What TDS Level Requires RO?

What a TDS meter tells you

A handheld meter estimates total dissolved solids from electrical conductivity, commonly displayed in ppm. It does not identify individual substances. Two samples with the same reading can contain very different mixtures, and the meter does not test for bacteria or viruses.

Why a range is not a safety decision

WHO does not establish a health-based guideline value for TDS itself. Taste and acceptability can change with dissolved substances, but neither a low reading nor pleasant taste establishes safety. Specific chemical and microbial results need to be assessed separately.

• Low TDS can coexist with microbial contamination.
• High TDS does not tell you which dissolved substances need treatment.
• RO may be relevant to a specific dissolved contaminant even when total TDS is not high.

How to use readings during a consultation

• Record the water source and where the sample was taken.
• Follow the meter instructions and record the date and reading.
• Share an appropriate laboratory report if contamination is suspected.
• Ask which verified treatment targets the identified concern.

After installation

Comparing inlet and output readings under similar conditions can help a technician investigate changes in RO performance. It is an operational indicator, not proof of safe drinking water or conclusive evidence that the membrane needs replacement.