Taking a well water sample correctly comes down to choosing the right faucet, flushing your pipes thoroughly, and keeping the sample clean during collection and transport. A bad sample gives you bad results, so the technique matters as much as the test itself. The EPA recommends testing your private well at least once a year for bacteria, nitrates, total dissolved solids, and pH.
Where to Collect the Sample
The best sampling point is the tap or spigot closest to your well, ideally at or near the well head or pump house, before the water passes through any storage tanks, pressure tanks, or treatment systems like water softeners or filters. This gives you the most accurate picture of what’s actually in your groundwater. An outdoor spigot near the wellhead is often the most practical choice.
If you can’t access a tap near the well, you can sample from a kitchen faucet, but you’ll need to flush much more water to clear out everything sitting in your pressure tank and interior plumbing. Open several taps in the house during the flush to force a complete exchange of fresh water through the tank and pipes. Before you collect from any indoor faucet, remove aerators, screens, hose attachments, and any filter devices. These can harbor bacteria and skew your results.
Note the plumbing material in your home (PVC, copper, galvanized iron) if you can identify it. This is useful context for your lab, especially if you’re testing for metals.
Flushing the Lines
Before collecting any sample, you need to purge stagnant water from the pipes so you’re capturing fresh groundwater. Open the cold water tap fully and let it run for at least 5 to 6 minutes. A good rule of thumb: the water temperature will stabilize once the stagnant water has cleared and fresh well water is flowing. That temperature change is your signal that flushing is complete.
If you’re sampling past a pressure tank, flushing takes longer because you need to cycle the entire volume of the tank. Opening multiple faucets in the house speeds this up. Once the lines are flushed, reduce the flow to a steady, gentle stream. You don’t want water splashing off the sink basin or surrounding surfaces back toward the faucet or sample bottle.
The One Exception: Testing for Lead
Lead testing flips the flushing rule. If you’re checking for lead or copper, you want a “first draw” sample, meaning water that has been sitting in your pipes for at least 8 hours, typically overnight. This stagnant water absorbs the most lead from pipes, solder joints, and fixtures, so it represents the worst-case scenario for what you might actually drink first thing in the morning.
To do this, don’t run any water in the house for at least 8 hours (overnight is easiest). Then collect 250 mL from the tap without flushing first. If that sample comes back high, a follow-up “flush sample” collected after running the water for 30 seconds can help pinpoint whether the lead is coming from the fixture itself or from plumbing behind the wall.
Collecting a Bacteria Sample
Bacteria testing requires the strictest technique because you’re trying to detect contamination in your well, not contamination you introduced during collection. Your lab will provide a sterile bottle, typically a 125 or 150 mL plastic container. Do not rinse it. Do not touch the inside of the bottle or the inside of the cap.
After flushing the lines, reduce the water flow to a gentle stream. Open the sterile bottle and hold the cap by its outside edges only. Do not set the cap down on any surface. Fill the bottle to just above the 100 mL line, leaving about an inch of headspace at the top. Cap it immediately.
Some labs recommend disinfecting the faucet mouth with a flame or alcohol wipe before collecting a bacteria sample. Ask your lab whether they want you to do this, as protocols vary. The key principle is the same either way: nothing except well water should touch the inside of that bottle.
Getting Your Sample to the Lab
Once you cap the bottle, place it in a cooler with ice right away. Samples need to stay cold, around 4°C (roughly 39°F), from the moment you collect them until they reach the lab. For bacteria samples especially, time matters. Get your sample to the lab the same day if possible, or ship it overnight. The longer a bacteria sample sits, the less reliable the results become.
Nitrate samples are more forgiving on time (labs can hold them up to 28 days with proper chemical preservation), but unless you’re adding preservatives yourself, which most homeowners aren’t, treat every sample as time-sensitive and get it delivered quickly.
Getting a Test Kit
You don’t need to source your own bottles or preservatives. Most state-certified labs and mail-order testing services ship you everything you need: sterile containers, labels, instructions, and a prepaid return mailer. Your state health department or environmental agency can point you to certified labs in your area. Some states run their own testing programs at subsidized rates.
Contact the lab before you collect. They’ll tell you exactly which containers to use for each test, whether any bottles contain chemical preservatives (don’t dump those out), and how to label and ship your samples. Following their specific instructions is the simplest way to avoid a rejected sample.
What to Test and What It Costs
At minimum, test annually for total coliform bacteria (including E. coli), nitrates, total dissolved solids, and pH. These cover the most common and most dangerous well water contaminants. You should test immediately, outside your annual schedule, if you notice any change in your water’s taste, color, or smell, if there’s been flooding or construction near your well, or if you’ve repaired or replaced any part of your well system. Households with infants, elderly adults, or pregnant or nursing women may want to test more frequently.
Costs vary by lab, but state-run labs tend to be the most affordable. As a reference point, Michigan’s state lab charges $23 for a coliform and E. coli test, $41 for nitrate and nitrite, and $66 for a partial chemistry panel covering ten common parameters like hardness, iron, sodium, and fluoride. A complete metals screen covering lead, arsenic, mercury, and twelve other metals runs about $136. Specialized tests cost more: volatile organic compounds run around $147, and PFAS testing (the “forever chemicals” that have drawn increasing attention) costs roughly $320. Private and mail-order labs may charge more, but they often bundle multiple tests into a single kit for convenience.
If you’ve never tested your well, or if you’ve just moved into a home with a well, a comprehensive panel covering bacteria, nitrates, pH, hardness, metals, and any contaminants common in your region is worth the upfront cost. After that baseline, annual bacteria and nitrate testing is usually sufficient unless your situation changes.