Septic, well and site-work glossary

Use these to read an estimate or ask a sharper question. A term alone does not diagnose a system or decide whether work is necessary.

Leachfield (drain field)

The network of perforated pipe in stone or chambers where soil finishes treating the liquid that leaves the septic tank. The consumable part of a septic system.

Effluent

The clarified liquid in the middle of the septic tank: the only part that should leave the tank and flow to the leachfield.

Baffle / sanitary tee

The fittings at the tank's inlet and outlet that keep floating scum and settled sludge inside the tank instead of flowing out to the field.

Effluent filter

A removable screen at the tank outlet that catches solids before they reach the leachfield. Cleaned at pump-out; a cheap part that protects an expensive one.

Distribution box (D-box)

The junction that splits effluent evenly among the leachfield lines. A shifted D-box is a common reason one line floods while others stay dry.

Mound system

A leachfield built up above natural grade in sand, used where soil is too shallow, too wet or too slow for a conventional in-ground field.

Perc test (percolation test)

A field measurement of how fast water moves through the soil, distinct from the soil excavation, texture and structure evaluation used by Vermont’s current design rules.

Test pit

A backhoe pit dug so a designer can read the soil profile and find the seasonal high water table and any ledge.

Isolation distance / setback

The required separation between system parts and features like wells, surface water and property lines. Set by the state Rules; confirm current figures with your regional office.

Designer (Class 1 / A / B / BW)

The licensed person the Rules require to design a Vermont system. The class sets what system types and flows they may design.

Grout seal

The cement seal around a well casing that keeps surface water and shallow contamination out of the borehole.

Submersible pump

The pump that sits down inside a drilled well and pushes water up to the building's pressure tank.

Pressure tank

The tank inside the building that holds water under pressure so the pump does not run every time you open a tap.

Yield / flow rate

How much water a well produces, measured in gallons per minute during drilling. Sets whether storage or a different water strategy is needed.

Curtain / interceptor drain

A gravel-filled trench with perforated pipe that intercepts groundwater moving downhill before it reaches a wet area or foundation.

Culvert

A pipe that carries a ditch or stream under a driveway or road so water keeps moving instead of ponding or washing out the crossing.

Daylight outlet

The point where a drain pipe reaches the surface and releases water, ideally downhill and away from structures.

Ledge

Shallow bedrock. The most common reason a Vermont site needs a raised or mound system rather than a conventional in-ground leachfield.