How Often to Test Well Water, and What to Test For

On this page 7 sections

1. 01The short answer: every year for bacteria, nitrate, pH and TDS
2. 02Why no one else will do it for you
3. 03When to test right away
4. 04Extra tests for where you live
5. 05Your first test after moving in: yearly, move-in, move-in plus local risks
6. 06How to take the sample so the result counts
7. 07What to do with the result

Test your well every year for four things: total coliform bacteria, nitrate, pH and total dissolved solids (TDS). The EPA and the CDC agree on that list. Test right away, outside the yearly routine, after a flood, after work on the well, or when the water changes in taste, smell or color. And once, ideally in your first months in the house, run a broader panel that adds arsenic, lead, iron, manganese and hardness, plus whatever your surroundings call for.

Send it to a state-certified lab, as the CDC advises. At the Penn State university lab, the yearly set costs $70 and the full move-in panel $220.

The short answer: every year for bacteria, nitrate, pH and TDS

The yearly test is bacteria, nitrate, pH and TDS. Arsenic every five years, or every year where it’s common. More often if someone in the house is pregnant or a baby is on the way.

Four sources are worth comparing, because they don’t say quite the same thing:

Penn State says pH and TDS every three years. We go with the EPA and CDC and say every year, because the extra cost is small: at Penn State’s lab, a bacteria-only test is $40; the $60 Standard package adds pH and TDS for $20 more, and $70 gets you nitrate too.

Wisconsin’s arsenic schedule is a sensible model even if you live elsewhere: every five years, and every year where arsenic is common or has shown up before. A USGS model estimated that about 2.1 million people drink from private wells with arsenic above 10 µg/L, with the highest odds along the West Coast, in Nevada, Arizona and New Mexico, and in parts of the Northeast, the Midwest and the Southeast. Your neighbor’s result is a clue, not your answer. More in arsenic in well water.

Why no one else will do it for you

Private wells fall outside the Safe Drinking Water Act, and most states don’t regulate them. If you don’t test, nobody does.

More than 43 million Americans, about 15 percent of the population, drink from a private well. The EPA is plain about it: the owner is responsible for the water. Most states offer programs to help, but few require anything. A 2020 review for Minnesota lawmakers counted, at the time, 13 states that required a coliform test when a new well is drilled, and three (Oregon, New Jersey, Rhode Island) that required a test when a house is sold. After that, there’s no schedule except yours.

It isn’t a formality. In a USGS study of 2,100 private wells, about one in five had at least one contaminant above a health benchmark. The American Academy of Pediatrics also recommends testing a private well every year.

The numbers you’ll compare against come from the EPA’s drinking water standards. Those are the legal limits for public water systems. No one enforces them on your private well, but they’re the yardstick labs and health departments use.

When to test right away

Don’t wait for the yearly date after a flood, work on the well, a change in the water, or trouble nearby.

The EPA’s list of reasons to test outside your routine:

• Flooding near the well.
• Digging or construction near the well (the EPA calls it land disturbance).
• Any repair or replacement of parts of the well system.
• A change in taste, smell or color.
• A known water problem in your area.

The EPA also lists recurring stomach trouble in the household as a reason to test for bacteria. Texas’s guide adds a loss of water pressure.

Two more moments the sources mention:

• After you shock chlorinate. The retest is how you know it worked. Georgia’s extension says to run the water for 5 to 7 days first; Montana State says at least 72 hours after the chlorine is flushed out. See how to shock chlorinate a well.
• After you install treatment. New Jersey’s health department advises a retest once a nitrate system is in. The same logic applies to any filter: a test is the only way to see that it does what the label claims.

If a test shows E. coli, stop drinking the water untreated and call your county health department or sanitarian. In the meantime, boil drinking water: Montana State says for at least one minute, Texas’s guide says two minutes at a full boil. Coliform or E. coli in your well walks through the next days.

Extra tests for where you live

The yearly four miss metals, radon, fuel and farm chemicals. Add tests based on what’s near your well and what you see in the house.

The EPA’s table links 16 situations to tests. We grouped them into the rows below and matched each to the package at the Penn State lab that covers it, so you can see what it costs. Prices are from Penn State’s published list (checked November 2026); every package includes the standard four tests (coliform, E. coli, pH, TDS).

A few notes on that table.

Two rows are ours, not the EPA’s: septic and arsenic. The septic row is the one most people miss. The EPA lists high nitrate or coliform in a well as one of the signs of a failing septic system. Your yearly test is also a check on your drain field. If nitrate creeps up year over year, read signs of a failing septic system and nitrate in well water.

For gas drilling, Penn State itself points you to an accredited lab that offers chain-of-custody testing if you want to document your water before or after drilling. Chain of custody means every hand the sample passes through is recorded, which is what you want if you ever have to show what your water was like before the drilling started.

Most of the health concern with radon in water comes from breathing it once it escapes into the air, according to an older EPA estimate. Georgia’s extension estimates about 1 pCi/L of extra radon in indoor air for every 10,000 pCi/L in the water. Test your indoor air too.

PFAS isn’t on any of Penn State’s drinking water packages. The EPA’s advice is to use a state-certified lab that runs an EPA method. A USGS sampling study found that at least 45 percent of U.S. tap water has one or more PFAS, at similar levels in private wells and public supplies. Whether to test depends on what’s near you; see PFAS in well water.

The CDC’s shortcut is simpler than any table: ask your local health department which of volatile organic compounds, lead, arsenic, mercury, radium and pesticides turn up in your area. They know the local geology and land use.

Your first test after moving in: yearly, move-in, move-in plus local risks

For the first test in a new house, go broad once: Penn State’s $220 Extensive panel covers far more than its $70 yearly set, and costs less than buying the pieces separately.

Why Extensive and not smaller packages: Trace ($130) has arsenic and lead but no nitrate. Add the Agriculture/Septic package for nitrate and you’re at $200, you’ve paid twice for the bacteria, pH and TDS tests, and you still don’t have iron, manganese, hardness, alkalinity, corrosivity, sodium, chloride or sulfate. Extensive has all of that for $20 more. Ordered one by one from Penn State’s list of individual analyses, the tests in Extensive come to at least $295 (bacteria $40, corrosivity $45, arsenic $30, lead $25, hardness $20, and $15 each for pH, TDS, nitrate, iron, manganese, copper, barium, chloride and sulfate; sodium and alkalinity aren’t sold separately). What Extensive drops from Trace are cadmium, chromium, nickel and zinc. If your health department mentions any of those for your area, add Trace.

Penn State is one lab in one state. Your state lab or a certified private lab will price differently. Use these numbers as a yardstick for what a fair panel includes. Where to get your well water tested covers finding a certified lab and comparing price lists.

If you’re still buying the house, do this test during the inspection period, not after closing. In Oregon the seller has to test for arsenic, nitrate and total coliform at an accredited lab; most states have no such rule. See buying a house with a well and septic.

How to take the sample so the result counts

Use the lab’s sterile bottle, don’t rinse it, sample from a clean tap that bypasses any treatment, and get bacteria samples to the lab within its time limit, which ranges from 6 to 48 hours.

A contaminated or mishandled sample gives a meaningless result. The Texas Commission on Environmental Quality lists “unsuitable for analysis” as a third outcome on a bacteria report, for example when someone rinsed out the bottle. These steps come from Texas’s 2023 guide and the University of Arizona’s extension sheet:

1. Get the kit from the lab. Bacteria samples need the lab’s sterile container. Some bottles have a little powder inside. That’s normal; don’t dump it out.
2. Pick the tap. Use a cold-water tap that doesn’t leak, never a hose, and never a tap that runs through a softener or filter if you want to know what’s in the well. (If you want to know whether your filter works, test after it, and say so on the form.)
3. Remove the aerator or screen from the faucet.
4. Disinfect the tap. Run it for a few minutes, turn it off, then either pass a butane flame over the opening for a few seconds (not on plastic parts) or spray it inside and out with a 10 percent bleach solution or 70 percent rubbing alcohol and let it sit several minutes.
5. Run the water again. Arizona says to let it run 2 to 5 minutes before you fill (Texas already ran it 3 minutes at full flow before disinfecting). Texas then turns it down to a slow, steady stream about the width of a pencil for filling.
6. Fill to the line or just above it without touching the inside of the bottle or cap and without splashing. Don’t rinse the bottle.
7. Label it with date, time and which tap, and put it on ice right away.

The two guides disagree on one thing: which tap. Texas prefers an outside faucet that points down and says not to use kitchen or bathroom sinks. Arizona prefers an indoor cold-water line and suggests the bathtub faucet. Follow the sheet that comes with your kit. Your lab knows how it wants samples taken.

For lead and copper, the lab may ask for two samples: one first-draw (the first water out of the tap after it sat unused, usually overnight) and one after running. Penn State’s lead package works that way. Follow the lab’s instructions for each bottle.

Time limits for bacteria samples

The limits differ by lab, so the one on your lab’s form is the one that counts. Arizona’s older sheet is the strictest and advises against mailing bacteria samples at all; Penn State and Texas build their kits around overnight shipping. If a certified lab is within driving distance, dropping the cooler off yourself takes the clock out of play.

Take bacteria samples early in the week. Penn State doesn’t accept them on Fridays, and many labs follow the same rule. If you ship, use overnight delivery. Results take about two to three days for a bacteria-only test in Texas’s guide and 10 to 14 business days for Penn State’s packages.

What to do with the result

Compare each number with the EPA level, check the units, and call your county for anything above the line on bacteria, nitrate, nitrite, arsenic, lead or PFAS.

A few yardsticks you’ll see on the report:

• Total coliform or E. coli: any positive result in a private well is a signal to act. The EPA’s coliform rule counts the share of positive samples per month at a public system, which doesn’t translate to one well.
• Nitrate: 10 mg/L measured as nitrogen. Check which form your lab reports; lab report units explains the difference.
• Arsenic: 10 µg/L, the same as 0.010 mg/L.
• Iron and manganese: 0.3 mg/L and 0.05 mg/L. These are secondary standards, about stains and taste, not health limits.

All of these are the legal limits for public water systems. They don’t apply to your private well by law, but labs and health departments use them as the yardstick. For bacteria, nitrate, nitrite, arsenic, lead and PFAS, call your county health department. They know the local geology and can explain what’s typical in your area. If someone in the house is pregnant or you have a baby on formula, ask your doctor as well.

How to read your well water test results goes through every line on a typical lab report. To go straight from your numbers to what fixes them, enter them in the Water Test Decoder. Then put next year’s test date in your calendar, and keep the report: a run of yearly results is how you notice a slow change.

Quick answers

How often should I test my well water?

Once a year for total coliform bacteria, nitrate, pH and total dissolved solids (TDS). That is what both the EPA and the CDC recommend. Test right away after flooding, work on the well, or a change in taste, smell or color.

What should a yearly well water test include?

Total coliform bacteria (with E. coli), nitrate, pH and TDS. At the Penn State lab that set costs $70 as the Agriculture/Septic package.

How much does a full well water test cost?

At the Penn State university lab, the Extensive package costs $220. It adds hardness, corrosivity, arsenic, barium, lead, copper, iron, manganese, sodium, chloride and sulfate to bacteria, nitrate, pH and TDS. Prices at other labs differ.

Who is responsible for testing a private well?

You are. Private wells are not covered by the Safe Drinking Water Act, and most states don't regulate them either, so no agency tests your well for you.

How fast does a bacteria sample have to reach the lab?

It depends on the lab, from as little as 6 hours to 48 hours. Penn State and the Texas Commission on Environmental Quality both use 30 hours. Many labs don't accept bacteria samples on a Friday.