Water Safety Guide
Well Water Testing: What a Home Kit Catches and What Needs a Lab
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This page is about what is in the water. For how it gets out of the ground and where it is kept, see the well pump guide and water storage.
If your water comes from a private well, nobody tests it but you. There is no utility, no monthly report, and no agency that will call you when something changes.
This guide covers what to test for, how often, and the part most buying guides skip: the difference between a strip that screens your water and a laboratory that can actually clear it.
Last updated: August 28, 2026 · Sourced from the US EPA, the EPA National Primary Drinking Water Regulations, and Penn State Extension
The Short Answer
Test your well once a year through a certified laboratory for total coliform bacteria, nitrate, total dissolved solids, and pH. Add tests for whatever is common in your local geology and land use.
Home strips are useful for watching your water between those annual tests. They are not a substitute for one. A strip can tell you something looks wrong. It cannot tell you your water is safe.
Nobody Is Testing Your Well For You
Public water systems are regulated. They are monitored, tested, and reported on, and the utility has to tell you when something goes wrong. Private wells sit entirely outside that. The EPA puts the responsibility plainly: “you alone are responsible for assuring that it is safe”. (EPA 816-F-05-013)
There is a second reason to test on a schedule even when nothing seems wrong. A yearly result builds a record. The EPA notes that this record helps in solving future problems, and in obtaining compensation if someone damages your water supply. If a neighbouring operation contaminates your aquifer, the difference between a complaint and a claim is often whether you can show what your water looked like before.
Well water also changes. Rainfall, a wet spring, a new septic field, a dry year that drops the water table, road salt, a neighbour drilling: all of them can move your numbers without changing anything you can see at the tap.
What to Test Every Year
The EPA is specific about the annual baseline: “Test your private well annually for total coliform bacteria, nitrates, total dissolved solids, and pH levels”. (EPA) Penn State Extension splits it slightly differently, calling for coliform and E. coli every year, with pH and total dissolved solids “every three years”. (Penn State Extension)
Those four tests are not four versions of the same thing. They answer four different questions.
| Test | What it answers | Where the problem comes from |
|---|---|---|
| Total coliform bacteria | Is there a path from the surface into your well | Cracked casing, bad seal, shallow well, flooding, septic |
| Nitrate | Is fertiliser, manure, or septic waste reaching the water | Farm ground, feedlots, lawns, a failing septic field |
| Total dissolved solids | How much mineral is in the water overall | Geology, road salt, seawater intrusion near coasts |
| pH | Is the water eating your plumbing | Naturally acidic groundwater, which then leaches metal |
pH is the one people skip, and it is worth keeping. Acidic water does not hurt you directly. It dissolves the pipe it travels through, which is how copper and lead get into water that arrived at the house clean.
Nitrate and Infants: Test This On Its Own Schedule
Nitrate is the one contaminant on this page with a specific, urgent risk group. The EPA limit is 10 mg/L, measured as nitrogen, and the stated health effect is blunt: “Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die”. (EPA)
Because of that, nitrate has its own timing advice. The EPA recommends testing for nitrate in the early months of a pregnancy, before bringing an infant home, and again during the first six months of the baby’s life. It also names the best window: “It is best to test for nitrate during the spring or summer following a rainy period”, because that is when it peaks.
Boiling makes nitrate worse, not better. Boiling removes water as steam and leaves the nitrate behind, so it raises the concentration. Never boil well water to make it safe for an infant.
What Else to Test For, and When
Beyond the annual four, testing is driven by what is near you and what your water is doing. The EPA publishes a plain mapping of condition to test. It also gives a useful piece of budget advice: “Tests can be expensive; limit them to possible problems specific to your situation”. Do not order a hundred-analyte panel because it feels thorough. Order the tests your surroundings justify.
| If this is true near you | EPA recommends testing for |
|---|---|
| Intensive agriculture | Nitrate, pesticides, coliform bacteria |
| Recurring stomach illness in the house | Coliform bacteria |
| Household plumbing contains lead | pH, lead, copper |
| Radon-rich region, or radon in indoor air | Radon |
| Gas drilling operation nearby | Chloride, sodium, barium, strontium |
| Coal or other mining nearby | Metals, pH, corrosion |
| Fuel smell, gas station, or buried fuel tanks | Volatile organic compounds |
| Dump, landfill, factory, or dry cleaner nearby | VOCs, total dissolved solids, pH, sulphate, chloride, metals |
| Salty taste, coastal area, or heavily salted road | Chloride, total dissolved solids, sodium |
| Stained fixtures and laundry | Iron, copper, manganese |
| Scaly residue, soap will not lather | Hardness |
Source: EPA, Home Water Testing (816-F-05-013). For taste, odour, and staining problems the EPA suggests testing sulphate, chloride, iron, manganese, hardness, and corrosion “every three years” rather than annually.
Geology You Cannot Taste: Arsenic, Uranium, Radon
Three contaminants deserve their own mention because they are invisible, they are local, and they have nothing to do with how well you maintain your well. They come out of the rock.
- Arsenic. EPA limit 0.010 mg/L. The stated effects are skin damage, circulatory problems, and increased cancer risk. Common in parts of New England, the upper Midwest, and the Southwest.
- Uranium. EPA limit 30 micrograms per litre, with increased cancer risk and kidney toxicity named as the effects.
- Radon. A gas that enters water from surrounding rock. If your region is radon-rich or your indoor air already tests high, the EPA lists water radon as a test worth running.
None of these appear on a general test strip. None of them change the taste of the water. The only way to find them is to ask for them specifically, which is why the local question, what is common in my area, matters more here than any product choice.
Home Kit or Certified Lab: What Each One Actually Establishes
This is the part worth being precise about, because the marketing around home kits blurs it. A strip and a lab are not cheap and expensive versions of one thing. They answer different questions with different levels of confidence.
| Home strips | Mail-in lab kit | County or state lab | |
|---|---|---|---|
| What it is good for | Watching between real tests | A broad annual picture | Bacteria, nitrate, local problems |
| Reads results how | You match a colour by eye | Instrument analysis | Instrument analysis |
| Sterile sampling | Usually not | Yes, containers supplied | Yes, containers supplied |
| Accepted for a real dispute | No | Depends on the lab | Usually yes |
| Finds arsenic, uranium, radon | No | Only if the panel includes them | If you request them |
| Turnaround | Seconds | Days to weeks | Days |
The EPA leaves no ambiguity about which one counts: “Only use laboratories that are certified to do drinking water testing”. Penn State Extension adds the warning that matters when someone is standing in your kitchen offering a free test: “Be cautious of water test results from any uncertified lab or from water treatment salespeople”.
What a Home Test Does Not Establish
A strip can be genuinely useful. It is fast, it costs little, and checking hardness or pH monthly will show you a change worth investigating. But there are four things it cannot do, and knowing them is what keeps a strip honest.
- It cannot prove your water is bacteria free. The EPA requirement is explicit: “Samples for coliform bacteria testing must be collected using sterile containers and under sterile conditions”. A sample you scooped yourself into a rinsed bottle does not meet that standard. A contaminated sample can read positive when the well is fine, or be handled in a way that no longer represents the well at all.
- It cannot see the contaminants with the worst outcomes. Arsenic, uranium, radon, pesticides, and volatile organic compounds are not on a general strip panel. These are exactly the ones with no taste and no colour.
- Its precision depends on your eyes. A colour-match reading is a judgement made by a person, in whatever light they happen to be standing in. Two people can read the same strip differently, and someone with colour vision deficiency may not be able to read it at all.
- It carries no weight in a dispute. If a neighbouring operation contaminates your water, a photo of a test strip is not evidence. A dated certified laboratory report is.
Use a strip the way you use a smoke alarm going off: as a reason to look closer, never as a certificate that everything is fine. A clean strip and an untested well are the same amount of evidence about safety.
When to Test Immediately, Whatever the Calendar Says
The annual schedule is a floor. The EPA lists conditions that should send you for a test straight away:
- You notice a change in taste, colour, or odour.
- There are known groundwater or drinking water problems in your area.
- Conditions near the well changed, including flooding, land disturbance, new construction, or industrial activity.
- You replaced or repaired any part of the well system, including pipes, pumps, or the casing.
- Someone in the house is pregnant or nursing, or there is an infant, or there is unexplained illness.
Flooding is the one homesteaders underestimate most. Water over a wellhead is a direct path from the surface into the well, and the well can look completely normal afterwards.
How to Get a Real Test Done
- Call your county health department first. Many test for bacteria and nitrate directly, often cheaply, and they know the local contaminants better than any national panel does.
- Ask your state drinking water programme for the certified lab list. The EPA also runs a Safe Drinking Water Hotline on 800-426-4791.
- Use the lab’s own containers. Do not supply your own bottle. Follow the collection instructions exactly, including how long to run the tap first.
- Get the sample back fast. Bacteria samples are time sensitive and usually need to be kept cold. A sample that sits over a weekend is a wasted test.
- Keep every report. This is the record that turns into leverage later.
Testing Tools, and What Each One Is For
Read the note on each of these. Only the first is a laboratory result. The other two are screening tools for watching your water between real tests, and neither one can clear a well.
Mail-in water test analysed by certified labs
This is the tier that produces an actual laboratory result, covering heavy metals, coliform and E. coli, and the contaminants a strip cannot see. It ships sterile containers and collection instructions.
Check your county health department first. Many test bacteria and nitrate directly, cheaper, and they know your local contaminants better than a national panel does.
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Bacteria-only screening test
A single-purpose bacteria screen for checking after well work, flooding, or a taste change, without waiting on a full annual panel.
A screening result, not a certified one. A positive means stop drinking it and call a lab. A negative does not clear the well, and it is not evidence in a dispute.
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Multi-parameter test strips
For watching hardness, pH, iron and chlorine month to month, so you notice a change between annual tests rather than after it has been true for a year.
Screening only. Strips are read by matching a colour by eye, they cannot detect arsenic, uranium, radon or VOCs, and a clean strip is not evidence your water is safe to drink.
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Common Mistakes
- Treating a clean strip as an all clear. It rules out almost nothing that matters for health.
- Buying treatment before testing. A softener does not remove nitrate. A sediment filter does not remove arsenic. Match the system to a measured problem.
- Boiling to fix nitrate. Boiling concentrates it. This one is actively dangerous for infants.
- Testing only when something tastes wrong. The contaminants with the worst outcomes have no taste at all.
- Accepting a free test from whoever is selling the system. Penn State Extension names this one directly.
- Skipping the test after well work. Opening the system is exactly when contamination gets in.
Common questions
How often should I test my private well?
The EPA says to test every year for total coliform bacteria, nitrates, total dissolved solids, and pH. Test right away, outside that schedule, if your water changes in taste, colour, or smell, if there has been flooding or new construction or digging nearby, or if you replaced or repaired any part of the well system.
Can a home test strip tell me if my well water is safe to drink?
No. A strip is a screening tool. It can flag a problem worth chasing, but it cannot clear your water. The EPA is direct about who should do the actual testing: only use laboratories that are certified to do drinking water testing. A clean strip result is not evidence your water is safe.
Why can a strip not prove my water is free of bacteria?
Because the sample itself has to be collected a certain way. The EPA states that samples for coliform bacteria testing must be collected using sterile containers and under sterile conditions. A cup from your kitchen and an open bottle do not meet that. If the sample is contaminated on the way in, the result is meaningless whichever way it reads.
What is the nitrate limit and why does it matter so much for babies?
The EPA limit is 10 mg/L, measured as nitrogen. The EPA states that infants below the age of six months who drink water containing nitrate in excess of the limit could become seriously ill and, if untreated, may die. That is why nitrate is one of the few tests with its own timing advice around pregnancy and a new baby.
Do I need to test for arsenic, uranium, or radon?
It depends on your geology, and that is a local question. These come from rock, not from anything you did. Ask your county health department or state environmental agency what is common in your area, then test for those specifically. The EPA limit for arsenic is 0.010 mg/L and for uranium is 30 micrograms per litre.
My water tastes fine. Do I still need to test?
Yes. The three contaminants that matter most for health, coliform bacteria, nitrate, and arsenic, have no taste, no smell, and no colour at the levels that matter. Taste tells you about hardness, iron, and sulphur. It tells you nothing about whether the water is safe.
How do I find a certified laboratory?
Start with your county health department, which often tests for bacteria and nitrate directly or will name a lab. Your state drinking water programme keeps a list of certified labs. The EPA also runs a Safe Drinking Water Hotline on 800-426-4791. Penn State Extension adds a warning worth repeating: be cautious of water test results from any uncertified lab or from water treatment salespeople.
Should I test before or after a water treatment system?
Both, and test before you buy anything. You cannot choose a treatment system sensibly until you know what is actually in the water, and a system sized for the wrong problem is money spent for nothing. Testing again afterwards is the only way to know the system is doing what it promised.