Well water testing checklist

Private well owners are responsible for their own testing. Here's what the Wisconsin DNR recommends.

Test	How often	WSLH price*
Bacteria (total coliform / E. coli)	Every year, and whenever taste, color or smell changes	$35
Nitrate	Every year, and before use by someone who is or may become pregnant, or for an infant	$35
Arsenic	Every 5 years for most wells; every year in Outagamie, Winnebago or Brown counties, or after a previous arsenic result	$38
Homeowner package (bacteria, nitrate, metals, hardness, VOCs, atrazine)	Optional, when buying a home or troubleshooting	$450

*Wisconsin State Laboratory of Hygiene price list, checked Nov 5, 2026. Other certified labs and county health departments may charge less or more.

When results come back

Bacteria present: stop drinking the water (DNR).
Nitrate over 10 mg/L: don't give it to infants under 6 months or use it for formula, and avoid it if pregnant (DNR).
Arsenic over 10 µg/L: DHS recommends not using it for cooking foods that absorb a lot of water.
Get the sample to the lab within 48 hours, and follow the kit's directions to avoid false positives.

Official links

Private well owners are responsible for their own water quality. Public water systems are regulated; most private wells are not sampled for you automatically.
Wisconsin DNR recommends yearly bacteria and nitrate tests for private wells, with arsenic on a longer cycle for many wells (and more often in some counties or after a prior detect).
If bacteria are present, stop drinking the water until you follow your health department or DNR guidance. Nitrate above 10 mg/L is a special concern for infants and pregnancy — follow DNR / DHS advice, not this checklist alone.
At-home strip kits can be a screen only. Confirmatory results should come from a certified lab using the kit instructions (including delivery time limits).

Sources linked above under Official links (WI DNR and WSLH).