Get your water tested
A test shows your TDS and other problems, so you buy the right system.
What is TDS?
What the number on a TDS meter means, what it doesn’t tell you, and when it’s a reason to consider RO.
TDS stands for total dissolved solids: the minerals, salts and other substances dissolved in water. It is usually measured in milligrams per litre (mg/L), which is the same as parts per million (ppm), using a handheld TDS meter.
Why TDS matters
- Taste. Higher TDS makes water taste salty, bitter or heavy.
- Scale. Dissolved minerals leave white deposits in kettles, geysers, taps and pipes.
- Choosing a system. Only RO lowers TDS significantly. UV and UF don’t change it.
What TDS doesn’t tell you
A TDS meter measures the total amount dissolved, not what it is. Two samples with the same TDS can contain very different things. TDS also says nothing about bacteria or viruses. A low TDS reading doesn’t mean water is free of germs.
How TDS affects taste
The World Health Organization rates the taste of drinking water by its TDS level as follows.
| Feature | Taste rating | What it means for you |
|---|---|---|
| Under 300 mg/L | Excellent | No treatment needed for taste |
| 300 to 600 mg/L | Good | RO optional; depends on taste and use |
| 600 to 900 mg/L | Fair | Many people notice the taste; RO usually helps |
| 900 to 1,200 mg/L | Poor | RO is generally recommended for drinking water |
| Over 1,200 mg/L | Unacceptable | RO is needed for drinking water |
Source: World Health Organization, “Total dissolved solids in drinking-water”, background document for the WHO Guidelines for Drinking-water Quality (WHO/SDE/WSH/03.04/16). WHO sets no health-based limit for TDS itself; individual substances such as fluoride or nitrate have their own guideline values. Very low TDS water can taste flat.
Next steps
Compare RO, UV and UF
See which technology fits your water.