Seasonal Well Testing: When in the Year to Test
Spring
Snowmelt and spring rain can carry surface water and bacteria into poorly sealed wells. Many health departments suggest testing in spring. See our snowmelt flood watch.
Summer
USGS has reported that drought can raise naturally occurring arsenic in some private wells, as water levels drop. If you had a dry spell and arsenic is a concern locally, consider a retest.
Fall
Fertilizer and manure applications can affect nitrate in shallow wells near fields. USGS links higher nitrate in groundwater to farmland. A fall nitrate test helps if you're near crops.
Winter
Road salt can raise chloride and sodium in wells close to roads. A USGS and Vermont Department of Health study found wells within 100 meters of a paved road had significantly higher chloride.
Any time
After floods, well work, or a change in the water, test right away. Check flood alerts.
Sources
- EPA: Protect your home's water
- USGS: Drought may lead to elevated arsenic in private wells
- USGS: Nitrogen and water
- USGS: Chloride in domestic wells and proximity to roads, Vermont 2011–2018
- EPA: What to do with your private well after a flood
Questions
What is the best month to test well water?
There's no single best month. Spring after snowmelt is common, but the most important thing is to test every year at about the same time, and after floods or changes.
Free well water safety checklist
15 family-friendly steps based on CDC and EPA guidance. Print it, keep it on the fridge, and know when to call a certified lab.
More guides
- Flood Protection for Well Owners: Before, During and After a FloodRaise and seal the wellhead, know your pump shutoff, then disinfect and test with a certified lab after any flood.
- PFAS “Forever Chemicals” in Private Wells: Why You Should TestFederal PFAS rules protect public water systems — not private wells. Here’s what “forever chemicals” mean for well owners and how to get tested.
- Nitrates in Well Water and Blue Baby Syndrome: Who Must TestNitrate in well water can cause blue baby syndrome in infants. Learn who is at risk, when to test, and how to find a certified lab.
- Arsenic in Private Well Water: The Invisible Risk UndergroundArsenic in groundwater is often naturally occurring and invisible. USGS research shows millions of private-well users may be above the EPA drinking-water standard.