PRESTIGE H2O / WATER, UNDERSTOOD
TDS and hardness measure different things
Hardness mainly reflects dissolved calcium and magnesium. Total dissolved solids, or TDS, describes a broader group of dissolved substances. The two measures can be related, but they are not interchangeable. A single TDS number cannot identify which substances are present or answer every water-quality question.
Give each result its own label
Record the parameter, units, sample point, date and method. Writing only a number such as 250 loses the context needed to interpret it. A result labeled TDS should not be entered as hardness when reviewing a softener proposal.
Match the measurement to the decision
Use a hardness result for a hardness question. Use a suitable laboratory analysis for a named substance. If you do not know what to test, explain the concern and water source to a qualified laboratory before taking the sample.
Compare before and after on the same basis
For a useful treatment check, record how and where both samples were taken. Ask which result the treatment is expected to change and how that change will be evaluated.
- Parameter and units on both results
- Sampling locations before and after treatment
- Date, method and any relevant operating conditions
- The system's documented treatment objective
Keep demonstrations in perspective
A meter demonstration can show a measurement changing. It does not establish every substance present, verify every product claim or replace the appropriate test. Request the test method and the conclusion it can support.
Questions and answers
Can I use a TDS result to size a water softener?
Do not substitute TDS for measured hardness. Ask the system designer for the hardness result and other inputs used in selection.
Does a low TDS result prove water is safe?
A single aggregate reading does not identify all possible concerns. Use appropriate testing for the question and follow your utility or public-health guidance when relevant.
What should I bring to a water-treatment discussion?
Bring the full report with units and methods, your water source, existing equipment details and the question you want answered. Avoid sending only a cropped number.