Septic System Types
Onsite wastewater treatment, or septic for short, covers many kinds of system. Each one treats the wastewater of a building and returns it safely to the ground. They differ in how the effluent is treated and how it reaches the soil: by gravity or under pressure, in trenches, in a bed of sand, through drip tubing or from spray heads.
landplan.io knows each system by a short code, such as LTF or MLS. You see the codes in Details, in the Auto design system list and on the report.
Which systems you can design
The systems on offer come from your state's (or province's) configuration. A system shows in Smart design, in the Contour tool and in Details only when your area allows it and has a form for it. If a system you use is missing, please contact us.
You design a system in one of three ways:
- Smart design and Auto design (the Design button) pick a system that fits the site and place it for you. See Smart Design and Auto Design.
- Trench and Contour (in Tools > Septic design > System) draw the systems whose trenches or bed run along the contour. See Contour Systems.
- Spray zone and Drip design draw spray and drip zones. See Spray Tool and Drip Distribution.
The system types
| Code | System | What it is | When it is used | Drawn with | Read more |
|---|---|---|---|---|---|
| LTF | Leaching trench field | Trenches of gravel or a gravelless product, fed by gravity or by a pump. | Soil with good depth above the limiting condition. | Trench + Contour, Smart design, Auto design | Leaching Trench Fields |
| MLS | Mounded leaching system | A pressure-dosed aggregate bed on a mound of sand fill above the ground. | A shallow limiting condition, such as a high water table or bedrock. | Trench + Contour, Smart design, Auto design | Mounded Leaching Systems |
| LPP | Low pressure pipe | Small pressurized laterals with drilled orifices in shallow trenches. | Slow or shallow soils where the effluent must be spread evenly. | Trench + Contour, Smart design, Auto design | Low Pressure Pipe |
| Drip | Drip distribution | Drip tubing with emitters, laid in zones and dosed by a timer. | Steep, wooded or tight sites, usually after advanced treatment. | Trench + Contour, Smart design, Auto design, Drip design | Drip Distribution |
| Spray | Spray distribution | Treated and disinfected effluent sprayed over the ground by spray heads. | Where your area allows surface application. | Spray zone, Smart design | Spray Distribution Systems |
| AG | At-grade system | A pressure-dosed aggregate bed laid on the ground surface and covered with a soil cap. | A limiting condition too shallow for trenches, but not shallow enough to need a mound. | Trench + Contour (where offered), Smart design, Auto design | Soil Absorption Systems |
| ATL | Infiltrator Advanced Treatment Leachfield | Rows of a proprietary leaching pipe in a bed of sand. | Where your area approves the product, often with sizing or depth credits. | Trench + Contour, Smart design, Auto design | Large Diameter Pipe |
| AES | Infiltrator Advanced Enviro-Septic | Rows of a proprietary large diameter pipe in a bed of sand. | Where your area approves the product, often with sizing or depth credits. | Trench + Contour, Smart design, Auto design | Large Diameter Pipe |
| CAF | Cut and fill (gravity) | A bed of stone cut into the soil, with fill above grade where the bed is shallower than its height. | In-ground beds; some states call it an In-Ground Bed. | Trench + Contour (where offered), Smart design, Auto design | Soil Absorption Systems |
| CAFP | Cut and fill, pressure dosed | The same bed, fed by pressure laterals. | Where the bed must be dosed evenly. | Trench + Contour (where offered) | Soil Absorption Systems |
| ET | Evapotranspiration bed | A bed that loses the effluent to the air through evaporation and plants. | Dry climates. | Trench + Contour (where offered) | Soil Absorption Systems |
| GST | GeoMatrix GST | A gravelless sub-surface trench product. | Where your area approves it. | Trench + Contour (where offered) | Soil Absorption Systems |
| Oscar | Oscar drip | A proprietary drip system. | Where your area approves it. | The map's tools | Drip Distribution |
| L (Lagoon) | Lagoon | An open pond that treats and evaporates the effluent. | Large lots in areas that allow lagoons. | The map's tools | Soil Absorption Systems |
| NPDES | Discharging system | Highly treated effluent discharged to a stream or ditch under a permit. | Where no soil system fits. | The map's tools | Designing a Discharge System |
| Custom | Custom soil absorption system | Not a system you pick: the name Details gives a design with more than one kind of absorption system on the map. | A mound and trenches on one site, for example. | Any of the above | Details & Report PDF |
Your configuration may also list a leaching gallery (LG), vertical or horizontal seepage pits (VSP, HSP), an evapotranspiration absorption bed (ETA), a bottomless media filter (BMF) or a Glendon BioFilter (GLEN). Details sizes them. The contour tool draws the seepage pits where your area offers them; draw the others with the map's tools. See Other system types.
Treatment units
Some parts of a design are not a system type but treat the effluent before it reaches the soil. You add them with the Tank tool as an Advanced Treatment Unit:
- Aerobic Treatment Units add air to the wastewater.
- Filtration Systems pass it through sand, peat, textile or other media.
An advanced treatment unit on the map changes how the absorption area is sized. See Aerobic Treatment Units.
The parts every system shares, such as the septic tank, are described in Common Components.
What Smart design shows for each system
When you pick a system in Smart design, each one has a badge:
| Badge | Meaning |
|---|---|
| Allowed · fits | Your soil tests allow it, and Smart design can place it on the parcel. |
| Allowed · tools | Your soil tests allow it, but you draw it yourself with the map's tools. This is the case for systems Smart design can't generate, such as a lagoon, or when your configuration has no form for the system. |
| Allowed · no room | Your soil tests allow it, but it doesn't fit inside the setbacks. |
| Allowed · soil too shallow | The soil tests allow it, but there isn't enough soil over the limiting condition for it here. A mound or a bed on sand can make up the separation. |
| Not allowed | Your soil tests don't allow it. |
Smart design and Auto design can generate the mound (MLS), leaching trench (LTF), low pressure pipe (LPP), drip (Drip), at-grade (AG), ATL, AES and cut and fill (CAF) systems. Smart design also places spray heads for a spray system (Spray). See Smart Design and Auto Design.
Related guides
From the landplan.io blog: