What to Test Your Well Water For (and How Often)

EPA and CDC both recommend annual testing for these basic contaminants on every private well, regardless of location:

• Total coliform bacteria — indicator organisms for bacterial contamination. Positive means surface water or sewage may be entering the well. EPA MCL: 0 (none allowed).
• E. coli — specific marker for fecal contamination. Positive is an immediate health hazard.
• Nitrate (as nitrogen) — primarily from agricultural runoff (fertilizer, animal waste) and septic systems. EPA MCL: 10 mg/L. Causes "blue baby syndrome" (methemoglobinemia) in infants.
• pH — measure of water acidity. Outside the 6.5-8.5 range can indicate contamination or cause corrosion of pipes.
• Total dissolved solids (TDS) — measure of overall mineral content. Spikes can indicate contamination.

Cost for a basic annual test: $30-$80. Some county health departments offer free or low-cost basic testing. Always use a certified drinking water lab — not a free test kit from a water treatment salesperson.

Every 2-3 years (or more often if conditions change), test for additional contaminants:

• Lead — from older plumbing solder, pipe fittings, or natural sources. EPA action level: 15 ppb. Permanently harmful to children's neurodevelopment.
• Copper — from copper plumbing. EPA action level: 1.3 mg/L. Causes nausea and gastrointestinal symptoms in high doses.
• Manganese — natural deposits, especially in upper Midwest. Causes brown staining, neurological effects in high doses. EPA secondary standard: 0.05 mg/L.
• Iron — natural, causes orange/rust staining and metallic taste. EPA secondary standard: 0.3 mg/L.
• Sodium — natural or from water softeners. Health concern only for sodium-restricted diets.
• Sulfate — natural, causes bitter taste and laxative effect at high levels. EPA secondary standard: 250 mg/L.
• Hardness (calcium and magnesium) — not a health concern but affects soap effectiveness, scale buildup, and appliance lifespan.
• Total alkalinity — buffering capacity of water; affects corrosivity.

Cost for comprehensive panel: $150-$350.

Some contaminants are geographically concentrated. Test for these if you live in an affected area:

• Arsenic — natural in groundwater of New England, upper Midwest, parts of the Southwest, and Pacific Northwest. EPA MCL: 10 ppb. Causes cancer and cardiovascular disease at chronic low-level exposure.
• Radon — radioactive gas from granite bedrock. Common in New Hampshire, Pennsylvania, parts of New York, Idaho, and the Carolinas. No federal MCL but EPA proposed alternative MCLs of 300-4,000 pCi/L.
• Uranium — natural in granite areas, especially New Mexico, Colorado, and parts of New England. EPA MCL: 30 ppb.
• Methane — near oil/gas drilling, especially fracking operations in Pennsylvania, West Virginia, Texas, and Colorado. No federal MCL but levels above 10 mg/L are explosive.
• VOCs (volatile organic compounds) — near industrial sites, gas stations, dry cleaners, military bases. Includes benzene, MTBE, TCE, PCE.
• PFAS (per- and polyfluoroalkyl substances) — near military bases, fire training facilities, manufacturing sites. EPA finalized MCLs in 2024: 4 ppt for PFOA and PFOS individually.
• Pesticides — atrazine, glyphosate, chlordane, others — near farms, nurseries, golf courses. Various EPA MCLs.

Your state environmental department typically publishes contamination maps showing which areas have known issues. Check before deciding which tests to run.

Get an immediate test if any of these occur:

• Visible change in water: color (red, brown, yellow, cloudy), sediment, oily film
• Change in taste or smell: metallic, sulfur (rotten eggs), chlorine, chemical, sweet
• Family member illness: repeated GI symptoms in household members may indicate bacterial contamination
• Nearby well construction or repair: can stir up sediment or introduce bacteria
• Flooding or heavy rain: surface contamination can enter shallow wells
• New industrial or agricultural activity nearby: within 1-2 miles
• Septic system failure or major repair on your property or upslope
• Pregnancy in the household: nitrates and bacteria are especially concerning for pregnant women and infants
• New baby joining the household: nitrates above 10 mg/L are dangerous for infants under 6 months

The lab provides specific bottles and instructions. General principles:

1. Use the bottles provided by the lab. Don't reuse bottles or use household containers — they may have residues that contaminate the sample.
2. Sample from the cold tap closest to the well, before any treatment system. Usually a kitchen tap or basement tap.
3. Run the water for 5-10 minutes before collecting the sample. This flushes the pipes and gives a sample of actual well water, not water that's been sitting in pipes.
4. For bacterial testing: sterilize the tap with a flame or alcohol, let cool, then collect. Don't touch the inside of the bottle.
5. For chemical testing: fill to the line, no air gap if specified.
6. Refrigerate immediately if not delivering same-day. Bacterial samples must be analyzed within 24-48 hours.
7. Deliver promptly with the chain-of-custody form filled out.

Improper sampling is the most common reason for false positive bacterial results. If you get an unexpected positive, retest with a fresh sample and proper technique before assuming you have contamination.