From the Lab by ETR Laboratories

Michigan has more private residential wells than almost any other state in the country. About 2.6 million Michigan residents get their drinking water from private wells, and those wells are not routinely monitored by the state or subject to federal drinking water standards. Nobody is checking your water for you. That responsibility sits entirely with the homeowner.

Most Michigan well owners understand this in theory. But understanding it and acting on it are two different things, and the gap between them is where the real risk lives. This guide is meant to close that gap.

What Michigan’s water history should tell every well owner

It’s worth starting with Flint, not to relitigate a decade-old crisis, but because of what it demonstrated. In April 2014, Flint switched its municipal water source to the Flint River. Officials failed to apply corrosion inhibitors. Lead leached from aging pipes into the supply of roughly 100,000 residents before the city switched back 17 months later. Flint was a city water system with regulators, engineers, and oversight. It still failed. The lesson for private well owners is not that their situation is as bad as Flint’s. It’s that water quality is not self-correcting, and assumptions are not a testing strategy.

Michigan’s industrial legacy compounds this. The state has confirmed over 300 PFAS contamination sites, more than any other state in the country, with over 11,000 sites statewide suspected of potential contamination. Sources range from military bases and manufacturing plants to landfills that accepted industrial waste for decades. And those sources don’t announce themselves. A family in Kent County spent 25 years living next to what they thought was a Christmas tree farm, which turned out to be a former dump site for Wolverine World Wide tannery waste coated in Scotchgard. Their first PFAS test came back at 24,000 parts per trillion, far exceeding the federal limit of 4 parts per trillion set in 2024. Subsequent tests reached as high as 100,000 ppt.

More recently, a 2025 investigation in Cadillac revealed something nobody expected: some residents may have unknowingly contaminated their own wells by flushing common household products like laundry detergent and floor wax into septic systems, which then allowed PFAS-tainted wastewater to slowly infiltrate the aquifer below. It isn’t just factories and industrial sites. It’s in the products under most people’s sinks.

The top contaminants Michigan well owners should test for

1. PFAS (“Forever Chemicals”)

This is Michigan’s most urgent and widespread water contamination issue. PFAS are colorless, odorless, and tasteless. They cannot be detected without laboratory analysis. Private wells have no required testing for PFAS, and the state has no authority to regulate them. The responsibility to test falls entirely on the homeowner. Given the density of contamination sites across the state, any Michigan well owner who has never tested for PFAS should do so.

2. Arsenic

Michigan has naturally higher arsenic levels in groundwater due to the state’s geology. Arsenic cannot be seen or tasted, and a laboratory analysis specifically designed for detecting arsenic is the only way to determine the level in a well. Long-term exposure to arsenic in drinking water is linked to bladder, lung, and skin cancer, as well as cardiovascular disease. The EPA’s maximum contaminant level for arsenic is 10 parts per billion, but the agency sets its health goal at zero. EGLE recommends that Michigan homeowners have their well water tested for arsenic, and if levels exceed 10 ppb, advises against using the water for drinking or cooking without treatment.

3. Iron and Manganese

Iron is naturally occurring in Michigan groundwater, and in a USGS study of Oakland County wells, more than half of the wells sampled exceeded the EPA’s secondary limit for iron and nearly half exceeded it for manganese. At elevated levels, iron causes staining on fixtures and laundry, a metallic taste, and orange or brown water. Manganese at higher concentrations is associated with neurological effects, particularly in children. These are among the most common well water complaints in Michigan and among the most consistently undertested.

4. Nitrates

Nitrates enter groundwater from agricultural fertilizers, septic systems, and animal waste. They’re particularly concerning for infants, where high nitrate exposure can cause a condition called methemoglobinemia, or blue baby syndrome. Rural Michigan well owners, especially those near farmland or with older septic systems, should include nitrates in any comprehensive test. The EPA’s limit is 10 mg/L, but contamination above this level is not unusual in agricultural areas.

5. Coliform Bacteria and E. coli

These are the baseline indicators of microbiological contamination. Heavy rainfall, flooding, aging well casings, and proximity to septic systems can all introduce bacteria into a well. The CDC recommends testing private well water for coliform bacteria and nitrates at least annually. Many Michigan homeowners test for everything else and skip the bacteria panel because they assume their well is sealed. A sealed well can still be compromised.

Radon: worth noting

Radon is a legitimate concern for private well owners in parts of the country where granite bedrock is common, particularly New England. Michigan’s own environmental agency notes that the state is not among the areas where radon from well water is expected to make a significant contribution to indoor air concentrations. That said, radon is present in every Michigan county and testing is inexpensive. If you’ve already identified elevated radon in your home’s air and you’re on a private well, testing your water is a reasonable next step.

A note on PFAS and household products

The Cadillac situation is a reminder that contamination in Michigan isn’t limited to what’s upstream of your well. Common household products including certain laundry detergents, floor waxes, and personal care products contain PFAS. When flushed into a septic system, those chemicals can infiltrate the surrounding groundwater over time. This doesn’t mean every Michigan homeowner with a septic system has a PFAS problem. It means that PFAS exposure is harder to predict than most people assume, and testing is the only way to know.

How to approach this

Testing your well annually for bacteria and nitrates is a reasonable baseline. Every few years, or any time you notice a change in taste, odor, or color, a more comprehensive panel makes sense. If you’re near any of Michigan’s documented contamination sites, near a military base, former industrial property, or agricultural land, PFAS testing should be part of that comprehensive panel.

At ETR Laboratories, we test for all of the above. We work with homeowners across the country and can guide you through what a comprehensive well water panel covers and what makes sense given your location and situation. Contact us for a free consultation or browse our water testing options.

Sources

Inside Climate News / Circle of Blue — Michigan’s Other Water Crisis: PFAS’s Prevalence in Private Wells

Bridge Michigan — Michigan’s Newest PFAS Threat: Contamination from Household Septic Systems

Michigan EGLE — Arsenic in Well Water

USGS — Ground-Water Quality Atlas of Oakland County, Michigan

Michigan EGLE — Drinking Water and Wells / PFAS Response

CDC — Guidelines for Testing Well Water