Septic Tank Inspection and System Evaluation

Septic Inspection
Inspecting a home or commercial septic system means finding evidence that the onsite wastewater disposal and treatment system is working properly. The procedures used must cope with the difficulty that a septic system consists of buried components, involves major costs to replace, and may involve serious health and life safety risks as well.

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.

Wastewater or septic effluent treatment is accomplished by bacterial (and other microorganism) 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. In addition to reducing the level of pathogens and the reduction of organic waste to a combination of new cell masses, CO2, and water, wastewater treatment removes organic matter, nitrites and nitrates, and phosphorous. In an absorption field the soil performs an additional role of filtering the septic effluent.

Advantage Inspection is a state certified septic inspector. We provide this service to our clients for a charge of $245.00. This fee doe not include pumping if necessary for the inspection.

Inspecting the Septic Tank and Septic Tank Area Before Opening the Septic Tank

•Subsidence (depressions or low areas in the soil) at the septic tank location – may risk dangerous, potentially fatal collapse
•Evidence of recent work which may need to be investigated to understand the condition of the septic system
•Evidence of backup or effluent breakout at the surface in the septic tank area
Inspecting the Septic Tank After Opening the Septic Tank but Before Pumping

After Opening But Before Pumping the Septic Tank: When the septic tank is opened before it has been pumped out or cleaned, important information about the condition of the septic system is available:

•Thickness of scum and sludge levels: Septic tank maximum scum and sludge buildup prior to pump out, and instructions for measuring the floating scum layer thickness and settled sludge layer thickness in a septic tank.
•Back-flow of effluent into the tank during pumpdown – an indicator of flooded leach fields
•Condition of the Septic Tank Baffles: damage to the tank baffles. Evidence of a broken concrete septic tank baffle is shown below at our discussion of home made site built tanks, and a rusted-steel septic tank baffle is shown in other photographs on this page.
•Liquid and waste level in the tank: evidence of waste passing over the baffles – a flooded system, an indicator of septic system failure. Evidence of sewage flowing over the septic tank baffle is shown in a photo below where we discuss septic tank baffles.
•Unusually high levels of sewage in the septic tank – suggesting a blocked outlet or drainfield. The drainfield may be failing due a damaged or clogged pipe, a clogged, failing drainfield, or due to groundwater leaks into the septic tank or groundwater that saturates the drainfield.
•Unusually low levels of sewage in the septic tank – suggesting that the tank has a leak, can have several causes depending on the tank age and the material from which it was built.
•Low Sewage Levels in Concrete septic tanks: If the tank is made of concrete it should be pumped and cleaned thoroughly so that your contractor can inspect the tank for cracks or other damage.
•Low Sewage Levels in Plastic/Fiberglass septic tanks: after pumping the tank, look for a lost drain plug in the tank bottom. Even pumping the tank can accidentally remove this plug – a condition you won’t notice until the next time it’s pumped.
•Low Sewage Levels in Steel Septic Tanks: Pump the tank completely, clean and inspect for rust holes – it’s common for the bottom of such tanks to rust completely away.
•Low Sewage Levels in Home Made or Site Built Septic Tanks: there is risk of tank collapse or leaks when septic tanks are site-built such as using concrete blocks or stone. Leaks are likely
Septic Tank Inspection After the Septic Tank has Been Pumped Out

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 begins

SAFETY WARNING: Do not enter or lean down over or into any septic tank unless you’re wearing special breathing apparatus and have a second worker watching you for safety – methane gas in the tank can cause fatal asphyxiation.

It should never be necessary to enter a septic tank. Any work to replace the baffles or repair the tank should be done from the outside.

SEPTIC TANK SOLIDS & SCUM – thickness, net free area, effluent retention time

Solids entering a septic tank are intended to remain there until pumped out during tank service. A large portion of solids settle to the bottom of the tank as sludge.

Grease and floating scum remain at the top of the sewage in the tank. Baffles (discussed above) help keep solids, scum, and grease in the tank. Bacterial action in the tank make a modest reduction in the solids volume and begin the processing of sewage pathogens, a step later completed by soil bacteria in the absorption fields.

Net free area: If the sludge level becomes too high or the floating scum layer too thick, in addition to risking passage of solids out of the tank (damaging the absorption system), the remaining “net free area” of liquid in the tank is reduced. When the net free area becomes too small, there is insufficient time for waste entering the tank to settle out as bottom sludge or top floating scum. The time allowed for sewage to separate and settle out as sludge or collect as floating scum is called septic tank retention time.

For an in-use septic tank with a small net free area, and therefore a short septic effluent retention time, the frequent entry of solid and liquid waste will keep the tank debris agitated, thus forcing floating debris into the absorption system where the life of that component will be reduced (due to soil clogging).

The importance of keeping an adequate net free area in a septic tank is the reason that tanks need to be pumped at regular intervals. Building owners who never pump a tank until it is clogged have already damaged the absorption system and reduced its future life expectancy.