partially collapsed, or invaded by roots. While you may make a temporary "repair" of such a condition by drain-cleaning, if the line is broken or root-invaded, you should expect to have to excavate and replace it soon.
Tank to Distribution Box
The same failures can occur on this line as from house to tank. Opening the D-box can also show whether or not effluent is being directed uniformly into each of the leach lines. A tipped D-box can overload one line and cause early failure of the absorption system. If this is happening, flow adjustment end-caps (eccentric holes) can be installed in the distribution box on the inlet end of each of the drain lines, permitting adjustment of effluent delivery into each line, perhaps relieving the problem line and redistributing effluent into the others.
Drain field piping
In a conventional "drain field" of perforated pipes buried in gravel-filled trenches, a drain line may be invaded by tree roots. This is why experts advise keeping tree and shrub plantings away from drain fields. Vehicle traffic can also collapse this or any outdoor waste piping, which is why experts advise against ever driving over a drainfield or over any other septic system components.
Inspecting Septic Tank Condition
The purpose of the treatment tank or "septic tank" is to contain solid waste and to permit the beginning of bacterial action to process sewage into a combination of clarified effluent, settled sludge, or floating scum in the tank. An intact, un-damaged septic tank is normally always filled with these materials. However the inspector performing a "visual" check of the septic system needs to be alert for some important findings:
- Subsidence at the tank location - may risk dangerous, potentially fatal collapse
- Evidence of backup or effluent breakout at the surface in the tank area
Only by pumping and visual inspection can actual tank capacity and condition be completely determined. Probing in the area of a tank, without excavation, is not recommended as the probe may damage a steel or fiberglass tank. When a tank is uncovered for pumping additional critical details may be observed before the pumping operation.