A TDS meter estimates conductivity and is useful for tracking a stable system, particularly relative change across an RO membrane.
Evidence snapshot
- NHMRC (2025): The Australian Drinking Water Guidelines are a risk-management framework, not a single national pass/fail law. They separate health-based, aesthetic and operational considerations.
- NSF (2026): NSF standard numbers are not quality rankings. NSF/ANSI 42 covers stated aesthetic claims, 53 health-effect claims, 44 softeners, 55 UV and 58 point-of-use RO; the exact certified claim still has to be checked.
- US Geological Survey (2023): USGS explains that TDS and salinity depend on the analytical method. A handheld conductivity meter estimates ionic content; it does not identify which ions or non-ionic contaminants are present.
These figures and standards are reference points, not a diagnosis of one home. Local water data, premises plumbing, flow and maintenance determine how they apply.
What the first observation can tell you
Start with the property itself. Follow the claim through four steps: target, mechanism, operating conditions and verification. A material test does not automatically prove the finished system; plumbing approval does not prove contaminant reduction; a micron number does not describe dissolved chemistry. The evidence should match the exact question the household is asking.
A PFAS result is compound-specific and time-specific
It does not identify lead, PFAS, microbes or individual minerals, and a low number is not a safety certificate.
Use a PFAS method suitable for the named compounds and keep the reporting limit and units visible. Nanograms per litre and micrograms per litre differ by a factor of 1,000. A non-detect only means the named compound was below that method's reporting limit in that sample. Any reduction claim should name the exact model, flow, tested capacity and replacement point.
Use condition and service data, not colour alone
Use it as a trend tool alongside service records and targeted laboratory analysis when a specific contaminant matters.
Write the sample point, date, method, unit and laboratory reporting limit beside the result. A kitchen first-draw sample answers a different question from water collected after a two-minute flush. For a treatment check, use matched inlet and outlet samples and the same method. Do not use taste, colour or a TDS pen as a substitute for analysis of a named contaminant.
A practical household check
| Record | What to capture | Why it changes the decision |
|---|---|---|
| Claim | Write the exact target and unit | Prevents category errors |
| Conditions | Record flow, capacity and test basis | Tests relevance to the home |
| Verification | Choose a measure that matches the claim | Shows whether it worked |
Use the same notes when requesting more than one quote. Suppliers then have to answer the same water, flow and ownership brief rather than redefining the problem around their preferred product.
Where Water Analytics Australia fits
WAA's role is to turn the household brief into a proportionate design. That starts with source water, treatment goal, realistic peak flow, available pressure, installation access and the preferred service approach. Depending on the job, the answer may be whole-home staged treatment, point-of-use RO, the benchtop system or a combination. The written proposal should explain why each stage is present, the conditions behind each claim and what the customer will need to maintain.
Related WAA guides
- Why WAA Adds Minerals Back After Reverse Osmosis
- UV Water Treatment: Dose, Flow and the Conditions Required to Work
- WAA Full Home Water Refining Systems
Common questions
Does one specification prove the whole product claim?
No. A micron rating, material test, plumbing approval or TDS reading answers a limited question. Check the exact finished model, target, test method, flow and capacity.
What is the most useful measurement?
Use the measurement that matches the decision. Use a PFAS method suitable for the named compounds and keep the reporting limit and units visible. Nanograms per litre and micrograms per litre differ by a factor of 1,000. A non-detect only means the named compound was below that method's reporting limit in that sample. Any reduction claim should name the exact model, flow, tested capacity and replacement point.
What should WAA receive before recommending a system?
Provide the postcode, water source, household size, bathroom count, busiest-use pattern, observed issue, desired result and any laboratory report with its units and sample point.
Sources and further reading
- NHMRC: Australian Drinking Water Guidelines, version 4.0
- NSF: Standards for water treatment systems
- US Geological Survey: Salinity and total dissolved solids measurements for natural waters
The next useful step
Write down the source, the result you want, peak-use flow and the evidence already available. Then ask for a recommendation that gives every stage a defined job, states the operating assumptions and includes the service plan. That is enough detail to compare a WAA proposal with any alternative without relying on fear or brochure language.