What to test your well water for
Last reviewed:
State recommendations differ, so check your county page for local contaminants. Here's what the agencies we've reviewed recommend.
Baseline: every year
- Total coliform bacteria / E. coli. Recommended yearly by PA DEP, NHDES and Wake County, NC[1][2][3].
- Nitrate (and nitrite). Yearly per PA DEP and NHDES[1][2]. Penn State says nitrate can be elevated near intensive agriculture or dense or failing septic systems[4].
- pH and total dissolved solids. PA DEP: yearly. Penn State: every three years[1][4].
Every 3-5 years: a full panel
NHDES's list for private wells covers arsenic, bacteria, chloride, copper and lead (stagnant and flushed), fluoride, hardness, iron, manganese, nitrate, nitrite, pH, radon, sodium, uranium and four PFAS compounds. It recommends retesting everything except bacteria, nitrate and nitrite every 3-5 years[2]. Wake County recommends a "First Timer's Package" (bacteria, inorganics, VOCs, pesticides) if you've never tested or your last test was more than five years ago[3].
Add these when your geology or surroundings call for it
| Test | When it matters |
|---|---|
| Arsenic | Naturally occurring in some bedrock. In NH state-lab data, 25% of wells tested statewide exceeded 5 µg/L[5]. |
| Radon, uranium, gross alpha | Naturally occurring radioactivity in some rock types, such as NH bedrock, parts of eastern Wake County, NC, and quartzite areas of Chester County, PA[5][6][7]. |
| Lead and copper | Mostly from plumbing. Use a first-draw sample. Penn State says corrosive (low-pH) water makes this worse[4]. |
| VOCs (gasoline, solvents) | Near fuel spills, industry or landfills. NHDES notes MtBE can show up even in remote areas[8]. |
| PFAS | NHDES recommends all private well owners test for PFAS and notes it can be costly[2][9]. |
| Pesticides / herbicides | Near farm fields or past foundation treatments. NHDES does not recommend routine pesticide testing because of cost, unless nitrate is elevated or pesticides were applied near the well[3][8]. |
| Barium, chloride | Near gas or oil drilling. Penn State has a drilling package. Chloride also comes from road salt[4]. |
| Iron, manganese, hardness | Staining, taste, scale. Useful before you buy a softener or filter[3][4]. |
Also test when...
...you buy a home with a well, you install or service treatment, the water's taste, smell or color changes, or after a flood or well repair[2][10].
Sources
- PA DEP - Private Wells: Water Testing
- NHDES - Water Testing Guidance for Private Well Users (April 2026)
- Wake County, NC - Available Well Water Tests and Fees
- Penn State AASL - Drinking Water Testing
- NHDES (Kernen) - Private Wells in Portsmouth, 2021
- Wake County - Naturally Occurring Contamination
- USGS SIR 2010-5087 - Chester County groundwater quality
- NHDES DWGB-2-1 - Suggested Water Quality Testing for Private Wells (2020)
- NHDES PFAS - Private Wells
- BSC Labs - Testing Your Water