Private wells should be tested at least once a year for bacteria like total coliform and E. coli. You should also test every two to three years for nitrates, metals, and other common contaminants. If you notice any change in taste, color, or odor — or after floods, repairs, or drought — test immediately. Regular testing helps catch small issues before they become serious and ensures your water remains safe year-round.

Most states require well water testing when selling a home with a private well. The standard panel usually includes bacteria, nitrates, and sometimes arsenic or lead, depending on local laws. These results must be shared with buyers before closing. Even if not legally required, it’s smart to test voluntarily — it protects both seller and buyer by confirming that the property’s water source is safe and compliant with local health standards.

Bacterial contamination usually happens when surface water or soil bacteria enter the well system. Common causes include a cracked casing, a loose or damaged well cap, improper sealing, or floodwater pooling near the wellhead. Septic systems located too close to wells can also leak bacteria into groundwater. Regular inspections, a properly sealed cap, and good surface drainage are the best defenses against bacterial intrusion.