Test your well water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level. Contact your health department to find out what other germs or chemicals to test for based on where you live. Use a state-certified laboratory to test your water. Your health department can help you understand your test results and what to do next.
https://www.cdc.gov/drinking-water/safety/guidelines-for-testing-well-water.html