Glossary

Accreditation Program: The Michigan Local Public Health Accreditation Program, running since 1998. MDHHS, MDARD, EGLE and local health departments jointly review each health department on a three-year cycle, confirming it has a legally adopted sanitary code with enforcement provisions and evidence of enforcement. It ensures a code exists; it does not make codes uniform.

Baffle: A barrier inside the septic tank controlling flow between compartments and keeping solids from reaching the drainfield.

County Sanitary Code: The document that actually governs septic systems on your property. Because Michigan has no statewide code, each local health department adopts its own, and they differ meaningfully between counties.

Drainfield: Where treated wastewater disperses into soil for final treatment. Also called a leach field or absorption field.

EGLE: The Michigan Department of Environment, Great Lakes, and Energy. Its Onsite Wastewater Program provides guidance and oversight, and can review a local decision on appeal, but generally does not override local health department authority.

Effluent: The liquid leaving the septic tank after solids settle out.

Evaluation: An assessment of whether a septic system is functioning as designed. Michigan has no statewide requirement for periodic evaluation, which is one of the central issues Senate Bill 771 addresses.

Holding Tank: A sealed tank with no drainfield, pumped out on a schedule rather than dispersing effluent into soil. Some Michigan counties permit these where a lot fails soil evaluation; Wayne County mandates them as an alternative in that situation.

Local Health Department: The authority that writes and enforces septic rules in Michigan. There are 45 covering the state's 83 counties, and each adopts its own sanitary code.

MSTA: The Michigan Septic Tank Association. It works with EGLE and local health departments to promote consistent standards through training and advocacy, though it has no regulatory power.

Onsite Wastewater Treatment System: The formal term for a septic system. Michigan's proposed legislation uses this phrasing throughout.

Percolation Test: A test measuring how quickly water moves through soil, used alongside soil borings to determine what system a site can support.

Perc Rate: Shorthand for percolation rate — how fast soil accepts water. Slow rates on heavy clay, common across Southeast Michigan, limit system options.

Riser: An extension bringing a buried tank access lid to grade. Typically $200 to $400, and it pays for itself within about two pump-outs by removing the excavation charge.

Sanitarian: The local health department official who performs soil evaluations and site assessments, and who inspects installations.

SB 771: Senate Bill 771, sponsored by Sen. Sam Singh and introduced January 28, 2026. It would require EGLE to develop Michigan's first statewide septic code within three years. It advanced from Senate committee in June 2026 and awaits floor action. It is not law.

Setback: The minimum required distance between a septic component and a well, property line, surface water or structure. Set by your county code rather than a statewide standard.

Soil Boring: A sample taken from the ground to assess soil type, depth to bedrock, and depth to the water table. Part of the site evaluation preceding any permit.

Technical Advisory Committee: The group of local health officials, engineers, soil scientists and environmental organizations that Senate Bill 771 would create to guide EGLE in developing statewide rules.

TOST Ordinance: Time of Sale or Transfer ordinance, also called Point of Sale or POS. A local requirement that well and septic systems be inspected before a property is sold. Adopted county by county and community by community in Michigan, since there is no statewide equivalent.

Vertical Separation: The depth of suitable soil beneath a drainfield before reaching a limiting condition such as bedrock or the seasonal high water table. Insufficient separation is a common reason a site fails evaluation.