InterNACHI Septic flashcards
InterNACHI Septic · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Septic tank
- A watertight buried vessel that receives building sewage, retains solids and scum, and discharges partially clarified effluent to the absorption area.
- Scum layer
- The floating layer of fats, oils, grease, and light solids at the tank surface; the outlet baffle is designed to draw below it.
- Sludge layer
- The settled solids at the tank bottom that must be removed by pumping; accumulated sludge is the main reason tanks need periodic pump-outs.
- Outlet baffle
- A tee or baffle at the tank outlet that draws effluent from the clear middle zone and blocks scum and floating solids from leaving the tank.
- Distribution box
- A level box after the tank that splits effluent among drainfield laterals; its outlets must be at equal elevation for even distribution.
- Percolation test
- A field test measuring how fast water drops in a soil test hole, expressed in minutes per inch, used to size the absorption area.
- Soil loading rate
- The volume of effluent applied per unit area of trench bottom per day (gpd/ft²); finer, slower soils require a lower rate and larger field.
- Limiting condition
- A layer such as bedrock, high groundwater, or a fragipan that restricts effluent treatment; required vertical separation above it governs site suitability.
- Vertical separation
- The depth of unsaturated soil between the trench bottom and a limiting layer, needed so effluent is treated before reaching groundwater.
- Sizing formula
- Absorption area equals daily design flow divided by the soil loading rate; design flow is often estimated from bedroom count.
- Drainfield laterals
- Perforated pipes in gravel or chambers that distribute effluent into the soil for absorption and treatment; they must be level within each trench.
- Confined space
- A tank interior with limited entry and hazardous atmosphere (hydrogen sulfide, methane, low oxygen); entry requires monitoring and is not part of a visual inspection.
- Inspection sequence
- Review records, check fixtures for slow flow, locate and open the tank, then inspect the D-box and drainfield surface for effluent.
- Effluent level check
- Measuring the liquid level against the outlet invert; at or above the invert indicates the drainfield is not accepting flow.
- Report limitations
- A statement of what was not examined, such as buried laterals or an unopened tank, so the client knows the inspection's scope.
- Surface inspection
- Evaluating the drainfield from the surface for ponded effluent, odor, and vegetation patterns; probing is limited and must be described.
- Pumping interval
- Typically every three to five years, adjusted for tank size and occupancy; the reliable trigger is measured scum and sludge depth.
- Pump-out criterion
- A common rule is to pump when combined scum and sludge reach roughly 25 to 30 percent of the tank's liquid depth.
- Flushable wipes
- Products labeled flushable that do not break down in a septic tank; they accumulate as solids and can mat in the drainfield.
- Hydraulic load
- The daily volume of wastewater entering the system; leaks, laundry surges, and clear-water connections raise it and can overload the drainfield.
- Drainfield protection
- Keeping vehicles, structures, and deep-rooted plants off the absorption area and diverting roof and surface water away from it.
- Septic additives
- Products marketed to reduce pumping; biological additives do not remove accumulated solids and some can harm the tank's biological balance.
- Surfacing effluent
- Ponded or odorous wastewater appearing at the ground surface over the drainfield, the classic indicator of hydraulic failure.
- Slow drains
- Fixtures draining slowly throughout the house with gurgling suggest a full tank, a blocked line, or a saturated absorption area.
- Solids carryover
- Sludge or scum escaping the tank, often through a missing or broken baffle, that clogs the drainfield and causes premature failure.
- Root intrusion
- Tree and shrub roots entering laterals or the tank through joints and cracks, blocking flow and damaging the absorption area.
- Settled D-box
- A distribution box that has gone out of level, causing effluent to flow to one lateral and overload part of the drainfield.
- Drainfield restoration
- Options such as resting the field, aeration, or replacement; pumping alone does not restore the soil's ability to accept effluent.
- Hydraulic overload
- Excess water entering the system beyond the drainfield's capacity, the most common cause of premature absorption-area failure.
- Aerobic treatment unit
- A tank that adds aeration and aerobic bacteria to treat effluent to a higher standard before dispersal, requiring more frequent servicing.
- Building sewer
- The pipe from the house to the septic tank, typically sloped about one-quarter inch per foot so solids do not separate.
- Setback distance
- The locally regulated minimum separation between a septic component and a well, surface water, property line, or foundation.