Private well guide

Well Water in Illinois: Testing, Rules, Labs and Licensed Contractors

460,451 households in Illinois get their water from a private well. Here is what the state requires, where to get it tested, and who is licensed to work on it.

Find a certified labLicensed contractorsPick my county
277Licensed contractorschecked against state records
31Certified labsfrom the state certified list
102Counties covered
460,451Households on wells9% of households (est.)

About 460,000 Illinois households drink from a private well, only 9% of the state because Chicago and its suburbs are on Lake Michigan water, but the wells are concentrated: Will, Lake, DuPage, McHenry and Kane counties alone have 170,000 well households, and in rural counties like Cumberland, Mason and Shelby it is four homes in ten. Illinois is one of the few states that requires a permit and a health department inspection before a private well is used, and its aquifers carry arsenic, radium and iron that a yearly bacteria test will never show.

Who is in charge of an Illinois well

The Illinois Department of Public Health writes the Water Well Construction Code, licenses the individual water well contractors and pump installers, and delegates the permits and inspections to the county health departments, which is where an owner deals with the program day to day. The contractor files a well construction report with IDPH after the well is built, and the Illinois State Geological Survey publishes the records on its ILWATER map, searchable by address. Water quality after the final inspection belongs to the owner, with the county health department lab, the IDPH state lab and the Illinois EPA accredited commercial labs doing the testing.

What is required, and what is left to you

A permit from the county health department before drilling, a licensed contractor on site, construction and setbacks to the code, disinfection and a passing bacteria sample before the well goes into service, and the construction report. After that Illinois requires nothing: no test at sale and no periodic test, though the seller’s disclosure asks about the water supply and government-backed mortgages want a bacteria, nitrate and lead result. IDPH’s advice is bacteria and nitrate every year, a chemistry panel when the well is new and every few years after, and the aquifer-specific tests (arsenic, radium, barium) at least once.

At a glance

Water test for a new wellRequired

A permit from the county health department (or IDPH where the county has no delegated program) is required before a private well is drilled, the well must be built by an IDPH licensed water well contractor to the Illinois Water Well Construction Code (steel or approved plastic casing, grout, the setbacks from septic systems and other sources, a sanitary well cap above grade), and the contractor files a well construction report with IDPH. Under the code the new well is disinfected and a bacteria sample is collected, in most counties by the health department at the final inspection, before the well is approved for use; the health department's sign-off is what the building department wants before occupancy.

Water test when a home is soldNot required statewide

No statewide requirement. The Illinois Residential Real Property Disclosure Report asks the seller about the water supply and any known defects, and FHA, VA and USDA loans require a bacteria, nitrate and lead sample from a certified lab before closing. A few counties run point-of-sale well and septic inspection programs under local ordinance, so ask the county health department.

What the state recommends

IDPH recommends testing a private well every year for coliform bacteria and nitrate, after any repair or flooding, and whenever the taste, color or smell changes; a chemistry panel (arsenic, iron, manganese, hardness, chloride, sulfate) when the well is new or every few years; and, depending on the aquifer, radium and barium for deep sandstone wells in northern Illinois, arsenic for wells in the Mahomet and other glacial aquifers of central Illinois, and pesticides and nitrate for shallow wells in farm country. County health department labs run the bacteria test cheaply, and the IDPH state lab tests samples submitted through the county.

Free or low-cost testingAvailable

No statewide free program. Most county health departments sell a bacteria (and often nitrate) sample kit for a small fee and explain the result, and the IDPH Division of Laboratories runs the bacteria test for counties without their own lab. The Illinois State Water Survey and university extension programs run periodic free nitrate and arsenic screening clinics in farm counties.

What the water is like

Illinois wells draw from three very different sources. Across the glaciated north and center, most wells are finished in sand and gravel buried in the drift, 50 to 250 feet down; the water is very hard, high in iron and manganese, and in the Mahomet aquifer of central Illinois and parts of the northeast it carries naturally occurring arsenic, with about one well in ten over the standard and no taste to warn you. Deep wells in the Chicago collar counties and the northern tier reach the Cambrian-Ordovician sandstone, which is reliable but brings radium and barium above the standards in many places. Southern Illinois has thin drift and tight bedrock, so wells are shallow, low-yielding and often large-diameter bored wells that fail bacteria tests; sulfur and methane turn up in the coal counties, and deep wells hit natural brine. Shallow wells anywhere in farm country pick up nitrate and atrazine in wet springs, and road salt is pushing chloride up in wells near the Chicago interstates.

Certified labs and the county health departments

Illinois splits the accreditation: IDPH certifies the microbiology labs and the Illinois EPA accredits the chemistry labs, and four county health departments (DuPage, Lake, McHenry and Will) run their own certified labs that sell kits at the counter. Most other counties sell a bacteria kit and send it to the IDPH Division of Laboratories in Springfield. The commercial labs below hold IDPH microbiology certification, Illinois EPA chemistry accreditation, or both, from the state lists of December 2025.

31 certified labs

See all 31 certified labs in Illinois

Licensed water well and pump installation contractors

Illinois licenses the person, not the company: a water well contractor license (for drilling, modifying and sealing wells), a pump installation contractor license, or the combined license, and the licensee has to be on site or supervising. Every profile below is built from the IDPH contractor search as of September 2026, with the licensees at each business address grouped together and every license number shown. Where the ISGS ILWATER records list wells under a licensee’s name, the profile shows how many wells they have drilled since 2016, the counties they work in and the typical depth and yield. A few dozen of the licensees are based in Iowa, Indiana, Wisconsin and Missouri and work across the line.

277 licensed contractors

Anton Rosc

Verified license

Freeport, IL · Stephenson County

License 101-814119 Active

  • Pump Installation
  • Pump Repair

See all 277 licensed contractors in Illinois

By county

Well use runs from almost none in Cook County to a quarter of homes in McHenry and Kendall and four in ten in Cumberland, Mason, Pulaski and Shelby. Each county page carries its well population, the typical depth of private wells on the ILWATER map, the nearest certified labs and the licensed contractors based there.

Illinois well water questions

Do I need a permit to drill a well in Illinois?

Yes. Apply to your county health department (or IDPH in a county without a delegated program) before drilling; the permit checks the site against the setbacks from septic systems, property lines and other sources, and the well is inspected and sampled before it is approved for use. The contractor must hold an IDPH water well contractor license.

Is a water test required when I sell my house?

Not by the state. The seller’s disclosure covers the water supply, government-backed mortgages require a bacteria, nitrate and lead test, and a handful of counties have point-of-sale inspection ordinances, so check with the county health department.

How do I find the record for my well?

Open the ISGS ILWATER map and search by address or zoom to the property. Records for wells drilled since the 1960s show the driller, depth, casing, the formations passed through and the tested yield; the county health department also keeps the permit file.

Where do I get a bacteria test?

From your county health department. Most sell a sample bottle for a small fee, either testing it in their own certified lab or sending it to the IDPH Division of Laboratories, and the environmental health staff will explain the result and what to do about a positive.

My well has arsenic, radium or iron. Can it be fixed?

Yes. Arsenic is handled by a point-of-use reverse osmosis unit for drinking water or a whole-house adsorption system; radium by a water softener or reverse osmosis; iron and manganese by an oxidizing filter or softener. Test again after installation and yearly to confirm the system is keeping up, and have a licensed pump installation contractor do any work on the pump or pressure system.