My Well Water Failed a Test. Now What?
A lab report with one number over the line is not an emergency, but it is a decision. Here is how to read the report, what the common failures mean, and the order to deal with them.
Likely causes
- Coliform or E. coli bacteria
- Nitrate over 10 mg/L
- Arsenic or lead over the limit
- Secondary contaminants like iron or hardness flagged as exceedances
Tests to order
- Confirmation resample
- Full panel if only a basic test was run
- E. coli when total coliform is positive
Treatment options
- Shock chlorination and resample
- UV disinfection
- Reverse osmosis for nitrate and arsenic
- Certified treatment sized to the result
Read the report the way the lab does
Every line has a result, a unit and a limit. Primary contaminants have a health-based limit, called an MCL: bacteria, nitrate, arsenic, lead, uranium. Secondary contaminants have a nuisance limit: iron, manganese, hardness, pH, chloride. A failure on a primary is a stop-drinking-until-fixed situation for the people at risk. A failure on a secondary is a comfort and plumbing problem.
The order of operations
Bacteria first. A positive total coliform means the well is open to the surface somehow; positive E. coli means sewage or manure is reaching it. Use bottled water for drinking, shock the well, fix the wellhead, and resample after a week. Nitrate second, because it is dangerous to infants and pregnant women immediately and no boiling helps. Then arsenic, lead and uranium, which are long-term risks and are removed by point-of-use reverse osmosis or whole-house media. Secondary problems last.
One test is a snapshot
Wells change with the season and the weather. Before spending on treatment for a borderline result, take a second sample two to four weeks later. If both fail, treat. Keep every report; a buyer, a lender or a health department will ask for the history.
Should I stop drinking the water?
For bacteria, nitrate, arsenic or lead over the limit, yes, use bottled or a certified filter until a retest is clean. For iron, hardness, manganese or pH, no.
Does boiling make it safe?
Boiling kills bacteria and nothing else. It concentrates nitrate, arsenic and lead, so it makes those worse.