Well water testing without the guesswork.
About 43 million Americans get their drinking water from a private well, and none of it is checked by the EPA. Here's the split every well owner should run: routine on-site spectral screening for the minerals and organics that shift week to week, plus an annual certified lab panel for the microbial and heavy-metal contaminants that don't forgive a wrong answer.
Two tests, two jobs
Private well water changes with the seasons. Spring runoff pushes nitrate up. Summer drawdown concentrates iron and hardness. A new septic field two houses over can introduce coliform overnight. Testing once a year misses all of it.
The working split is simple:
- On-site spectral screening — pH, hardness, TDS, iron, residual chlorine, and organic load. Fast, repeatable, monthly. Catches drift.
- Annual certified lab panel — coliform, E. coli, arsenic, lead, nitrate confirmation, uranium, radon in the regions that need it. Slow, expensive, decisive. Confirms safety.
What to scan every month
pH and hardness
Well pH usually sits 6.0–8.5 depending on aquifer geology. A steady drop below 6.5 is a signal to pull a corrosion sample — acidic water leaches copper and lead from household plumbing. Hardness above 180 mg/L (10.5 grains) is what your softener is supposed to reduce; a rising post-softener reading means the resin is exhausted.
TDS and iron
TDS drift tells you the aquifer is either recharging (dropping) or concentrating (rising). Iron above 0.3 mg/L stains fixtures orange and clogs aerators; above 1 mg/L it's a taste problem. Both parameters shift on a monthly timescale — perfect for on-site testing, wasteful to mail to a lab.
Nitrate and organics
Nitrate is the fastest-moving well contaminant in agricultural regions. The drinking-water limit is 10 mg/L as N; infant safety cutoffs are lower. A monthly screening for nitrate plus organic load catches runoff events before an annual lab test would.
What to send to a lab every year
Total coliform and E. coli
The single most important annual test. Any detect is a fail — shock-chlorinate the well, retest, and if it persists, inspect the wellhead seal and casing. Coliform is microbial; there is no reliable at-home spectral method for it.
Heavy metals
Arsenic, lead, copper, and — in specific geologies — uranium. These matter at parts-per-billion levels and require ICP-MS analysis. Budget $50–$150 for the panel; do not skip.
Radon (regional)
If your county sits on granite bedrock or a known uranium belt, add a radon-in-water test. The proposed EPA MCL is 4,000 pCi/L; anything above that changes what treatment you need.
A monthly well water routine
- Sample cold, not hot. Hot-water lines pick up sediment from the heater and bias iron and hardness readings.
- Flush for two minutes. Stagnant water in the plumbing is not representative of the aquifer.
- Run one spectral scan. pH, hardness, TDS, iron, chlorine, and organics in one five-second read.
- Log the reading. The point isn't the absolute number; it's the trend line. A monthly log surfaces problems long before a taste or color change does.
- Escalate on drift. Two consecutive months of movement outside your baseline is when to schedule an off-cycle lab panel.
Frequently asked questions
How often should I test my well water?+
Run an on-site check for pH, hardness, TDS, iron, and nitrate every month during heavy use season. Send a sample to an EPA-certified lab once a year for a full microbial and heavy-metals panel — coliform, E. coli, arsenic, lead, uranium, and radon where applicable.
What contaminants are most common in private well water?+
The most frequently flagged issues in US private wells are coliform bacteria, nitrate from agricultural runoff, iron and manganese staining, arsenic in specific geologies, and hardness from limestone aquifers. None of these are visible; all are testable.
Can a spectral sensor replace a lab test?+
No — and that's not what it's for. A spectral sensor like Vispect PureFlow gives you a five-second read of pH, hardness, TDS, residual chlorine (for shock-treated wells), iron, and organic load. It catches drift between annual lab panels so a change gets flagged in days, not months. Microbial safety still requires a certified lab.
What is a routine well water screening?+
A routine screening measures the parameters that shift with weather, pumping, and seasonal recharge: pH, hardness, TDS, iron, nitrate. These are the numbers that tell you whether your softener or filter is still doing its job — check them monthly on-site.
When should I retest after a change?+
Retest immediately after any flooding, nearby construction, a new septic install within 100 ft, a change in taste or color, or any plumbing work on the well head or pressure tank. One clean historical reading does not carry forward through a disturbance.
Do I need to disinfect the tap before sampling?+
For a spectral scan, no — sample straight from a cold tap after a two-minute flush. For a microbial lab kit, follow the lab's disinfection instructions exactly: flame or bleach the spigot, run the tap five minutes, then fill the sterile vial without touching the rim.
Related guides
The four methods that matter — strips, TDS pens, lab panels, and spectral scans — compared side-by-side.
The phenolic chemistry behind color, structure, and aging — and how to measure it from one drop.
When to trust a spectral sensor and when to send samples to ETS or a certified lab.