Well Water in the Mohawk Valley: Testing, Treatment & What’s In It
Quick Summary: About a third of Montgomery County and nearly 40% of Columbia County draw their water from private wells — roughly 40,000 people across the two counties. Nobody tests that water but the homeowner.
In Montgomery County, 16,526 of 49,642 residents get their water from a private well. In Columbia County it’s 23,304 of 61,509. That’s roughly 40,000 people across the two counties this office serves, drawing water straight out of the ground with no utility between them and the aquifer. Towns like Cooperstown, West Winfield and the rural stretches between Herkimer and Oneonta sit well outside any municipal district.
Private wells aren’t covered by the Safe Drinking Water Act. The EPA doesn’t regulate them, and New York doesn’t require routine testing of an existing well. Whatever the aquifer holds arrives at the kitchen tap unchanged.
What’s actually in the groundwater here
There’s a useful piece of public evidence sitting in the middle of the valley. The Village of Fultonville runs its public supply off two drilled wells, each 190 feet deep, pumping from the same unconfined aquifer that private wells in the area tap. The Village publishes what comes out of them every year.
Their treatment process is built around softening — removing hardness, iron and manganese — before the water is chlorinated and sent out. That tells you what the raw groundwater carries, because a village doesn’t install softening equipment for water that doesn’t need it.
Even after that treatment, iron still registered at 87.6 µg/L in the Village’s 2025 sampling, and manganese ranged from 9.9 to 52.0 µg/L across four quarterly samples. Both are inside their 300 µg/L limits, and the Village treats its water before it reaches customers. A private well a few miles away is pulling from the same formation with no softener, no filter and no chlorine unless the homeowner installed them.
Iron and manganese are what produce the orange-brown staining in sinks, tubs and laundry, and the metallic taste that shows up strongest first thing in the morning. An iron filter handles them at the point of entry. Hardness — the calcium and magnesium the same limestone geology contributes — is what scales fixtures, spots dishes and shortens the life of a water heater, and that’s a water softener‘s job.
Road salt reaches the aquifer
Chloride in Fultonville’s water ran between 188 and 218 parts per million across its four 2025 samples, against a limit of 250. For a groundwater supply that is high, and softening doesn’t remove chloride — so that number reflects what’s in the aquifer, not what the treatment plant added.
The state’s own source water assessment for those wells names the New York State Thruway as one of the pressures on them. Decades of winter salt on highways and county roads works down through soil into shallow groundwater, and a well sited near a plowed road is exposed to the same thing. Chloride doesn’t stain or smell. It shows up as a faintly salty or flat taste, and on a test report.
A village well gets a treatment plant and quarterly lab reports. A private well a few miles away, pulling from the same aquifer, gets whatever the homeowner decides to install.
What a private well is exposed to that a village well isn’t
New York’s health department rates every public water source for how vulnerable it is to contamination. The rating for the Fultonville wells is blunt: very high susceptibility to industrial organic compounds, and high susceptibility to bacteria, viruses, halogenated solvents, pesticides, nitrates, metals and protozoa.
The reasons given are a permitted discharge facility, a hazardous waste site, a recorded hazardous substance spill, residential activity and the Thruway — all within the assessment area, all sitting above an unconfined aquifer with high hydraulic conductivity. Unconfined means no impermeable layer caps it. High conductivity means what reaches the water table moves through it quickly.
Those ratings describe the ground, not any one well, and they’re the reason the Village disinfects. A private well in the same ground has the same exposure and no disinfection step. That’s also the practical difference between a shallow dug or driven well and a deeper drilled one: depth buys some protection from surface contamination, at the cost of picking up more dissolved mineral on the way.
Two more things occur naturally in Central New York bedrock and give no warning at all. Arsenic and radon are both colorless, odorless and tasteless at the levels that matter. Nitrates behave the same way and are a real risk to infants and pregnant women — a concern anywhere near working farmland, which describes most of this valley.
How often to test, and what to ask for
Once a year, at minimum, for total coliform bacteria, nitrates, total dissolved solids and pH. Given what’s documented in this aquifer, it’s worth adding iron, manganese, hardness, chloride and sodium to the panel — and arsenic at least once, since a single result tells you whether your particular bedrock carries it.
Test immediately, outside the annual schedule, if any of these happen:
- The well was opened or exposed for any reason (construction, a pump repair, flooding)
- A new taste, odor or smell appears: metallic, musty, or the rotten-egg sulfur smell that’s strongest at the hot tap
- The water turns cloudy, or takes on a red, brown or yellow tint
- Water pressure changes noticeably
- A neighbor’s well tests positive for something, or there’s been flooding or a spill nearby
Until you know what changed, use bottled water for drinking and cooking. Between tests, look the wellhead over a few times a year: cap sealed and secure, casing and fittings sound, nothing corroding or leaking, and the grade carrying runoff away from the well rather than toward it.
Where to get a well tested locally
For a certified lab result, use a laboratory approved under New York’s Environmental Laboratory Approval Program (ELAP) — that’s the standard a result needs to meet if you’re ever using it for a real estate transaction or a health question.
The Montgomery County and Columbia County health departments both provide guidance for private well owners, and Cornell Cooperative Extension Columbia-Greene publishes private well testing guidance for homeowners in this region. Some county testing clinics are seasonal, so check current dates and fees before you plan around one.
Matching treatment to the test result
Treatment follows the test, not the other way around. Hardness calls for softening. Iron and sulfur each call for dedicated filtration — the rotten-egg smell is hydrogen sulfide gas, harmless at typical levels and still the complaint people call about most. Bacteria may call for disinfection. Chloride, sodium, nitrates and arsenic don’t respond to a softener or a sediment filter at all; those are handled at the tap with reverse osmosis drinking water filtration.
Most wells in this valley need more than one thing. A common setup is a softener and an iron filter treating the whole house, with an RO system under the kitchen sink for drinking and cooking.
For sorting out a taste, odor or staining problem and deciding what to install, a free in-home water test covers the common culprits on the spot. It isn’t a substitute for an ELAP lab panel on bacteria, nitrates or arsenic — those need a certified lab.
Culligan of Mohawk Valley has been testing and treating well water in Herkimer, Cooperstown, Oneonta, Cobleskill, Hudson and the surrounding communities for decades. Bring us a lab report or let us test what’s coming out of the tap, and we’ll tell you what it would take to fix.
