What should you test your well water for?

What a water test can and cannot tell you

A water test does not tell you whether your water is good. It tells you whether specific named things are present, and at what concentration. Everything else about the result is interpretation. The first piece of interpretation is which standard a number gets compared against.

The EPA maintains two sets. National Primary Drinking Water Standards are health based and enforceable for public systems. Each one carries a maximum contaminant level, or MCL. National Secondary Drinking Water Standards are different in kind.

The University of Arizona's well owner guidance puts it plainly: the secondary standards are non-mandatory, they cover fifteen contaminants, and the EPA does not enforce them Source 4: University of Arizona Superfund Research Program, Well Owner's Guide4.

The Texas Well Owner Network is blunter about what they are for. Secondary standards, it writes, are set only for aesthetic considerations, such as taste, color and odor, and water is likely to taste bad before it becomes unhealthy to drink Source 2: Texas Well Owner Network, Well Owner's Guide to Water Supply2.

Neither set applies to you by law. A private well is not a public water system, and no federal standard obliges a homeowner to test anything.

The standards are still the right yardstick. They are what a laboratory will compare your result against, and what a treatment decision will be argued from. But the distinction between the two sets is the whole of this page, and it is the thing most testing advice leaves out.

Hold on to one number while you read the rest. Nitrate's MCL is 10 milligrams per liter measured as nitrate nitrogen, and the Texas guidance names the reason it is set there: infants under six months drinking water above it can develop methemoglobinemia, in which the blood cannot carry enough oxygen to the body's cells Source 2: Texas Well Owner Network, Well Owner's Guide to Water Supply2. That is a health limit with a mechanism behind it. There is no equivalent sentence anywhere in the secondary standards, because there is no equivalent harm.

The three annual panels, and why they differ

Three institutions publish an annual well water test. All three are credible. All three are current. All three recommend something different.

NGWA recommends two named tests plus local judgment. Its 2021 well owner guide says owners should test their water at least annually for bacteria, nitrates, and any contaminants of local concern. It directs the reader to a local health or environmental health department to find out what local concern means where they live.

The guide then does something unusual, worth quoting because it is the only acknowledgement of its kind in the corpus behind this page. NGWA recommends testing annually for bacteria and nitrate, it says, though organizations may differ on their recommendations Source 1: National Ground Water Association, Well Owner's Guide 20211.

The Texas Well Owner Network recommends the same two, and argues against a third. Its frequency table is explicit: annually, test for total coliform bacteria and nitrate. It lists total dissolved solids as something you may choose to monitor for trends, not as part of the test.

It gives its reasoning in a footnote most readers never reach. Annual testing may not be needed for these chemicals, it says, because they usually occur naturally and their concentrations do not change over time Source 2: Texas Well Owner Network, Well Owner's Guide to Water Supply2.

Oklahoma State Extension recommends four. At minimum, its well water guidance says, water should be tested every year for nitrates, total dissolved solids, pH, and fecal coliform Source 3: Oklahoma State University Extension, Well Water Basics BAE-15443. Same two health parameters, plus the two that Texas explicitly set aside.

So the disagreement is entirely about pH and total dissolved solids. By the previous section, that is not really a disagreement about testing at all. Those two are secondary standards.

They are not health limits. They do not carry an MCL that means anything about safety. Both of the sources that leave them out say why: they describe conditions that are stable in an aquifer and that announce themselves through taste, staining and scale long before they mean anything.

That does not make them worthless. It makes them a different test with a different job. pH and total dissolved solids tell you about corrosion, scale, and whether a treatment system will work or foul.

They are the numbers a plumber or a treatment installer wants. They are baseline numbers, most useful once and then occasionally. That is exactly how Texas frames them.

Read that way, the three lists collapse into one coherent answer. Test bacteria and nitrate every year, because those answer whether the water can hurt someone. Establish pH and total dissolved solids once, as a baseline.

Repeat them when something changes, or when you are about to spend money on treatment. Add whatever your county says is a local problem, because that is the part no national guidance can supply.

This matters in dollars, not just in theory. A four parameter annual panel is priced as one thing and sold as one decision. A homeowner running it every year is paying for a health test and an operational test together, annually. Two of the three authorities here say the operational half does not need repeating on that schedule.

What to test for beyond the annual panel

The annual panel is a floor, not a plan. Four situations change it.

• A new, repaired or reconditioned well. Michigan's water well construction manual requires testing initially, before the well goes into service, to demonstrate the water is free of coliform bacteria Source 5: Michigan EGLE, Water Well Construction Manual5. Disinfection during construction is routine. The test shows it worked. If you have had a well repaired, pulled, or had the casing or pump worked on, you are in the same position as a new well.
• Anything of local concern. This is NGWA's phrase and it is doing real work. Arsenic, fluoride, radon and uranium are regional. So is anything industrial or agricultural near you. Your county or state health department knows which apply to your area. No national list can tell you.
• A change you can detect. A change in color, odor or taste is the Texas guidance's monthly homeowner check, and it is a trigger for a test rather than something to wait out Source 2: Texas Well Owner Network, Well Owner's Guide to Water Supply2.
• Illness in the household. NGWA names this directly: test the drinking water annually for bacteria, or when family or guests are experiencing recurring incidences of gastrointestinal illness Source 1: National Ground Water Association, Well Owner's Guide 20211. Recurring stomach upset in a household on a private well is a water test, not a coincidence.

Two more triggers are worth stating, because they are common and rarely on anyone's list. Flooding over the wellhead contaminates a well regardless of its construction. A real estate transaction usually has its own required panel, set by the lender or the state rather than by any of the guidance here.

How often, and what actually triggers a retest

Once a year, for bacteria and nitrate. That is the answer, and all three institutions agree on it.

The more useful question is what resets the clock. An annual test taken on the same date every year, without reference to what has happened in between, is a calendar habit rather than a monitoring plan.

A retest is triggered by any of the following, regardless of when the last one was:

• Work on the well, the pump or the casing
• Flooding at or near the wellhead
• A change in taste, smell, color or clarity
• Recurring gastrointestinal illness in the household
• A neighboring well testing positive for something
• A new activity nearby, whether that is drilling, a feedlot, or a fuel tank

A positive coliform result also has its own follow-up. That is not the same as an annual retest. Michigan's guidance is useful on the distinction: a routine coliform test detects both fecal and nonfecal coliform, and a positive result on the fecal indicator suggests recent fecal contamination and a greater risk that pathogens are present Source 5: Michigan EGLE, Water Well Construction Manual5.

Those two results mean different things, and lead to different next steps. That is the subject of reading your results, rather than of ordering the test.

How to actually get it tested

Start with your county or state health department, because for the health panel it is often free or low cost. This is not a technicality and it is not a fallback. Three of the sources behind this page route the homeowner there first.

NGWA sends owners to a local health or environmental health department both to find out what is of local concern and to find laboratories Source 1: National Ground Water Association, Well Owner's Guide 20211. Michigan's manual notes that sample bottles can be obtained from some local health department offices Source 5: Michigan EGLE, Water Well Construction Manual5. Oklahoma points at its state environmental quality department for the testing process and how to interpret results Source 3: Oklahoma State University Extension, Well Water Basics BAE-15443.

What is available varies by county, and falls into four outcomes:

• Some health departments run the bacteria test at no charge
• Some charge a small fee
• Some subsidize it seasonally
• Some only provide the bottles and a list of certified laboratories

That variation is exactly why the health department is the first call rather than the last. All four outcomes are worth the phone call. All four are cheaper than starting anywhere else, and the same call tells you what local contaminants your area actually has.

Then a certified laboratory, and the certification is the point. A laboratory certified by your state for drinking water analysis produces a result. A lender, a health department or a treatment installer will accept it. An uncertified result is a number without standing.

Sample handling is where a good test goes wrong. Michigan's requirement is specific and it is the tightest constraint on the whole exercise: samples must be received within twenty four hours of collection, or be held below six degrees Celsius, which is about forty three Fahrenheit Source 5: Michigan EGLE, Water Well Construction Manual5. That single rule decides most of the practical logistics.

It rules out mailing a bacteria sample on a Friday. It means collecting in the morning rather than the evening. It is why the laboratory supplies the bottle and the instructions, rather than leaving you to improvise either.

Home test strips are a different instrument with a different job. They are quick, cheap and useful for tracking something you already know about, such as hardness before and after a softener. They are not a substitute for a certified laboratory result on the health panel. No result from one should be used to decide that water with a bacteria or nitrate question is safe.

Requirements vary by county. Your county health department has the final word on permits, inspections, and what is allowed on your property.

What determines the price

This guide does not quote a price for a water test. The reason is worth one sentence: test pricing varies by state, by laboratory and by county subsidy. A number published here would be wrong somewhere the day it went up. What is stable is what drives it.

Panel size drives it most. A two parameter health panel and a twenty parameter scan are different products. This is the practical reason the panel split above is worth understanding before you order anything. It is the difference between buying one test and buying two.

Certification drives it next. A state certified drinking water laboratory costs more than an uncertified analysis or a strip kit. It is the only one of the three that produces a result with standing.

County subsidy moves it furthest. For the bacteria test specifically, the spread between a subsidized county program and a private laboratory is the largest single variable on this page. That is why the section above starts where it does.

Local contaminants add to it. Arsenic, radon, uranium and volatile organics are individually priced add ons. Whether you need any of them is a local question.

To get a real number, ask your county health department for its current fee schedule. Ask a certified laboratory for its current price list for the panel you actually need. Both are a phone call, both are current, and neither is a national average.