What Contaminants to Test for in Oklahoma Well Water
Your Well Doesn't Come With a Warning Label
When you turn on a faucet in Oklahoma City, the water you drink has been tested for over 100 contaminants before it reaches your glass. Somebody at a treatment plant is watching monitors, adjusting chemicals, filing reports, answering to regulators.
When you turn on the faucet from a private well in Blanchard, Harrah, or anywhere else outside municipal limits? That water hasn't been tested by anyone. There's no monitor. No report. No regulator. Just whatever the aquifer is delivering today, passed through whatever your well casing and plumbing happen to contribute along the way.
That's not a scare tactic — it's a fact that surprises about half the well owners I talk to. They assumed somebody was checking. Nobody is. It's your well, your water, your responsibility. Understanding how often to test is the first step. Knowing what to test for is the second.
Think of it like a physical exam. Your doctor doesn't just check your blood pressure and send you home. They order a panel tailored to your age, your history, your risk factors. Well water testing works the same way — the right panel depends on where you live, what's around you, and what you're exposed to.
The Bottom Line: At minimum, test annually for bacteria and nitrates. Then add arsenic, lead, pesticides, VOCs, or PFAS based on your specific location and surrounding land use. Oklahoma wells face distinct risks from agricultural runoff, oilfield contamination, and naturally occurring minerals that differ region by region.
Priority 1: Bacteria — The Non-Negotiable
If you test for nothing else, test for coliform bacteria. It's the vital signs check of water testing — the very first thing we look at.
Total coliform bacteria aren't necessarily dangerous themselves. They're indicator organisms — their presence tells you that your well has a pathway for surface contamination. It's the equivalent of finding ants in your kitchen. The ants aren't the real problem; the crack they came through is.
If total coliform comes back positive, the next step is testing for E. coli. E. coli means fecal contamination — from a failing septic system, livestock manure, wildlife. In clinical terms, it's the difference between an elevated white blood cell count (concerning, needs investigation) and a positive blood culture (we have a definite problem).
Oklahoma risks:
- Poor well seals that let surface water trickle in during storms
- Proximity to septic systems or livestock — more common than people realize in Oklahoma's rural-suburban fringe
- Flooding that overwhelms well casings — and Oklahoma floods with conviction
- Aging well infrastructure — many rural Oklahoma wells are decades old with minimal maintenance
Testing frequency: Annually, and immediately after any flooding or well work.
Priority 2: Nitrates — The Invisible Infant Danger
Nitrates are the reason I get emphatic with families who have babies and well water. The EPA's maximum contaminant level is 10 mg/L, and at that concentration, something genuinely terrible can happen to an infant.
Blue baby syndrome — methemoglobinemia, if you want the clinical name — occurs when nitrate converts to nitrite in an infant's digestive system, which then binds to hemoglobin and prevents it from carrying oxygen. The baby's blood is functionally incapable of delivering oxygen to tissues. The skin turns blue. Without treatment, the brain is starved of oxygen.
I've watched oxygen deprivation events in clinical settings. I don't say this to frighten you. I say it because testing for nitrates takes one sample, costs very little, and removes any uncertainty about whether your infant is safe drinking formula made with your well water.
Where do nitrates come from in Oklahoma?
- Agricultural fertilizers — Oklahoma's crop operations spread nitrogen across millions of acres. Rain carries it into the water table
- Livestock waste and feedlot runoff — Concentrated animal operations are a significant nitrate source
- Septic system leachate — Failing or improperly maintained septic systems leach nitrogen compounds into groundwater
- Widespread in rural Oklahoma — If you're outside city limits, assume nitrates are a possibility until testing rules them out
Testing frequency: Annually. More often if pregnant women or infants are in the household.
Priority 3: Heavy Metals — What Your Geology and Plumbing Are Hiding
Arsenic
Here's a prediction error: arsenic in well water is more often a gift from Mother Nature than a sign of contamination. Certain Oklahoma rock formations contain naturally occurring arsenic that dissolves into groundwater over geological time. You can have a pristine, well-maintained well on untouched land and still pull arsenic from the aquifer.
The EPA limit is 10 parts per billion. Chronic exposure above that level is associated with skin, bladder, and lung cancers. It's colorless, odorless, tasteless. The only way to know is to test.
Testing frequency: At least once to establish your baseline. If your area has known arsenic geology, consider retesting every few years.
Lead
Lead in well water usually doesn't come from the well itself — it comes from the last fifty feet of pipe before your glass. Old plumbing, lead solder on copper joints (common in homes built before 1987), and older brass fixtures can all leach lead into water that was perfectly clean when it left the aquifer.
The insidious thing about lead in drinking water is that it accumulates. Low levels don't cause symptoms. By the time you notice, the damage — particularly to developing brains — is already done.
Testing frequency: At least once, especially if your home has older plumbing.
Iron and Manganese
Not health hazards at typical levels, but they'll make your life annoying. Iron stains everything orange. Manganese stains everything black. Both make water taste metallic. Both are extremely common in Oklahoma aquifers — this is red clay country, and the iron has to go somewhere.
If you're seeing rusty stains on fixtures or mysterious dark deposits, iron or manganese is almost certainly the culprit. Testing quantifies the problem and guides treatment choices.
Testing frequency: Every 3 years, or whenever you notice staining or taste changes.
Priority 4: Oilfield Contaminants — Oklahoma's Unique Legacy
This is the testing category that's uniquely ours. Oklahoma has been drilling for oil since before statehood, and the early decades of extraction were not exactly characterized by environmental consciousness.
"Oklahoma has over 300,000 documented oil and gas wells. Every one of them interacts with the same aquifers your drinking well taps. The legacy of a century of extraction doesn't just disappear because the pumpjacks stopped."
Contaminants associated with oil and gas operations include:
- Chlorides / saltwater — Produced water from oil wells is extremely salty. Spills, leaks, and historic disposal practices have contaminated groundwater in multiple Oklahoma counties. If your well water starts tasting salty, this is first on the suspect list
- Benzene and VOCs — Fuel spills, underground storage tanks, and historic waste disposal can release volatile organic compounds that migrate through groundwater. Benzene is a known carcinogen
- Barium — Associated with drilling operations and drilling fluids. Not a common well water contaminant, but worth testing if you're within a mile of active or abandoned well sites
Testing frequency: Baseline test if you're near active or historic oil and gas operations. Retest after any reported spill or if you notice taste changes.
Priority 5: Agricultural Chemicals
If your property is in or near farming country — and in Oklahoma, "near farming country" describes most of the state — pesticides and herbicides deserve attention:
- Pesticides — Various herbicides and insecticides used on crops can reach groundwater through normal application and rain infiltration
- Atrazine — One of the most commonly detected herbicides in US groundwater. Widely used on corn and sorghum, both significant Oklahoma crops. Atrazine persists in groundwater for years and has been linked to endocrine disruption
Testing frequency: A baseline test if you're near agriculture. Then retest as conditions warrant — new crops, new pesticide applications, heavy rain events that could accelerate infiltration.
The Full Picture: Testing by Location
Here's the cheat sheet I wish someone had given me when I started testing wells across Oklahoma:
| Your Location | Priority Tests (Beyond Basics) |
|---|---|
| Near agriculture | Nitrates, pesticides, atrazine |
| Near oil/gas operations | Chloride, VOCs, barium, benzene |
| Older home (pre-1987) | Lead (from plumbing, not well) |
| Near military base/airport | PFAS ("forever chemicals") |
| Known arsenic geology | Arsenic baseline |
| Experiencing earthquakes | Full panel — seismic activity can disrupt well integrity |
| Near landfill or industrial site | VOCs, heavy metals |
Start Simple: If you've never tested your well, start with bacteria, nitrates, and pH. That's your triage panel — it catches the most common and dangerous problems. Then add location-specific tests based on what's around you. You don't need to test for everything on day one, but you need to test for something.
What Your Results Actually Mean
When results come back, you'll see comparisons against two types of standards:
- Maximum Contaminant Level (MCL) — The EPA's enforceable limit for public water systems. These are the "this-level-is-associated-with-health-effects" numbers. Your private well isn't legally subject to MCLs, but they're the best reference point we have
- Secondary standards — Aesthetic guidelines for taste, odor, and appearance. Exceeding these won't hurt you, but it will annoy you — stained laundry, funny taste, cloudy water
The tricky part is context. A single elevated result might mean "your aquifer has always been this way" or "something just changed." That's why baseline testing and keeping records matters. One data point is a fact. Multiple data points over time are a story.
The Honest Assessment
Not every well in Oklahoma has contaminated water. Most don't, in fact. The vast majority of wells I test come back within normal ranges for everything that matters. That's the good news.
But the wells that do have problems? Their owners almost never knew until they tested. Because contaminated water doesn't advertise. It doesn't smell wrong. It doesn't taste warning. It just flows, clear and quiet, carrying whatever the ground put into it.
Testing gives you information. Not fear — information. And information is what lets you make decisions instead of guesses.
Not Sure What to Test For?
Start with the basics. I'll help you determine the right testing scope for your specific location and situation — no unnecessary tests, no skipped risks.
Schedule Well Water Testing →