Description
The TDS Water Tester provides an estimated Total Dissolved Solids reading, together with Electrical Conductivity and water temperature measurements. Use it to establish a normal reading for a water source, compare suitable samples and monitor changes over time. Readings are most useful when taken under consistent conditions and interpreted alongside information about the water source and its intended use.
What Does a TDS Meter Measure?
Total Dissolved Solids, or TDS, describes dissolved material in water, including salts and minerals. A basic digital TDS meter measures electrical conductivity and applies a conversion factor to estimate TDS. It does not separately measure or identify every dissolved substance.
Common mineral ions, such as calcium, magnesium, sodium and chloride, contribute to conductivity. Different combinations of dissolved substances can produce different conductivity-based estimates.
Understanding TDS, EC and Temperature
- TDS is an estimated concentration, normally displayed in parts per million, or ppm.
- Electrical Conductivity, or EC, describes how readily water conducts an electrical current.
- Temperature affects conductivity and should be considered when comparing samples.
- For dilute water samples, 1 ppm is approximately equivalent to 1 milligram per litre (mg/L).
What Can You Use the Readings For?
- TDS and EC readings can help you:
- Establish a baseline for a particular water source.
- Compare samples collected under similar conditions.
- Notice changes that may warrant investigation.
- Monitor dissolved-solids reduction across reverse-osmosis or deionisation systems.
- A change in reading does not identify its cause. Similarly, a reduction after treatment does not prove that every contaminant has been removed.
Interpreting Drinking-Water Readings
The Australian Drinking Water Guidelines do not set a health-based limit for TDS itself. They recommend that TDS should not exceed 600 mg/L for good palatability.
The following categories describe taste acceptability—not drinking-water safety:
| TDS concentration | Palatability |
|---|---|
| Up to 600 mg/L | Good |
| Above 600–900 mg/L | Fair |
| Above 900–1,200 mg/L | Poor |
| Above 1,200 mg/L | Unacceptable for palatability |
Naturally occurring minerals can raise TDS. A low reading does not establish that water is free from harmful contaminants.
How to Use the TDS Water Tester
Follow the instructions supplied with your meter.
- Collect a sample in a clean container free from detergent or other residues.
- Remove the protective cap and switch on the meter.
- Place the sensing end into the sample to the immersion depth specified in the instructions. Keep the display and battery compartment dry.
- Allow the reading to stabilise before recording the value and measurement unit.
- Rinse the probe between different samples.
- After use, clean, dry and store the meter as directed in its instructions.
For meaningful comparisons, use the same meter, consistent sampling methods and similar sample temperatures.
Important Limitations
This meter does not:
Identify or quantify individual contaminants such as lead, arsenic, PFAS or pesticides.
Detect bacteria or establish microbiological safety.
Measure pH or provide a dedicated water-hardness result.
Confirm that a filter removes a particular contaminant.
Replace contaminant-specific testing or laboratory analysis.
If you suspect contamination, seek advice from your water provider or an appropriately accredited laboratory. Do not use a reassuring TDS number to dismiss an existing water-quality concern.
Care and Storage
Protect the meter from excessive heat, direct sunlight and moisture during storage. Do not immerse the complete device. Follow the model’s instructions for probe cleaning, calibration checks and battery replacement. Use an appropriate calibration solution if calibration is required.
For more information, please read the How to Use TDS Water Testers article.
FAQ's
A basic TDS meter estimates dissolved ionic content by measuring electrical conductivity and applying a conversion factor. This model also displays EC and water temperature. It does not identify which minerals or contaminants are present.
No. Harmful contaminants may be present without causing a meaningful increase in the reading. TDS does not establish microbiological safety or provide a complete chemical analysis. Use appropriate testing when drinking-water safety is the concern.
It cannot identify or provide a specific concentration for these contaminants. Some dissolved chemicals may contribute to conductivity, but the overall reading cannot tell you which substances caused it. Specific contaminants require suitable individual tests or laboratory analysis.
Australian guidance describes TDS up to 600 mg/L as good for palatability. For dilute water samples, this is approximately 600 ppm. This is a taste-related reference, not a safety threshold or a target that every water supply must reach.
It can help track dissolved-solids reduction in systems such as reverse osmosis and deionisation. Standard activated-carbon filters generally do not substantially reduce dissolved mineral ions, so an unchanged TDS reading does not establish that a carbon filter has failed. Follow the filter manufacturer’s maintenance instructions.
No. Hardness mainly relates to dissolved calcium and magnesium, while TDS includes a broader range of dissolved substances. pH measures acidity or alkalinity. A TDS reading cannot replace a dedicated hardness or pH test.
Possible reasons include changes in the water source, temperature, sample contamination, probe condition, calibration or different conversion factors. Repeat unexpected readings using a clean container and rinsed probe. Compare results under similar conditions and check the meter according to its instructions.
