1. Confirm sample identity
Check source, tap or sampling point, date, collection method, preservation, laboratory, report number and intended use. A result from a kitchen tap is not automatically a raw-well result.
2. Separate result, method and comparison value
The result is the measured or reported value. The method explains how it was determined. A guideline, screening value or legal limit belongs to a named jurisdiction and use; these columns are not interchangeable.
3. Read units before numbers
mg/L, µg/L, NTU, CFU/100 mL, conductivity and mg/L as CaCO₃ describe different quantities. A hardness number in mg/L as CaCO₃ cannot be compared directly with an elemental calcium result.
4. Understand qualifiers
ND means not detected at the stated reporting or detection limit, not proven absent. “<” means below the stated quantitation threshold; “>” means above the reportable range and can require dilution or retesting.
5. Group physical and operational indicators
pH, alkalinity, hardness, conductivity, TDS, turbidity, color and odor help explain corrosion, scaling, particles or aesthetic concerns, but indicators alone do not prove toxic chemicals or pathogens.
6. Review common inorganic results
Iron and manganese can affect color, staining and treatment. Nitrate, nitrite, chloride and sulfate have different health, taste, corrosion and source implications. Use the applicable health authority to interpret elevated results.
7. Treat microbiology separately
Total coliforms and other indicator or pathogen results require the laboratory’s method, sample validity and local public-health response. Do not use appearance or a single household filter to override a positive result.
8. Compare source responsibility
A public-supply customer should review the utility report and contact the utility for sudden changes. A private-well owner generally arranges testing and corrective action under local guidance. Rainwater and surface water require source- and use-specific assessment.
9. Repeat or expand testing
Retest unexpected or health-significant results as directed, investigate changed source conditions and add locally relevant analytes. One normal sample does not guarantee future quality.
10. Move to treatment only after an objective
Define which verified parameter must change, for which use, at what peak flow and with what follow-up verification. Then use the treatment selector and certified product claims.
Worked example
A report shows hardness 220 mg/L as CaCO₃, iron 0.8 mg/L, turbidity 2.1 NTU and microbiology marked ND with a reporting limit. Do not read this as “safe” or “needs only a softener.” Confirm the microbiology method/limit, investigate iron and turbidity pretreatment, then size any softener from actual usable capacity and peak flow.
Sources
- U.S. EPA — Protect Your Home’s Water
- U.S. CDC — Guidelines for Testing Well Water
- U.S. Geological Survey — Water Science Glossary
- World Health Organization — Guidelines for Drinking-water Quality