There’s a loose patchwork of septic standards in Michigan
Because of the lack of state standards to assure replacement of failing septic systems, some counties, townships, cities, and villages are enacting local ordinances in place of statewide requirements, but they are relatively few out of Michigan’s approximately 2,000 local units of government.
Only 11 of 83 Michigan counties have ordinances that require septic tank inspection at the time property is sold. Within the first 6 years of implementing their ordinances, two Michigan counties found 1,000 failed septic tanks, and 300 homes without any septic system or other wastewater treatment.
How septic systems work (and what happens when they don’t)
Septic systems are small-scale wastewater treatment options, used when a home or complex cannot easily be connected to a municipal sewer system.
Raw sewage and wastewater (e.g., bath water and dishwater) are first pumped from the home into the septic tank. This is an underground, sealed, concrete tank where the household waste is treated. Here, solid waste sinks to the bottom of the tank and materials such as oil form a layer of scum on top. Bacteria then break down the solid waste, while the wastewater migrates out of the septic tank and into the drain field.
Perforated pipes distribute the liquid wastewater throughout the drain field. Once out of the pipes, the wastewater effluent seeps through a gravel layer, then through the soil. The gravel and soil filter the wastewater before it flows into the groundwater or nearby surface water (streams, ponds, lakes, etc.).
Leaking or malfunctioning septic systems allow organic wastewater compounds like nitrate and E. coli to percolate through the soil and enter the groundwater. Leakage and effluent runoff are also major contributors to E. coli levels in surface water.
The Michigan Department of Environment, Great Lakes, and Energy (EGLE) has identified approximately 200 rivers, lakes, and beaches with E. coli levels over the EPA limit.
Between 2013 and 2014, an estimated 5.7 billion gallons of untreated sewage from failing septic systems were pumped into surface water in Michigan. Failing septic systems have been correlated with disease. A 2003 study found that septic system densities were associated with endemic diarrheal illness in central Wisconsin.
Septic systems and emerging contaminants
Human wastes are not the only pollutants that failing septic tanks are releasing to groundwater and surface water. So-called emerging contaminants are found in household wastes, whether they discharge to publicly owned sewage systems or septic tanks. 
Twenty different studies on septic systems have identified 45 contaminants in septic effluent, including pharmaceuticals, personal care product ingredients, chemicals in cleaning products, flame retardants, hormones (both natural and synthetic), and other common substances such as caffeine.
Septic systems are somewhat effective at removing chemicals such as acetaminophen, caffeine, and alkylphenols, a common group of ingredients used in cleaning products. But some chemicals remain largely untreated, including the carcinogenic flame retardant TCEP, an anti-epilepsy drug called carbamazepine, and the antibiotic sulfamethoxazole.
One cause of the septic system pollution problem is homeowners’ lack of awareness. A 2018 study of mid-Michigan residents likely to have septic systems, conducted by Public Sector Consultants, found:
- Approximately 30 percent of residents did not know they have a septic system.
- The average age of septic systems was 28 years old.
- Forty-three percent of respondents indicated they had not had their system pumped within the last 5 years, and 25 percent indicated that they did not pump or maintain their system on a regular basis.
- Only 15 percent of residents were aware of the normal lifespan of a septic system.
Don’t Overload the Commode: Only put things in the drain or toilet that belong there. For example, coffee grounds, dental floss, disposable diapers and wipes, feminine hygiene products, cigarette butts, and cat litter can all clog and potentially damage septic systems.
Think at the Sink: Avoid pouring fats, grease, and solids down the drain. These substances can clog a system’s pipes and drainfield.
Shield Your Field: Remind guests not to park or drive on a system’s drainfield, where the vehicle’s weight could damage buried pipes or disrupt underground flow.
Don’t Strain Your Drain: Be water-efficient and spread out water use. Fix plumbing leaks and install faucet aerators and water-efficient products. Spread out laundry and dishwasher loads throughout the day—too much water at once can overload a system that hasn’t been pumped recently.
Pump your Tank: Routinely pumping your tank can prevent your septic system from premature failure, which can lead to groundwater contamination.
Protect It and Inspect It: Homeowners should generally have their system inspected every three years by a qualified professional or according to their state or local health department’s recommendations. Tanks should be pumped when necessary, typically every three to five years.
Test Your Drinking Water Well: If septic systems aren’t properly maintained, leaks can contaminate well water. Testing your drinking water well is the best way to ensure your well water is free from contaminants.
The story map uses the most recent available data for groundwater wells, extractions, contamination sites, and more to create interactive mapping applications – all streamlined for faster loading. There are new maps showing industrial and irrigation wells, Michigan’s aquifers, and how various sectors utilized groundwater in 2021. There are also new interactive graphics describing Michigan’s groundwater usage.
