What does ND on my lab report mean?

Not detected: the analyte, if present at all, sits below the lab’s reporting limit for that method. It is the best possible line on a report. It does not mean zero molecules, it means below the level the method can reliably measure, which for drinking water purposes is the answer you want.

Is any detection a reason to buy treatment?

No. A detection below the Maine guideline, like uranium at 6 ug/L against a 30 ug/L guideline, is information, not a purchase order. It earns a spot in your records and maybe a shorter retest interval if it sits near the line. Treatment decisions follow confirmed exceedances, not the mere presence of an analyte.

Why retest before buying a system?

Because a single sample can mislead, and treatment is sized and chosen against the number. Bedrock well chemistry varies, sampling technique matters, and a marginal result can land on either side of the guideline twice in a row. A second sample that agrees turns a data point into a fact worth spending thousands of dollars on.

What if several things exceed at once?

Common in Maine bedrock country: arsenic plus radon, or iron plus bacteria. Combined problems change system design, since stages interact, so bring the whole report to one professional rather than solving line by line with separate gadgets. The whole-house treatment page explains how stages get sequenced.

How to read a Maine well water test report

A Maine lab report packs a lot of chemistry onto one page: abbreviations, three different units, and a column of guideline values that decides everything. This guide reads that page line by line, in the order a Maine well owner actually needs: what the units mean, what the guideline column is, the difference between a detection and an exceedance, which results deserve a second sample before any money moves, and which one result skips the line entirely. If you have not tested yet, start instead at the testing page or the testing recommendations checklist.

The units: ug/L, mg/L, and pCi/L

Three units carry nearly every line. Micrograms per liter (ug/L) measure trace contaminants like arsenic and uranium; one ug/L is one part per billion (ppb). Milligrams per liter (mg/L) measure the common chemistry, nitrate, chloride, fluoride, manganese; one mg/L is one part per million (ppm), which is 1,000 times larger than a ug/L. Picocuries per liter (pCi/L) measure radioactivity and appear on the radon line. The unit mix is the classic misreading trap: manganese at 0.4 mg/L is 400 ug/L, so always compare a result to its guideline in the same unit, and PFAS results arrive in nanograms per liter (ng/L), a thousand times smaller again than ug/L.

The Maine guideline column

Most Maine labs print a guideline or maximum contaminant level beside each result. Federal MCLs legally bind public water systems, not private wells; for well owners, Maine publishes guideline values drawn from those standards and from Maine CDC guidance. The working set, per the Maine Tracking Network: arsenic 10 ug/L, uranium 30 ug/L, nitrate 10 mg/L, manganese 0.3 mg/L, fluoride 2 mg/L, chloride 250 mg/L. Radon in water carries a Maine guideline of 4,000 pCi/L, per Maine CDC. Bacteria lines are pass or fail: the target for total coliform and E. coli is simply absent.

Detection versus exceedance

A detection means the lab found the analyte above its reporting limit (often printed as RL or MRL); ND means it did not. An exceedance means the result is above the guideline value. The distinction is the whole art of staying calm with a lab report in hand: uranium detected at 6 ug/L is a detection and a non-event, uranium at 45 ug/L is an exceedance and a treatment conversation. Detections below the guideline earn a place in your records and nothing more, though a result creeping toward the line is a reason to shorten your retest interval.

A worked example, line by line

Illustrative values, not a real household. Guidelines per the sources above. Your water needs its own test.

Analyte	Result	Guideline	Read
Total coliform	Present	Absent	Act now, see below
E. coli	Absent	Absent	Good, but coliform still needs fixing
Nitrate	1.8 mg/L	10 mg/L	Detection, no action
Arsenic	12 ug/L	10 ug/L	Marginal exceedance, retest then treat
Uranium	6 ug/L	30 ug/L	Detection, record it
Radon (water)	4,600 pCi/L	4,000 pCi/L	Marginal exceedance, retest
Manganese	0.4 mg/L	0.3 mg/L	Exceedance, explains black flecks
Fluoride	0.3 mg/L	2 mg/L	Detection, no action
pH	6.2	No health guideline	Acidic, corrosive tendency, watch for blue-green stains

Which results earn a retest before you spend

Marginal exceedances, the ones sitting just past the line like the arsenic 12 and radon 4,600 above, are retest candidates before any equipment purchase. Bedrock well chemistry moves, sampling conditions matter, and a system gets sized to a number, so you want two samples that agree before committing thousands of dollars. The same logic applies in reverse: a marginal pass close under the guideline is worth rechecking sooner than the standard three-to-five-year cadence. What each system costs once a number is confirmed is laid out in the cost guide, and treatment options by contaminant live on the services pages.

Clear, well-confirmed exceedances, several times the guideline, change the calculus: confirm with a retest, but start treatment conversations in parallel rather than waiting, especially for arsenic over 50 ug/L as covered in the arsenic data page.

The one line that skips the queue: bacteria

Bacteria results are the exception to test-twice-then-decide. A positive E. coli result means stop drinking the water and switch to bottled or boiled water until the well is disinfected and a follow-up sample comes back absent, consistent with Maine CDC well water guidance. A total coliform hit without E. coli, like the worked example, is less acute but still prompt work: inspect the wellhead, disinfect, retest, and if hits keep recurring, look at UV disinfection on the bacteria and UV page. Boiling handles microbes only; it does nothing for arsenic, uranium, or nitrate.

Nitrate deserves its own flag: above 10 mg/L matters most for infants, per the Maine CDC guidance linked above, so households mixing formula act on that line promptly rather than on a retest timeline.

Sampling notes that move numbers

A report describes one sample from one tap on one day, and three sampling details commonly explain odd results. First, raw versus treated: if the house already has treatment, know which side of it the sample came from, since a raw-water sample checks the well and a treated-water sample checks the equipment, and comparing your report to the wrong purpose wastes it. Second, tap and timing: whether the line was flushed before filling the bottle changes what metals from household plumbing end up in the sample, which matters for copper and lead questions more than for bedrock analytes. Third, weather: a bacteria sample collected right after heavy rain or snowmelt describes the well at its most stressed, useful information, but worth noting on the paperwork when comparing to past results. When a number surprises you, check these three before concluding the well changed. Labs and the professionals who sample for a living control all of this by habit, one reason purchase-window tests are often collected by a third party, as covered in the home-buying guide.

Want a second pair of eyes on the report?

Send the basics through the form and we connect you free with an independent local professional who reads Maine well reports every week, and can turn a confirmed exceedance into a sized, priced fix.