How often should you test well water?

Short answer

Test the well water once a year, and have the well inspected at the same time. The yearly test is for bacteria and nitrates, the contaminants most likely to show up in a private well, and it's done by a certified lab from a sample you collect. Test right away, outside the schedule, after flooding, nearby construction, or any change in the water's taste, smell or color. The sampling takes 30 to 60 minutes, a mail-in lab kit costs $20 to $150, and a professional test with an inspection runs $100 to $500.

Why it matters

A private well has no utility behind it. Nobody tests the water but you, and the contaminants that matter most are invisible. Bacteria from a septic system or animal waste don't change the taste. Nitrates from fertilizer or septic effluent don't either, and they're a particular danger to infants. A well can go from fine to unsafe after one wet season, one new neighbor, or one crack in its cap, and the only way to know is to test.

The inspection covers the hardware. The well cap, the casing, the pressure tank and the pump all wear, and a cracked cap or a casing that's settled lets surface water and insects straight into the well. A pump that's starting to fail runs longer and hotter before it quits, and quitting usually happens on a holiday weekend. A yearly look finds the loose cap and the tired pump while they're small problems.

When to do it more often

The schedule is yearly, with these reasons to test immediately:

Flooding, especially if water reached the well head. Floodwater carries everything it passed through.
Construction nearby, including a new septic system, a new well, or drilling of any kind.
A change in taste, smell or color. Cloudy, salty, metallic or sulfurous water all mean something changed in the well or the water table.
Someone in the house gets sick with no other explanation, or a baby or a pregnant person joins the household, which raises the stakes on nitrates.
Repairs to the well or the pump. Test afterward to be sure nothing got in.

What you need

A sterile sample bottle from the lab, with its instructions, which usually say to collect from a cold tap after running it and removing the aerator

Steps at a glance

Order a test kit from a certified lab, or book a well service company to sample and inspect.
Collect the sample exactly as the lab's instructions say, from a clean tap with the aerator off, into the sterile bottle without touching the inside.
Get the sample to the lab within its time limit, usually the same day, cooled as directed.
While waiting for results, walk the well head: look for a cracked or loose cap, a casing that's settled or leaning, and standing water or debris around it.
Listen to the pump cycle and note how long it runs, and check the pressure tank and switch for rust or leaks.
Read the results against the lab's limits, and keep them with last year's to spot a trend.

You're done when the results are back and within limits, and the well head is capped, sealed and dry.

Signs it's overdue

A change in taste, smell or color in the water.
Sputtering faucets, which means air in the line and often a pump drawing on a low well.
Lower pressure than usual.
Sediment in the water, or in the filter if you have one.
A well cap that's cracked, loose or missing its screen.

DIY or pro

Testing is pro-recommended, and the lab is the pro. You can collect the sample yourself with a mail-in kit for $20 to $150, and the result is as good as the sample. Follow the bottle's instructions exactly, because a sample contaminated at the tap tells you nothing about the well.

A well service company charges $100 to $500 to take the sample, run the lab work, and inspect the well head, pump and pressure tank. That's the better choice for the first test after buying a house, for any well with symptoms, and for anyone who'd rather have someone who knows pumps listen to theirs. The hardware inspection is the part a kit can't do.

FAQ

What should well water be tested for?

Bacteria and nitrates every year. Depending on where you live, the local health department may suggest adding arsenic, lead, radon or other contaminants on a longer cycle.

How much does a well water test cost?

A mail-in lab kit is $20 to $150, depending on how many things it tests for. A professional test with an inspection is $100 to $500.

What if the well water test comes back with bacteria?

Have the well shock chlorinated by a well company, then test again. If bacteria keep coming back, the well needs a permanent fix, such as a new cap or a treatment system.

How often should a well pump be inspected?

Once a year, along with the water test. Listening to how long it runs and checking the pressure tank catches most problems early.