Testing your well water in Idaho

The short version

Test for total coliform bacteria and nitrate every year. Runarsenic and lead once, because nothing about them is detectable by taste, smell or appearance. Use a laboratory certified for drinking water, not a hardware-store strip. And do it before anyone pregnant or any infant drinks the water, rather than after.

What to test for, and why each one is on the list

Total coliform and E. coli

The indicator that something is reaching your well that should not be — a cracked casing, a bad seal, surface water finding a path in. This is the one to run first and the one to repeat.

How often: Every year, and after any work on the well, flooding, or a change in taste or smell.

Nitrate

The contaminant Idaho has a mapped problem with. DEQ has designated 35 nitrate priority areas, and across them 682 of 4,393 sampled wells — 16% — came back above the EPA limit of 10 mg/L.

How often: Every year. Immediately, and before relying on the water, if anyone in the house is pregnant or there is an infant.

Arsenic

Occurs naturally in parts of Idaho groundwater and is invisible, tasteless and odourless. There is no way to know without a test.

How often: Once, early. Again if the well is deepened or a new one is drilled.

Lead

Usually not from the aquifer but from the plumbing between the well and the tap, which means the result depends on how the sample is taken.

How often: Once, and after any plumbing work. Ask the lab for a first-draw sample.

pH, hardness, iron and manganese

Not health limits so much as the things that wreck fixtures, stain laundry and decide which treatment equipment is appropriate.

How often: Once, and whenever you are quoting treatment.

What it costs

It depends on the lab and on how many analytes you ask for, and we are not going to print a range we have not gathered. Certified laboratories and public health districts publish their own fee schedules — ask two of them for a written price, the same way you would for drilling.

Where to get it done

Use a laboratory certified for drinking-water analysis. The Idaho Bureau of Laboratories maintains that certification, and your public health district can tell you which labs it accepts results from — which matters, because a district may require a test before it will issue a permit.

If your well is in a nitrate priority area

DEQ has designated 35 areas where sampling found nitrate worth tracking, and they are not equivalent: the share of sampled wells above the 10 mg/L limit runs from 4% in Twin Falls to 58% in Fort Hall, and the highest single reading recorded across them is 110 mg/L.

A designation describes an area, not your well. Two wells on the same road can differ by more than the map does, because depth and construction matter as much as location. It is a reason to test, not a result.

See all 35 nitrate priority areas, each with the number of wells DEQ sampled and what they found.

What a result does and does not settle

A test tells you what was in that sample, taken that way, on that day. It does not tell you what the well does in a wet spring or after a dry summer, and it does not certify the well. Keep the results, date them, and re-test rather than relying on a reading from several years ago — which is also the right answer when a seller hands you one.

Common questions

How do I get my well water tested in Idaho?

Through a laboratory certified for drinking-water analysis. The Idaho Bureau of Laboratories maintains the list of certified labs, and your public health district can tell you which ones it accepts results from and whether it requires a test for a permit.

What should I test my well water for?

At minimum total coliform bacteria and nitrate, every year. Arsenic and lead are worth running once because neither can be detected by taste, smell or appearance. If you are inside one of DEQ's 35 nitrate priority areas, nitrate is the one to do first.

How much does well water testing cost in Idaho?

It varies by lab and by how many analytes you ask for. Certified laboratories and health districts publish their own fee schedules, so ask two for a written price. We do not publish a range here because we have not gathered one we can point at, and a made-up figure is worse than no figure.

How often should a private well be tested?

Annually for bacteria and nitrate. Again after any work on the well, after flooding, if the taste, smell or colour changes, or before anyone pregnant or any infant starts drinking it.

Does anyone test private wells for me?

No. Public water systems are regulated and routinely monitored; a private well is the owner’s responsibility, and nobody tests it unless you arrange it. That is the single most important thing to know about owning one.

Can nitrate be treated?

Yes — reverse osmosis, ion exchange and distillation all address nitrate. Boiling does not; it concentrates it. Which approach fits depends on the reading and the household, which is a question for a treatment professional once you have a result in hand.

Source

Nitrate figures: Idaho Department of Environmental Quality, published through IDWR, retrieved 2026-10-19. Health district contacts are published by each district. Nothing on this page is a laboratory result for any specific well.