How to test well water

Testing splits cleanly into two categories, and conflating them is why people either overspend or miss something important.

The health panel tells you whether the water is safe. Coliform bacteria, nitrate, and — depending on your geology — arsenic. None of these can be tasted, smelled or seen, so observation tells you nothing at all. This is the testing that is not optional.

The nuisance panel tells you what equipment you need. Hardness, iron, manganese, pH, hydrogen sulfide, total dissolved solids. These you can often detect yourself, but you cannot quantify them by eye, and equipment is sized on numbers.

• Every year — coliform bacteria and nitrate. The two that matter most and change most.
• Every 3–5 years — a full chemical panel, or sooner if anything changes.
• Once, when you buy the property — arsenic, and anything your state flags locally, such as radon in water, uranium or fluoride.
• After any event — flooding, nearby construction, a new septic system, well or pump work, or any sudden change in taste, smell, colour or pressure.

Start with your county or state health department. Many run free or heavily subsidised testing for coliform and nitrate, sometimes seasonally, and they will tell you what is worth testing for in your specific area — which is genuinely local knowledge that no national guide can give you.

For a full panel, use a laboratory certified for drinking water analysis. State certification lists are public. A certified lab matters most for the health analytes, where the whole value is in detecting small amounts reliably.

Be a little cautious about free tests offered by companies selling treatment equipment. They are often a real measurement, but the person interpreting the result has an interest in the answer. If you use one, a paid test from an independent lab before making a large purchase is cheap insurance.

Sampling technique changes results more than most people expect, and a badly taken sample is worse than no sample because you will act on it.

Two kinds of sample answer different questions. A flushed sample — run the tap several minutes first — tells you about the water in the aquifer. A first-draw sample, taken from a tap unused overnight, tells you about your plumbing, and is the correct method when you are looking for copper or lead.

1. Use the container the lab provides. Bacteria bottles contain a preservative and must not be rinsed out.
2. For a bacteria sample, remove any aerator or hose, and disinfect the tap with a flame or bleach wipe before sampling.
3. Do not sample from a tap with a filter fitted unless you are specifically testing the filter's output.
4. Fill without touching the inside of the bottle or the cap, and fill to the marked line.
5. Refrigerate and get it to the lab within the stated hold time — usually 24 hours for bacteria. A sample that sits in a warm car is not a valid sample.

Strips and drop kits are genuinely useful for the nuisance panel. Hardness, pH, iron and total dissolved solids can all be measured well enough at home to size equipment with, and being able to retest freely after installing something is worth a lot.

They are not adequate for the health panel. Bacteria test kits give presence/absence at best and are easily confounded; nitrate and arsenic both need lower detection limits and better precision than a strip can deliver. Using a home kit to conclude that your water is safe is the one application to avoid.

A reasonable approach is a home kit for the numbers you will be adjusting and retesting, and a certified lab annually for the ones that decide whether anyone should be drinking the water.

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