· by Michael Blair, Nashville's Water Filtration
Water treatment equipment is often sold on the strength of a demonstration rather than a test, and the demonstration is designed to sell. A real test answers two questions: is there anything in the water that matters for health, and what is in it that affects taste, fixtures and appliances. The answers are different on city water and on a well, and so is the test.
On city water
Metro Water Services publishes an annual water quality report that covers what leaves the treatment plant, and by the standards it is tested against, Nashville water is reliably within limits. What that report cannot cover is what happens between the main and your tap: the service line, the house plumbing and the fixtures. Lead from older solder and fixtures, copper from corrosion, and anything the water picks up standing in the pipes overnight are house-specific.
A city water household that wants to test should test at the tap after the water has stood for several hours, for lead and copper, and separately for hardness, chlorine and total dissolved solids to size any treatment for taste and scale. The hardness figure is what matters for a softener decision, and it is a number, not an impression.
On a well
Nobody tests a private well except the owner. The baseline for any well in Middle Tennessee is bacteria, coliform and E. coli, and nitrates, which are the tests that concern health directly. Our limestone geology adds hardness, often very high, and iron, manganese and sometimes sulfur, which are the tests that concern the fixtures and the smell. A well near agriculture or an old fuel tank has its own additions.
Bacteria should be tested annually and after any flooding, repair or change in taste. The full mineral panel is needed once to design treatment and again if something changes. Test in the wet season and the dry season if the water seems to vary, because shallow wells in karst ground do.
- Well, annually: total coliform, E. coli, nitrate
- Well, for treatment design: hardness, iron, manganese, pH, TDS, sulfide
- City, at the tap: lead, copper, hardness, chlorine
- Either, if there is a reason: pesticides, VOCs, radon, arsenic
Strips, kits and labs
Test strips and the free in-home tests offered by equipment dealers measure hardness, chlorine and pH reasonably and little else with any accuracy. They cannot detect bacteria, lead or nitrates at the levels that matter. A dealer test that turns the water an alarming color is a demonstration of precipitation, not a measurement of anything harmful.
A certified laboratory test is the only one that answers the health questions. Tennessee maintains a list of certified drinking water labs, and county health departments can point to them. The lab supplies bottles with instructions on how to collect the sample, and the collection method matters as much as the lab, particularly for bacteria and for lead.
Reading the result
A lab report lists each parameter, the result, and the standard it is compared to, usually the federal maximum contaminant level or a secondary standard for taste and appearance. Anything above a health-based limit needs treatment or a different source. Anything above a secondary standard is a nuisance, and whether to treat it is a preference.
Take the report, not the dealer summary of it, to the conversation about equipment. A softener sized from a real hardness number, a filter chosen for the actual iron level, and a disinfection system installed because coliform was found, are purchases that solve the problem. Equipment bought without the test often solves a different one.