These and similar questions reach us again and again. It is assumed that an electrical TDS meter can make reliable statements about the quality of drinking water for about 25€. The TDS (Total Dissolved Solids) value indicates the sum of dissolved solids (e.g. minerals, salts, metals) in water. The unit commonly used is mg/l (milligram per litre) or PPM (Parts Per Million). The device displays the electrical resistance either directly in microsiemens (µS) or converts it into the PPM value (2 µS/cm = 1 ppm). Both values only say something about the number of dissolved solids in water that are conductive. The higher the conductivity of the water, the higher the measured value. This is not a chemical analysis of the water according to its exact ingredients. Therefore, these are purely quantitative measurements that say nothing about the quality of the water. Whether harmless sodium, calcium, magnesium or e.g. toxic arsenic, lead or uranium makes a difference for your body. Especially residues of hormones, pesticides and fungicides do not conduct electricity and cannot be measured by a conductivity meter! Crush a paracetamol tablet once and stir it into a glass of water. You will not measure any difference, even though the water is now extremely contaminated with drug residues. On the other hand, just a small pinch of table salt in a glass of water will sound the alarm wrongly.
Dubious sales statements
Suppliers of osmosis plants often use a TDS meter to convince prospective customers that their own tap water makes them ill. It is claimed that the device measures the pollutants in the water. Only water with a very low value below 100 µS is said to be beneficial to health. The digital measured value is therefore a guide value for the quality of the water. However, the measured value only indicates how conductive the water is. Only osmosis water has a low conductivity value. This is solely due to the fact that osmosis water contains no or very few minerals and is therefore no longer conductive. In the meantime, some manufacturers of osmosis systems have recognised that "empty" water tastes unpleasant and is not beneficial to health. Therefore, most of them have now built in a remineralisation stage. But if this would work, the conductivity would be as high as before.
Minerals are important flavour carriers
Minerals belong in natural spring water and form its character. They give the water its typical regional flavour. Whether a water contains many or few minerals depends exclusively on the region and is not a sign of its quality. There are waters full of character and lighter waters.
What does the German Drinking Water Ordinance say about the conductivity value?
In the worldwide very strict German Drinking Water Ordinance (TrinkwV), the electrical conductance is only mentioned in connection with the corrosion of the pipes. If the mineral content is too high, a current can flow between noble and base metals in the pipes and cause them to rust.
What does the WHO say about the guide value?
Statements that water with high TDS levels is unhealthy are not confirmed by the WHO. In the WHO guidelines (WHO/SDE/WSH/03.04/16, Total dissolved solids in Drinking-water, Background document for development of WHO Guidelines for Drinking-water Quality) it is summarised that there are no reliable studies that confirm the relationship between the TDS value and the health effects of water. Water with too low a TDS value is often described as having an unpleasant taste and is just as problematic as water with a value above 2,000 µS.
CONCLUSION: The TDS conductance in PPM or Mikrosiemens µs can NOT make a statement about whether a water is healthy or not! For this reason we do not give any information on the conductance.