THE MESS WITH THE TDS METER
THE MESS WITH THE TDS METER
Anyone interested in water filtration systems may meet sellers who use a measuring device to make a statement about water quality. Conductivity meters, so-called TDS meters, are used for this purpose. With this article we would like to inform about the informative value of these devices and put the measurement results in the right light.
First of all: a measuring device that indicates how good the water is by means of a simple number is unfortunately not available.
What is measured?
A) The sum of dissolved solids as TDS value
The TDS (Total Dissolved Solids) value indicates the sum of dissolved solids (e.g. minerals, salts, metals) in water. The common unit is mg/l (milligram per liter) or PPM (Parts Per Million). This means that at a value of 10 PPM per 1 million water molecules, there are about 10 molecules of dissolved solids. The measuring instruments measure the electrical conductivity of these substances and then convert them into PPM.
B) The resistance as µS value
The value Mikrosiemens (µS) is also used to measure the amount of dissolved conductive particles (e.g. minerals, salts, metals) in the water. In contrast to the TDS value, the electrical resistance in the water is measured, which allows conclusions to be drawn about the quantity of dissolved particles. Here, too, measurements are often made in PPM or the result is given directly in µS. Conversion to mg/l (2 µS/cm = 1 ppm = 1 mg/l).
What does the TSD/µs value say?
Both values, the µS-value and the TDS/PPM-value, exclusively say something about the number of dissolved solids in the water that are conductive. The higher the conductivity of the water, the higher the measured value. It 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. Especially residues of hormones, pesticides and fungicides do not conduct electricity and cannot be measured by a conductivity meter.
Measurement as a dubious sales ploy
Suppliers of osmosis plants often use a TDS measuring device to convince interested parties that their own water makes them ill. It is claimed that the test measures the pollutants present in the water. Only waters with a very low value ≤ 100 µS are health-promoting, so the statement. 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 with osmosis water is a low measured value. This is exclusively due to the fact that an osmosis water contains no or only a few minerals and is therefore no longer conductive. In this test it is not interesting which water is measured in comparison to the advertised water of the seller, it will lose this test, as long as it is not osmosis water or distilled water.
Fortunately, this sales pitch can easily be exposed by adding a pinch of the best salt to the low reading water presented. Even small amounts of salt can increase the value enormously. Afterwards, you can simply ask the salesman to explain what his meter actually measures. Whether the pinch of salt has made the water unhealthy or how the instrument distinguishes minerals from pollutants. We hope you enjoy the answers:)
WHO guidelines on drinking water
Statements that water with high TDS values is unhealthy are not confirmed by the WHO. In the WHO guidelines on drinking water, however, there is a separate document dealing with the TDS value (WHO/SDE/WSH/03.04/16, Total dissolved solids in Drinking-water, Background document for development of WHO Guidelines for Drinking-water Quality).
This document summarises that there are no reliable studies confirming the relationship between TDS levels and the health effects of water (1). In the following, water with too low a TDS value is described as often having an unpleasant taste and is just as problematic as water with a value above 2000µS (2).
Minerals as flavour carriers
Minerals belong in natural spring water and form its character; they give it its typical regional flavour. Whether a water has many or few minerals depends exclusively on the region and is not a sign of its quality. As with wine, there are waters fuller of character and lighter waters. Which water is preferred remains a question of personal taste.
Summary
The TDS value/µs-value cannot make any statement about whether a water is healthy or not. The conductivity alone is measured here. A water with many minerals has a higher TDS-value/µs-value compared to a water with few minerals. In nature, spring waters are found in varying mineral concentrations depending on their origin. Therefore, the conclusion that a high TDS value/µs value indicates low water quality is simply wrong. Studies which declare water with more minerals as unhealthy are not confirmed by the WHO. In our opinion a TDS meter within the consultation is a sales ploy by dubious sellers and should be treated with caution.
About the author:
Thomas Hartwig is a certified medical nutritionist and founder of the company Leogant. For many years he has been intensively involved with the element of water. He is a valued keynote speaker and guest on podcasts, where he shares his knowledge and experience. In his work he combines findings from natural science and medicine with philosophical approaches to contribute to a holistic water awareness.