Septic system terminology glossary

Below is a listing of some terms you may find as applicable to septic systems

Abandonment - Removal of a septic tank and leach field such that water does not collect within. Abandonment of septic system components is typically done in conjunction with repair, replacement, or connection to municipal sewer.


Absorption Area - The gravel to soil interface in the dispersal system.

Absorption Field - A broad term for the dispersal after a septic tank.


Absorption Trench - A broad term generally referring to a leach line; this term could signify various types of leach fields.


Access Cover - A manhole sized cover at the ground surface to gain access to the septic tank. Almost always, there are two access covers to residential septic tanks.


Active Venting - Venting septic system components by mechanical means. 


Aerobic Treatment Unit - A general classification for a proprietary treatment unit that adds oxygen to the effluent. These units are intended to allow aerobic bacteria to thrive.


Aggregate - Gravel 


Alarm  - Audible and/or visual to alert the system occupants of a conditions that needs attention.


Alternative OWTS (Alternative Septic System) - A general term for a septic system that uses technology beyond conventional leach lines.


Anaerobic  - An environment without oxygen.


Application Rate - The design rate that effluent is applied to the absorption area.


At-Grade Bed - A type of dispersal field. Dispersal is at or just below the existing ground surface with distribution by a approximately 8 to 12' wide bed rather than narrow trenches.


ATU- Aerobic treatment unit


Baffle - A vertical wall in the septic tank that divides the inlet and outlet compartments.


Basal Area - The absorption area


Biochemical Oxygen Demand - The amount of dissolved oxygen required by the organisms in the effluent.


Biomat - A clogging mat that is developed over time with a dispersal field.


Blackwater - Layman's term for building sewer.


Boulder - A large rock that is sometimes a limiting condition.


Breakout - Surfacing of effluent on the ground surface. Can be caused by many means, but indicates that corrective action is necessary.


Building Sewer - Raw sewage from a building. Different building uses have different strength sewage.


Capacity Of Septic System - The amount of sewage that a septic system can handle. Typically measured as a daily flow.


Centralized Septic System - Type of septic system that combines multiple buildings into one system.


Cesspool - A box in the ground that seeps effluent immediately around the box rather than through a dispersal field.


Chemical Toilets - Portable toilets


Clay - A very small soil particle


Cleanout - Access to the building sewer.


Cluster Septic System - Another term for centralized septic system.


Cobble - A rock smaller than a boulder but larger than gravel.


Coliform - Bacteria, can be used as an indicator for water quality analysis


Commercial - A system use that is not residential in nature, often higher flows or unusual strength.


Contractor - The installer of a septic system.


Control Panel - The connection of floats, pumps, and controls that allow sophisticated means of effluent handling.


Conventional Gravity Septic System  - A traditional treatment train of septic tank to gravity leach lines.


Cover Soil - Soil above the gravel in a leach line. Typically about one foot of soil cover over a typical leach line.


Creek - A watercourse that septic system components must meet appropriate setbacks from.


Curtain Drain - Subsurface drain intended to move subsurface water from an area.


Cut Bank - Removal of soil from terrain such that a change from the natural terrain in made.


Decentralized Wastewater System - A general term for a septic system.


Demand Dose - Activation of a float switch cycles the effluent pump to discharge.


Denitrification - A process reduces nitrate into nitrogen through a series. 


Design - Detailed information of the septic system specifying specific components and locations. 


Design Flow - The amount of sewage anticipated to be served by the septic system.


Deviation - A change from the typical technique. Sometimes for difficult sites there is a need to deviate from the normal process when appropriate.


Discharge Effluent Pipe - The pipe that effluent passes through leaving a septic tank.


Disinfection - Destroy bacteria


Disposal - An old term used to refer to "get rid of" sewage


Dissolved Oxygen - The among of gaseous oxygen in the effluent.


Distribution Box - A small box used to distribute the effluent transport pipe into multiple leach lines.


Distribution Lateral - The perforated pipe running the length of the leach line.


Distribution Valve - A valve that cycles between different leach lines.


Diversion Valve - A valve that is manually cycles to switch between duplicate leach fields.


Dosing Chamber - Another term for pump tank.


Drain Rock - The gravel within the leach lines.


Drainfield - Another term for leach line, but can also be a general term for any type of septic system.


Drinking Water - Water that is contained in usable groundwater aquifers.


Dripfield - A type of dispersal field that uses shallow drip tubing to make use of the shallow soils.


Drop Box - A box used in serial distribution to allow full use of the upper leach line then use of the next leach lines in the series.


Drywell - An outdated term used sometime to refer to a leach field.


Dye Test - A technique that can used to identify surfacing sewage.


Effective Depth - the depth of acceptable soil below the gravel in a leach field.


Effluent - Treated sewage. Can refer to primary level treatment of a level beyond.


Effluent Breakout - Similar to surfacing sewage, but surfacing in the dispersal field rather than before.

effluent filter - A device installed in the septic tank outlet to trap particles that haven't been treated in the septic tank. 


Effluent Pump - Pump that is intended for septic tank effluent applications.


Engineer - The person or firm responsible for the appropriate design of a septic system. Questions should be directed to him rather than the installer.


Existing Ground Surface - The surface prior to installation.


Expansion Area - An area set aside and available for future installation of a leach field once the primary leach field has reach the end of its useful life.


Failure - Could refer to a great number of issues, specific items must be considered in the diagnostics.


Fats, Oils, And Grease - FOG, typically seen in commercial kitchen applications, these float on the surface of a septic tank. Grease interceptors are often added when FOG is anticipated.


Fecal Coliform - Bacteria that originate in the intestines of mammals. Can be an indicator or contamination.


Fifty percent rock - typically a limiting condition for a leach field.


Fill - Soil that is moved from one location and placed in anther.


Filter - A general term for outlet filter.


Filter fabric - non-woven fabric that is placed on top of the gravel in a leach line. Intended to keep solid from entering the leach field gravel.


Float, control - A switch that is used signal a level condition in a pump tank.


Flow Thorough Port - A hole in the septic tank baffle that allows passive venting of the outlet compartment.


Force Main - A general term for a pressure effluent transport pipe or raw sewage transport pipe.


French Drain - Layman's term for curtain drain.


Gravel - Drainrock used in the leach line.


Gray Water - A layman's term for some types of sewage.


Gray Water System - A system used for some types of sewage.


Grease interceptor - A tank with multiple compartments intended to separate FOG from the sewage.


Grinder Pump - A pump that grinds sewage. These should be avoided in septic system applications.


Groundwater - Water contained beneath the ground surface. 


Groundwater Monitoring - Monitoring done throughout a period of time (several months or years) to determine the depth from ground surface to groundwater.


Heavy Equipment - Backhoes, excavators, dump trucks, loaders


High Strength Sewage - Sewage containing a higher level on BOD, TSS, and/or nutrients than typical residential strength sewage.


Holding Tank - A non-self discharge tank. Vacuum truck is required to remove the sewage. Treatment or discharge occurs.


Infiltration - Water that is allowed to enter septic system components from the groundwater or surface water.


Infiltrative Surface - Another term for application area.


Influent - Another term for sewage.

injection well - A term sometimes used by the US EPA to refer to the broad classification of subsurface effluent discharge.


Inlet Tee - An arrangement of pipe where the building sewer enters the septic tank. The inlet tee allows sewage to enter the approximant middle zone in the septic tank.


Installer - The person or firm that installs the system.


Junction Box - A box where electrical connections are made. Ease of service must be considered here.


Leach Field - The dispersal field type consisting of trenches in the ground. Designed based on the site and soil conditions.


Lift Station - A term identifying pumped either sewage or effluent.


Limiting Layer - A condition found subsurface that a leach field bottom must have vertical setback from.


Loam - A fair combination of sand, silt, and clay.


Logic circuit - A device that can be used to efficiently dictate controls and pumping methods.


Maintenance - Service conducted at routine intervals to maximize the value of a septic system.


Maximum Daily Flow - The maximum amount of water use on a daily basis.


Mound  - dispersal field type in which the near surface soils are used for application. Typically used in high groundwater settings.


Nitrate - Nutrient of concern in effluent.


Observation Well - A port to observe the condition of a leach line. 


Onsite Wastewater Treatment System - Another term for septic system


Operating permit - A permit issued in some jurisdictions for use of a septic system.


Outlet Filter - Another term for effluent filter


Outlet Tee - An arrangement of pipe allowing the clear zone of the septic tank to flow to the leach field.


OWTS - Onsite Wastewater Treatment System


Passive Venting - Venting of the septic tank without mechanical assistance.


Perched Groundwater - Groundwater that is high during some seasons, usually connected to the potable aquifer.


Percolation Test - A test used to correspond the percolation rate to a long term soil acceptance rate.


Performance Well - A pipe extending to the bottom of the effective soil to monitor conditions.


Plan - A site layout from a bird's eye view.


Plan Details - Information relating to the plan and providing further details of septic system components.


Pollution - Can be in many forms.


Pressure Distribution - A technique for distribution of effluent to a leach field.


Pretreatment - A term used to identify additional treatment beyond septic tank effluent.


Professional Engineer - An individual licensed to practice civil engineering. 


Proprietary Treatment Unit - An ATU made by a specific manufacture.


Pump Chamber - A tank where the effluent pump is and pulls effluent from to pump.


Pumper - The service provider that evacuates septic tank septage.


Pumper truck - The vacuum truck that a pumper uses.


Raw Sewage - Sewage prior to any treatment


Records - Important documentation that should be kept available for reference.


Regulator - The government agency that regulates septic systems.


Repair - Can be small change or complete replacement.


Reserve Area - Area maintained to be available for future replacement of the leach field.


Residential Strength Sewage - typical household sewage


Retention Time - The amount of time that sewage is allowed to remain in the septic tank.


Reserve pump tank storage - The amount of liquid capacity above the high level alarm float.


Riser - Material used to bring the septic tank access cover to grade.


Sand - The largest particle size considered soil.


Sand Filter - A type of advanced treatment unit.


Schematic - A simple diagram not necessarily drawn to scale.


Scum - The floating layer in the septic tank.


Seepage Pit - A vertical pit in the ground used for dispersal.


Septage - The material removed from a septic tank.


Septic System - System used to treat and disperse of sewage.


Septic Tank - Primary treatment occurs in this box in the ground.


Sequencing Batch Reactor - A type of advanced treatment unit.


Service Interval - Scheduled amount of time between maintenance events.


Service Provider - The firm conducting routine maintenance or emergency service calls.


Setback - Distance between septic system components and site features.


Sewage - Raw sewage from the building.


Sewer Pipe - Another term for building sewer.


Silt - A soil particle size.


Site Evaluation - An initial step in the evaluation of the building site for septic system feasibility.


Site Layout - The layout of the features on a site drawn on a paper.


Site Reconnaissance - An site visit by an engineer to assess the septic system feasibility.


Site Use - Generally categorized into residential, commercial, etc.


Slope - The amount of vertical rise divided by the horizontal run. Generally expressed as a percentage.


Sludge - The material settled to the bottom of the septic tank.


Soil - Material used to treatment effluent.


Soil Absorption System - Anther term for dispersal field.


Soil Auger - Device used to drill about five feet deep to observe subsurface conditions.


Soil Investigation - Generally consisting of soil profiles and percolation testing.


Soil Probe - Anther type of soil auger, when rather than spinning the device is simply pushed into the ground.


Soil Profile - An excavation is dug and an engineer evaluates the subsurface conditions.


Solids - Material settled to the bottom of a septic tank.


Stream - A feature that has setback requirements to septic system components. 


Subsurface discharge - Discharge of effluent under the ground surface.


Subsurface Investigation - Soil profiles and percolation testing.


Suitable Soil - Effective soil beneath the leach field.


Surface Water - Important to keep on the surface.


Surfacing Effluent - A signal that septic system care needs to be given.


Tank Backfill - Soil or aggregate that is placed around the septic tank when installing, must be properly compacted.


Time dosing - discharge is based on an amount of time rather than demand dosing


Transport Pipe - Effluent transport pipe


USDA Soil Classification System - Soil classification system generally used for leach field investigation purposes.


Variance - A deviation from the typical practices.


Venting - Passive or sometimes active venting of the septic tank and/or leach field


Vertical Separation - Vertical distance between a feature and septic system components.


Wastewater - Sewage, untreated or effluent


Watercourse - Streams, rivers, lakes, drainageways


Well - A shaft into the ground intersecting a groundwater aquifer.


Wet-Weather Testing - Subsurface investigation conducted during the wet season


Working Volume - The liquid capacity between the pump off and pump on positions.



Have you heard other terms? Give us a call and we can explain what those mean as well.