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Wisconsin has very high private well usage, with a substantial portion of households relying on private wells. The state's varied geology-from the Driftless Area to the glacial till of central and northern Wisconsin-creates different groundwater conditions across regions.
Wisconsin does not have a statewide mandate requiring private well water testing for all existing well property sales. However, testing is required for new well construction and for property sales involving certain programs. The state takes an active educational approach.
Known contaminants of concern include nitrates (particularly in agricultural areas), naturally occurring arsenic in some regions, and bacteria. Wisconsin DNR and county health departments provide guidance and resources for well owners.
Wisconsin requires water testing for new well construction before the well can be approved for use. Testing must include bacteria and nitrate at minimum.
For property sales, testing is not universally mandated by state law. However, FHA, VA, and certain other mortgage programs require water testing. Many lenders require testing regardless of loan type.
Wisconsin strongly recommends annual testing for all private well owners. The DNR and county health departments provide educational resources and testing guidance.
Real estate transactions often include testing even when not legally required. Many buyers request testing during due diligence.
Wisconsin DNR recommends annual testing for bacteria and nitrates as a minimum. These are the most common concerns and provide essential safety information.
Nitrates are a particular concern in Wisconsin due to agricultural activity. The state has significant areas where nitrate contamination of groundwater is a known issue. Nitrates are especially dangerous for infants.
Arsenic occurs naturally in some Wisconsin groundwater formations. It's odorless and tasteless, so testing is the only way to detect it. Some counties have higher arsenic occurrence than others.
Consider testing for: lead (especially with older plumbing), pH, and any contaminants your county health department identifies as concerns for your area.
Required for new well approval
Every year
At least once, repeat every 3-5 years
Well water testing costs in Wisconsin depend on what you're testing for. Basic bacteria and nitrate tests are affordable. Adding arsenic or comprehensive panels increases the cost.
Wisconsin has many certified laboratories serving well owners. County health departments may offer testing or referrals. UW-Extension provides educational resources. The Wisconsin State Laboratory of Hygiene is a key resource.
Turnaround time follows typical patterns: bacteria results within a few days (samples are time-sensitive), chemical tests within 5-10 business days.
For new well construction, testing must be completed before well approval. For real estate transactions, plan ahead to allow adequate time.
Wisconsin well owners can choose from certified laboratories, county health department programs, the State Laboratory of Hygiene, and mail-in test kit providers. For accurate, defensible results, use DNR-certified labs.
The Wisconsin State Laboratory of Hygiene offers testing services at competitive rates and is a reliable resource for well owners.
County health departments are valuable local resources. They may offer testing, maintain lists of certified labs, and understand groundwater issues specific to your county.
Given regional variation-arsenic in some areas, nitrates in agricultural regions-local knowledge matters. Your county can advise on priority concerns.
Quick answers to common questions about testing well water in Wisconsin, from requirements to regional concerns.