What to test well water for: the annual panel, the units, and what each result decides

Short answer

A private well test panel starts with the four tests CDC and EPA both list for every year: total coliform bacteria, nitrate, total dissolved solids (TDS) and pH, run by a state-certified laboratory. Two of those carry enforceable EPA limits: nitrate at 10 mg/L measured as nitrogen, and coliform under the Total Coliform Rule. TDS and pH have only EPA secondary standards, 500 mg/L and 6.5 to 8.5, which EPA does not enforce. Symptom tests are added on top of the four: iron (secondary standard 0.3 mg/L) for rust stains, manganese (0.05 mg/L) for black stains, hardness in grains per gallon for scale, sulfate (250 mg/L) for an off or bitter taste, hydrogen sulfide on site for rotten-egg odor, and a first-draw lead and copper sample read against EPA’s action levels of 0.015 mg/L and 1.3 mg/L. The Minnesota Department of Health adds arsenic, lead and manganese at least once in the life of the well.

A test strip cannot clear a well for a house with a newborn or a pregnancy: CDC lists both as testing triggers and names a state-certified laboratory, not a kit, so if that is your household this is the lab page, not the strip aisle.

Which four tests does every well need every year?

CDC and EPA give the same annual list, in the same words: total coliform bacteria, nitrates, total dissolved solids and pH, at least once every year, at a certified lab. Everything else on this page is added to that list, never substituted for it.

A maximum contaminant level (MCL) is an enforceable EPA limit for public water systems. A secondary standard is EPA’s non-mandatory guideline for taste, odor, color and staining. A private well is regulated by neither; both serve here as the reference lines the lab report is read against.

Test	Unit	Limit	Who sets it	What a high result decides
Total coliform bacteria	Positive or negative per sample	For public systems, no more than 5.0% of samples positive in a month; a single well sample is read as present or absent	EPA, Total Coliform Rule (enforceable MCL)	Disinfect the well and water system, then test again (Minnesota Department of Health)
Nitrate	mg/L as nitrogen	10 mg/L	EPA MCL, enforceable	Contact the local health department; a nitrate treatment page is planned, not yet written
Nitrite	mg/L as nitrogen	1 mg/L	EPA MCL, enforceable	Same route as nitrate
Total dissolved solids (TDS)	mg/L	500 mg/L	EPA secondary standard, not enforced	Ask the lab which ions make up the total: hardness and sulfate each have a row in the symptom table below; chloride has its own EPA secondary standard of 250 mg/L
pH	pH units	6.5 to 8.5	EPA secondary standard, not enforced	Below 6.5, add the first-draw lead and copper sample in the plumbing section; a neutralizer page is planned

The interval is the one documented disagreement. Penn State Extension keeps coliform annual but tests pH, TDS and other locally relevant contaminants every three years, and adds a professional system inspection at least every ten years. The method is the same across all three sources; only the pH and TDS interval differs.

Which symptom sends you to which extra test?

Each row adds one line to the certified-lab order and names the page that reads the result. Iron, manganese, sulfate and hardness are mailed to the lab with the annual four. Hydrogen sulfide is the exception, and its row says why.

Symptom	Add this test	Unit	Limit and who sets it	What the result sends you to
Orange or rust rings in the toilet, tub, sink	Iron	mg/L	0.3 mg/L, EPA secondary standard	Iron in well water: form, mg/L range and treatment class
Black or dark brown stains, bitter metallic taste	Manganese	mg/L	0.05 mg/L, EPA secondary standard	The same iron guide, which folds manganese into its treatment table
Rotten-egg odor at the tap, worse on hot water	Hydrogen sulfide, tested on site	mg/L	No EPA limit; University of Georgia Extension says it escapes water too quickly for a mailed lab sample	Rotten egg smell in well water: source, anode rod, treatment class
White crust on fixtures, spotted glassware, scale in the kettle	Hardness	grains per gallon (gpg)	No EPA limit for hardness itself; the adjacent secondary standard is TDS at 500 mg/L	Hard water and white scale, then the softener size calculator
Off or bitter taste, especially with high TDS	Sulfate	mg/L	250 mg/L, EPA secondary standard; University of Georgia Extension says levels above it require treatment before use	A sulfate and reverse-osmosis page is planned, not yet written
Blue-green stains, metallic taste, or pH under 6.5	Copper and lead, first draw	mg/L (lead often reported in ug/L)	Copper 1.3 mg/L and lead 0.015 mg/L, EPA Lead and Copper Rule action levels	The lead and copper section below

Beyond symptoms, EPA’s Protect Your Home’s Water page carries a chart matching household conditions and nearby land use to added tests, from recurring illness to nearby farms, fuel stations and dry cleaners. Read it before ordering: the lab prices each added line separately.

Do I need to test for lead and copper, and how?

At least once, yes. The Minnesota Department of Health names five common well contaminants: nitrate and coliform bacteria every year, and arsenic, lead and manganese at least once. MDH reports arsenic in about half of the private wells constructed there since 2008, which is why arsenic is on the once-in-a-well’s-life list even without a symptom.

Lead and copper are different from every other line on the panel because they usually come from the house, not the aquifer. That is why the sample is taken differently.

A first-draw sample is the first water out of a tap after it has stood in the plumbing for hours. Connecticut DPH’s protocol: at least six hours motionless, the cold tap, the aerator removed, and no running the water before you fill the bottle.

The reference lines are EPA’s Lead and Copper Rule action levels: lead 0.015 mg/L (15 ug/L), also Connecticut’s private-well threshold, and copper 1.3 mg/L. EPA’s lead action level drops to 0.010 mg/L on November 1, 2027, the Lead and Copper Rule Improvements compliance date.

Copper also carries a separate EPA secondary standard of 1.0 mg/L for taste and staining, below the 1.3 mg/L action level.

The pair of samples tells you where the metal is. Connecticut DPH’s reading: a first draw well above a flushed sample means corrosion of household plumbing, and similar levels in both mean the well or pump. Low pH on the annual panel is the usual reason plumbing corrodes, so a pH result under 6.5 is what triggers this section.

Certified lab or test strip: which does the panel need?

The panel needs the lab. CDC says use a state-certified laboratory; EPA says use only certified drinking-water laboratories; Minnesota’s health department accredits labs so their methods give accurate results, and tells owners to contact one for containers and instructions.

A strip has two honest jobs. It screens a symptom so you know which lines to add before paying for them, and it is the field test for hydrogen sulfide, which the University of Georgia Extension says escapes water so quickly that a laboratory result is very difficult to obtain after shipment.

Rule	Applies to	Why
Use the sterile bottle the lab supplies, do not rinse it	Coliform	The lab’s container and instructions are the method (Minnesota Department of Health)
First draw only: six hours stagnant, cold tap, aerator off, no pre-run	Lead and copper	Connecticut DPH’s protocol; a flushed sample measures the source instead of the pipes
Test at the tap, on site	Hydrogen sulfide	It off-gasses before a mailed sample reaches the lab (University of Georgia Extension)
Normal draw per the lab’s instructions	Nitrate, TDS, pH, iron, manganese, hardness, sulfate, arsenic	These are stable in the bottle; the lab’s sheet sets any hold time

Before you buy anything

Do not buy a softener, iron filter or neutralizer on the strength of a stain or a strip. The lab panel decides that: the annual four at a state-certified laboratory, plus the symptom lines above, and a first-draw lead and copper pair if pH is under 6.5. Contact an accredited lab for containers and instructions, then match the report to the guide each row points at.

How often after the first year?

Coliform and nitrate stay annual in every source cited here: CDC, EPA and the Minnesota Department of Health. Arsenic, lead and manganese are at-least-once tests per MDH; Penn State puts pH and TDS on a three-year cycle where CDC and EPA keep them annual.

Between scheduled tests, CDC’s triggers restart the clock: a notice of well problems in the area, flooding or land disturbance near the well, repair or replacement of a well component, a change in taste, color or smell, a pregnancy, or a child moving into the household.

MDH adds a retest after disinfecting the well and water system, so a positive coliform result is always two tests, not one.

Order the annual four (coliform, nitrate, TDS, pH) from a state-certified lab and ask for its sample instructions.
Add the symptom lines from the table: iron, manganese, hardness, sulfate, and a first-draw lead and copper pair if pH is under 6.5 or the well has never had one.
Test hydrogen sulfide at the tap the day the other bottles go out.
Read each result against the limit in its row, then open the guide the row points at.
Retest after any well work, disinfection or symptom change, and put coliform and nitrate on next year’s calendar.

Frequently asked questions

How often should I test my well water?

CDC and EPA both say at least once every year for total coliform bacteria, nitrate, total dissolved solids and pH, at a state-certified laboratory. Penn State Extension keeps coliform annual but moves pH and TDS to every three years. The Minnesota Department of Health adds arsenic, lead and manganese at least once, and a retest after any well disinfection.

What is the EPA limit for nitrate in well water?

EPA's maximum contaminant level for nitrate is 10 mg/L measured as nitrogen, and it is an enforceable standard under the National Primary Drinking Water Regulations. Nitrite has a separate enforceable limit of 1 mg/L as nitrogen. Read the lab report's unit carefully, because a result reported as nitrate rather than as nitrogen is not on the same scale.

Do I need a certified lab or is a test strip enough?

For the annual four and for the metals, CDC's instruction is to use a state-certified laboratory, EPA's is to use only laboratories certified for drinking water testing, and the Minnesota Department of Health accredits labs specifically so methods and standards give accurate results. A strip is a screening step before paying for a panel. The one test done on site rather than mailed is hydrogen sulfide.

How do I test for lead and copper in a private well?

Connecticut DPH's protocol is a first-draw sample: water that has sat motionless in the plumbing for at least six hours, from the cold tap with the aerator removed, with no running before you collect. Compare against EPA's action levels of 0.015 mg/L for lead and 1.3 mg/L for copper. A first draw far above a flushed sample points at household plumbing, not the well.

Why does hydrogen sulfide have to be tested on site?

University of Georgia Extension explains that hydrogen sulfide escapes from water very quickly, which makes it very difficult to test in a laboratory after shipment. The gas that gives the rotten-egg odor is gone from the bottle before the lab opens it. A field test at the tap, or a lab that samples on site, is the reliable method for that one line of the panel.