Private Well Testing in Illinois: What to Test, How Often, and Who to Call
If you are on a private well in the Sauk Valley, nobody is testing your water except you. Here is exactly what to do about that, and when.
If you live in Sterling, Dixon or Rock Falls, a licensed operator samples your water on a federal schedule, an accredited lab runs it, and you get a Consumer Confidence Report every year whether you asked or not.
If you live in Woosung, Grand Detour, Nachusa or Eldena, none of that exists. No utility, no operator, no sampling schedule, no lab contract, no annual report. Your well is regulated when it is drilled and unwatched afterward. Nobody is testing your water. That is how private wells work in Illinois, and this page hands you the job nobody else is doing.
The gap, in numbers
| Community | System ID | Who tests it | What testing found |
|---|---|---|---|
| Dixon | IL1030200 | The city, federal schedule | Radium 226 and 228 at 2.11 pCi/L. EWG guideline 0.05 pCi/L. |
| Sterling (Illinois American Water) | IL1955040 | The utility, federal schedule | Trihalomethanes at 26.1 ppb. EWG guideline 0.15 ppb. |
| Rock Falls | IL1950450 | The city, federal schedule | Arsenic at 1.00 ppb. EWG guideline 0.004 ppb. |
| Woosung, Grand Detour, Nachusa, Eldena | None | You | Nothing found, because nothing was looked for. |
Read that twice. The towns with numbers beside them are being watched, and those utilities are in compliance with federal drinking water standards, as their own reports state. The guidelines quoted are the independent health guidelines from the EWG Tap Water Database, set well below federal legal limits. Legal limits and health guidelines are two different lines, and knowing both is how you decide.
Those rows with no numbers are not clean. They are unmeasured. Detection lists are on the town pages for Dixon, Sterling and Rock Falls. The pages for Woosung, Grand Detour, Nachusa and Eldena are short, and that is why.
What Illinois actually recommends
The Illinois Department of Public Health publishes a schedule short enough to write inside a cupboard door.
| Test | How often | Why |
|---|---|---|
| Bacteria (total coliform) | Every year | The indicator that surface water or fecal material found a path in |
| Nitrate | Every year | The one that matters most with an infant in the house |
| Metals | Every three years | Iron, manganese, lead, arsenic. Slow moving, so three years catches drift |
| VOCs, pesticides, PFAS | If detected nearby | Event driven: a spill, a leaking tank, a plume |
The Illinois EPA says the same: at least once a year for bacteria, every year for nitrate. It adds that radium occurs naturally in the northern third of Illinois in deep rock and groundwater, has been detected in private wells, and can be identified only by testing. Whiteside, Lee and Ogle counties sit in that northern third.
Coliform and E. coli, and what a positive actually means
Total coliform bacteria are not themselves what makes people sick. They live in soil and vegetation as well as in intestines. They are an indicator, tested because they are easy to detect and travel the routes dangerous organisms travel. IDPH frames a positive as a construction question: surface water or fecal material found a path in, usually a cracked casing, failed seal, damaged cap or flooding pit.
E. coli is the second line and it is the serious one. The CDC's language is direct: a positive for fecal coliform or E. coli likely means feces, and the germs in feces, have gotten into your well water. A total coliform positive means find and fix the path. An E. coli positive means stop drinking it today.
IDPH's instruction on any bacteria positive is to boil water for drinking and cooking and disinfect the well. A negative only means nothing was detected that day: a snapshot, not a warranty, which is why the recommendation is annual.
Nitrate, and why it is the one that matters most
If you only ever run one chemical test on a private well, run nitrate. The federal standard is 10 milligrams per liter as nitrogen. IDPH states that levels above 10 mg/L as nitrogen may cause illness in infants six months of age or younger, and advises infants under six months should not drink well water where nitrate is detected. The condition agencies associate with it at that age is infant methemoglobinemia, or blue baby syndrome.
- Boiling makes it worse. IDPH is explicit: do not boil water containing nitrate, because boiling concentrates it. That is the opposite of the instruction for bacteria, and confusing the two is a real risk in a house with a new baby.
- Nitrate is invisible, tasteless and odorless. Every other problem on this page announces itself in a stain or a smell. This one does not.
- Neither a softener nor a carbon or sediment filter removes it. IDPH notes advanced treatment is required: reverse osmosis, distillation, or nitrate selective anion exchange.
Nitrate here is an agricultural and septic signal moving with shallow groundwater. Shallow wells, old wells and wells downgradient of a feedlot or a fertilized field are the ones to watch. Published municipal numbers give the background: Erie measured nitrate at 5.45 ppm and Leaf River at 5.93 ppm, both inside the federal limit of 10 and both well above the 0.14 ppm independent health guideline. A private well in the same countryside has nobody checking.
What a basic test covers, and what it misses
The standard county package is coliform bacteria and nitrate. That is the right start and not the whole picture.
- Hardness, iron and manganese. Not health regulated, so not in the panel, and the source of most complaints people have.
- Radium. Naturally present in northern Illinois deep bedrock, per the Illinois EPA, invisible without a specific test.
- Arsenic. Present in this region's groundwater and detectable by no sense at all.
- Lead, if the home predates 1986 or has brass fixtures.
- Hydrogen sulfide, sulfate and pH. Not health tests, but they decide what treatment works.
Where to get a certified test in Whiteside, Lee and Ogle counties
Bottles for bacteria sampling come from your local health department. IDPH will also interpret your results at no charge.
| County | Health department | Address | Phone |
|---|---|---|---|
| Whiteside | Whiteside County Health Department | 1300 West Second Street, Rock Falls, IL 61071 | 815-626-2230 |
| Lee | Lee County Health Department | 309 S. Galena Ave., Suite 100, Dixon, IL 61021 | 815-284-3371 |
| Ogle | Ogle County Health Department | 907 Pines Road, Oregon, IL 61061 | 815-562-6976 |
Ogle County runs the most visible private water program of the three: sample bottles, testing for bacteria, nitrate and lead, permits for new wells, chlorination instructions and a posted fee schedule with drop off times. Lee County issues permits on all new wells and publishes sheets on nitrate, coliform and radium. Whiteside County's environmental health staff work out of the Rock Falls office. Call before you drive: a bacteria sample has a clock on it.
How to take the sample so the result means something
A good share of bad results are collection errors. IDPH publishes the procedure.
- Run the tap at full flow until the pump has cycled. You want aquifer water, not water standing in the pressure tank.
- Cut the flow back to about the width of a pencil.
- Remove the aerator. Aerators harbour bacteria and will fail an otherwise clean well.
- Open the sterile bottle last. Do not touch the rim or the inside of the cap.
- Fill to the line and no further. The air space is part of the test.
- Move fast. IDPH will not accept a sample received more than 30 hours after collection.
One thing that costs nothing. Walk out and look at your well head. Is the cap sealed and above grade? Is the ground sloped away? Is there standing water, or a pit that floods in spring? Most coliform positives here are a physical path, not a mystery.
What to do after a bad result
- Coliform positive, E. coli negative. Stop drinking it. Boil for drinking and cooking, disinfect the well, then find the path: cap, casing, seal, grade, pit.
- E. coli positive. Do not drink it, cook with it or make formula with it. Bottled water, and call the health department the same day.
- Nitrate above 10 mg/L as nitrogen. Do not boil it. Use an alternate source for anyone under six months while you sort out treatment.
- Any positive. Disinfect, retest, retest again. Two clean samples several weeks apart is what proves it is gone.
- Repeat positives after two disinfections. Get the well inspected. Bleach does not fix a cracked casing.
Events that should trigger a test even if you tested in the spring
The annual schedule is the floor. The CDC lists the situations that override it.
- Flooding, or land disturbance near the well. Any time surface water has been over or near the well head. In the river bottoms this one is not optional.
- Any repair to the well system: pump, pressure tank, casing, pitless adapter.
- A new or newly reopened well. IDPH says to test all new and repaired wells.
- A change in taste, color or smell. Your senses are the only continuous monitoring a private well has.
- A nearby spill, a leaking fuel tank, or a waste disposal site.
- Word of a problem nearby. If a neighbour's well fails, yours is in the same aquifer.
- Someone becomes pregnant, or a child moves in. Learn your nitrate number first.
Testing is not a sales pitch and we do not run a laboratory. Call your county health department, get the bottle, take the sample properly and read the sheet. If it says you have something to treat, that is a conversation we can help with.
Liberty Water sizes, supplies and services treatment equipment. Any installation is performed by a licensed Illinois plumbing contractor. To see what each stage is for, our packages page lays it out.
Questions people actually ask
How often should I test my private well in Illinois?
IDPH recommends bacteria and nitrate every year, metals every three years, and VOCs, pesticides or PFAS only if something has been detected nearby. Illinois EPA gives the same annual guidance for bacteria and nitrate. Test outside that schedule after flooding, after any repair to the well system, or after a change in taste, color or smell.
Where can I get my well water tested in Whiteside, Lee or Ogle County?
Start with your county health department, which supplies the sample bottles. Whiteside County Health Department is at 1300 West Second Street in Rock Falls, 815-626-2230. Lee County Health Department is at 309 S. Galena Avenue in Dixon, 815-284-3371. Ogle County Health Department is at 907 Pines Road in Oregon, 815-562-6976. Call first, since drop off is scheduled.
What does a positive coliform test mean for well water?
It means surface water or fecal material has found a path into your well, usually through the cap, casing, seal or a flooded pit. Coliform is an indicator rather than the danger itself. The CDC notes a high total coliform count makes it likely harmful germs are present too. IDPH advises boiling water for drinking and disinfecting the well.
Is nitrate in well water dangerous for babies?
The federal standard is 10 mg/L measured as nitrogen. IDPH states levels above that may cause illness in infants six months of age or younger, and advises infants under six months should not drink well water where nitrate is detected. Critically, IDPH warns not to boil the water, because boiling concentrates nitrate rather than removing it.
Does a water softener or filter remove nitrate?
No. A softener exchanges calcium and magnesium and leaves nitrate untouched, and a carbon or sediment filter does nothing for it either. IDPH notes that advanced treatment is required. In practice that means reverse osmosis at the drinking tap, distillation, or a nitrate selective anion exchange unit sized for the household.
Do I need to test my well after a flood?
Yes, and it is one of the situations the CDC lists specifically. If surface water has been over or near the well head, assume the well is contaminated until a test says otherwise. Test for total coliform and nitrate, disinfect the well, and retest after disinfection before putting it back into normal use.