Wisconsin county well guide

Well Water in Rock County, WI: Testing, Contractors and Rules

About 12,196 households in Rock County, 19% of the county, rely on a private well. Nobody tests that water unless the owner does.

Labs within 40 milesLicensed contractors
19%of households on a private well
Share on wells, county vs state
Rock County19%
Wisconsin average28%
37licensed contractors serve the county
5 mito the nearest certified lab, Rock County Health Department Janesville
Nostatewide test required when a home is sold

About one in 5 households in Rock County relies on a private well, around 12,196 homes. Outside the towns with public water, wells are the norm here.

Local rules for wells in Rock County

In Rock County the state, not the county, sets the rules. The DNR licenses every driller and pump installer, requires a notification and fee before a new well, and requires the driller to test it for coliform and nitrate. Selling a home does not trigger a state test, though lenders often ask for one. The state’s recommendations are in the cards below.

At a glance

Water test for a new wellRequired

Under NR 812 the well driller must collect a bacteria (coliform) and nitrate sample from every new well and report the results to DNR; the pump installer collects a bacteria sample after installing or replacing a pump. A well notification form and fee are filed with DNR before drilling.

Water test when a home is soldNot required statewide

No statewide requirement at sale. If a well is inspected for a real-estate transaction, only a licensed well driller or pump installer may perform the paid inspection, and the inspection must include bacteria, nitrate and arsenic tests.

What the state recommends

DNR and DHS recommend testing for coliform bacteria and nitrate every year, arsenic and lead at least every 5 years (arsenic yearly in known areas of the Fox River Valley), fluoride once, and manganese, PFAS or radium where local conditions warrant. Test any time taste, color or odor changes or after flooding.

Free or low-cost testingAvailable

Some county health departments and UW Extension programs run subsidized nitrate and bacteria screening clinics; check the county health department. The DNR-certified lab list shows which labs accept homeowner samples.

Getting your water tested near Rock County

The nearest certified lab is Rock County Health Department Janesville in Janesville, about 5 miles from the county center, and it accepts samples from homeowners. There are 5 more within 40 miles, listed below with what each tests for.

6 certified labs within 40 miles

Licensed well contractors serving Rock County

Licensed help in Rock County includes Absolute Pump & Well Service LLC and Aqua Well & Pump Systems Inc and 33 others. Every listing was matched to the Wisconsin license list; the “verify” link on each profile opens the state lookup.

Well depth and water chemistry

Well depth and water chemistry in Rock County follow the rock underneath it. Depth varies across the county; the state well record search shows logs for nearby wells.

Typical well depth

Varies by location. Check the state well record search for logs of nearby wells.

Contaminants to test for
  • Coliform bacteria
  • Nitrate
  • Arsenic (Fox River Valley
  • St. Peter sandstone)
  • Manganese
  • Iron
  • Hardness
  • Strontium (eastern counties)
  • Radium (eastern deep sandstone aquifer)
  • PFAS (Marinette
  • Peshtigo
  • Dane County areas)
  • Lead

Neighboring counties: Walworth County, Green County, Jefferson County, Dane County.

What well work costs in Rock County

Basic bacteria and nitrate test$25 to $75lab fee, homeowner sample
Full panel lab test$150 to $400metals, VOCs, radiologicals
Well inspection$250 to $550flow, pressure, visual, water test
Submersible pump replacement$1,200 to $4,500parts and labor
Pressure tank replacement$400 to $1,200installed
Whole-house treatment system$800 to $6,000softener, iron filter, UV, RO
New well drilled$5,500 to $25,000about $25 to $65 per foot
Shock chlorination$80 to $300or about $20 as a DIY job

National ranges from published 2025 to 2026 contractor pricing. Local quotes vary with depth, access and materials.

Questions Rock County well owners ask

How many homes in Rock County are on a well?

About 12,196, or 19% of households, based on Census housing data and state well surveys. The share is highest outside the towns with public water.

Where is the closest certified lab to Rock County?

Rock County Health Department Janesville in Janesville, about 5 miles away. It accepts homeowner samples.

Do I need a permit to drill a well in Rock County?

A well notification and fee must be filed with the Wisconsin DNR before drilling, and only a DNR-licensed well driller may drill it. Some counties add their own permit or setback review, so check with the county land conservation or zoning office.

What does a well test cost near Rock County?

A bacteria and nitrate test runs $25 to $75 at most certified labs; a full panel with metals is $150 to $400. Several county health departments and the state lab of hygiene sell homeowner kits for bacteria and nitrate at low cost; ask the county about screening clinics.