Testing
Test the right things, once
A treatment plan is only as good as the numbers behind it, and a cheap strip kit will not produce numbers worth planning from. Six parameters settle most decisions.
The core panel
Every one of these changes a decision. Skipping any of them means guessing at something.
| Parameter | Why it changes the plan | Threshold |
|---|---|---|
| Iron | Decides whether a filter is needed and, with the form, which kind. | 0.3 ppm |
| Manganese | Sets the pH target when present, which changes the whole train. | 0.05 ppm |
| Hardness | Decides whether a softener is worth it and how large it must be. | 7 gpg |
| pH | Decides whether an oxidising filter will work at all, and whether your plumbing is dissolving. | 6.5 to 8.5 |
| Total coliform and E. coli | The only result on this list that can change what you do today. | Absent |
| Nitrate | A health standard, and a signal that surface water is reaching the aquifer. | 10 ppm as N |
Worth adding, depending
| Hydrogen sulfide | Worth measuring rather than guessing from the smell, because the treatment changes with level. | No federal standard |
|---|---|---|
| Total dissolved solids | Explains a mineral or salty taste and affects membrane sizing. | 500 ppm |
| Tannins | Explains yellow or tea-coloured water, and they interfere with iron filters. | No federal standard |
| Arsenic | No taste, no smell, no visible sign, and regional, so the area's history matters. | 0.01 ppm |
| Copper and lead | Specifically where pH is low or there is blue-green staining, because acidic water mobilises both. | See EPA action levels |
Where to have it done
Start with your county or state health department. Many run a laboratory or publish a list of certified ones, some subsidise testing for private wells, and they know what is common in your area, which a national mail-in kit does not. For anything involving bacteria, nitrate or arsenic, a certified laboratory is the only result worth acting on.
Strip kits from a hardware store have a use: they are fine for watching hardness change after a softener goes in, or for confirming that iron is roughly where you thought. They are not adequate for deciding what to buy, and they are not adequate for anything health-related.
On test strips, and on free tests
The Private Well Class, run by the University of Illinois and RCAP with EPA funding, does not recommend test strips, which it callsprone to have false positives and false negatives which could lead you to think your water is safe to drink when it is not. It makes one exception, for pH strips.
Precision is the smaller problem. There is no meaningful strip test for coliform or E. coli, and the health-based decisions on this page turn on thresholds where a strip's resolution is worst: nitrate at 10 ppm, arsenic at 10 parts per billion. Reading a strip is also a colour-matching task, so the largest source of error is often who is holding it.
A free test offered by a company that sells treatment equipment is usually a hardness titration. It is not wrong, and it does not cover iron, manganese or anything health-related, which are the numbers that decide what you need. Penn State Extension recommends a third-party test before buying a softener specifically because an independent resultwill protect you from being oversold.
Penn State also warns about a specific sales tactic: vendors usingcolorful home water tests or other methods to scare or pressure homeowners into buying water treatment equipment on the spot. Their advice is to never decide quickly and to confirm any in-home result through an independent lab. Worth knowing before anyone arrives with a demonstration kit.
Taking a sample that means something
- Use the containers the lab supplies and follow their instructions exactly. Bacteria sampling in particular uses a sterilised bottle with a preservative, and rinsing it ruins the test.
- Sample from an untreated tap where possible, ahead of any existing equipment. An outside tap close to the well is usually best, and a sample taken after a softener describes the softener rather than the well.
- Remove aerators and hose attachments first, and let the water run several minutes so you are sampling the well rather than what has been standing in the pipe.
- Get it to the lab quickly, refrigerated if there is any delay. Bacteria results have a short hold time and a sample that sits overnight in a warm car is not a result.
- Note whether the water was clear or already coloured when drawn. That observation distinguishes dissolved iron from iron that has already oxidised, and it changes the equipment.
How often
The CDC recommends testing at least once a year for total coliform bacteria, nitrate, total dissolved solids and pH, and checking the well itself each spring for mechanical problems. The wider panel runs on a longer cycle, and authorities disagree about how long: Penn State and NC State say three years, while others separate metals from pesticides and put them on two-year and five-year cycles.
Retest immediately, rather than waiting for the cycle, when there is flooding or land disturbance nearby, after any repair to the well or plumbing, when the taste, colour or smell changes, when you are told there is a problem with water in the area, and, in the CDC's own list of triggers, when someone in the household becomes pregnant or a child starts living there.
Penn State Extension reports that studies have found around half of private water systems fail at least one drinking water standard, and that many pollutants have no symptoms at all and show up only in a laboratory result.
Private wells sit outside the Safe Drinking Water Act, so nobody does this on your behalf and nobody will tell you when something changes.
What each result means
Coliform and E. coli in well water
The one result that is about the well's physical condition rather than the water's chemistry. Bacteria in a well mean something is getting in, and disinfection treats the consequence rather than the cause.
Nitrate in well water
A genuine health standard rather than a staining threshold, and the population at risk is infants under six months. It is also a signal about the well itself, because nitrate is not naturally abundant in deep groundwater.
Iron in well water
The most common well water complaint in the country. Above 0.3 ppm it stains everything water touches, and the form it arrives in decides whether a filter or a softener is the right answer.
Manganese in well water
Iron's quieter companion. It stains black or grey rather than orange, shows up at a twentieth of iron's concentration, and needs a distinctly higher pH to remove.
Hard water from a well
Dissolved calcium and magnesium. It scales water heaters, coats fixtures, stops soap working, and shortens the life of every appliance that heats water.
Low pH (acidic) well water
The measurement that quietly decides more than any other number on the report. Low pH dissolves plumbing, and it slows the oxidation that every iron filter depends on.
Hydrogen sulfide in well water
The rotten egg smell, and the one water problem people notice instantly. Your nose finds it at concentrations a lab would call trace, and the treatment depends entirely on how much there is.