TDS meter
Have you ever wondered how to measure the quality of your drinking water? Many people rely on a TDS meter to check the purity of their water, but there are many misconceptions about what this meter actually measures. I recently listened to an interview with a water expert on the radio, and while his knowledge was impressive, I noticed some misleading statements about using a TDS meter.
In this blog, I explain exactly what a TDS meter measures, why it's important to understand what it doesn't detect, and how to determine the true quality of your water.
What is a TDS meter and how does it work?
A TDS meter is basically a conductivity meter that measures the amount of dissolved ions in water. This is done by applying an electrical voltage between two or more electrodes. Positively charged ions, such as minerals and trace elements (e.g., calcium, magnesium, sodium, zinc and iron), move to the negatively charged electrode. At the same time, negatively charged ions, such as chloride, sulfate, sulfite and fluoride, move toward the positively charged electrode.
The movement of these ions creates an electric current. The TDS meter then measures how much current flows between the electrodes, giving insight into the amount of dissolved ions in the liquid. The result is displayed in ppm (parts per million).
When measuring pure water (H2O), the meter reads 0. This often raises the question, "If a TDS meter indicates a value higher than 0, does that mean it contains contaminants?" The answer is: no. A higher value only means that other dissolved substances, such as minerals, are present in addition to water.
In a video, I demonstrate this by adding acetone, benzene and brake cleaner to demineralized water. The TDS value remains low until I add minerals, at which point the TDS value rises. This shows that pure water does not occur in nature, and without minerals and trace elements flora and fauna could not survive.
What does a TDS meter actually measure?
It is essential to understand what a TDS meter does not measure. These meters detect only mobile charged ions, such as minerals and trace elements, but cannot measure neutral (uncharged) compounds. This means that substances such as sugar, alcohol, and many organic compounds - including chemicals, drugs, hormones, pesticides and their residues - will not be detected by a TDS meter. Non-ionized forms of substances such as silica, ammonia, and carbon dioxide are also outside the measurement range.
In addition, TDS meters do not measure macroscopic particles because they are too large to move through the meter's electric fields. This means that contaminants such as rust particles, bacteria, viruses and microplastics cannot be detected by a TDS meter.
Certain pollutants, such as PFAS (used in the GenX process), Chromium-6 and lead, often occur in extremely low concentrations (parts per billion or even smaller). These substances are therefore not detectable with a TDS meter, meaning that a low TDS value does not necessarily indicate clean water.
The term "total dissolved solids" is actually misleading. A better description would be that a TDS meter measures the total amount of charged ions. For example, a TDS reading of 8 may mean that virtually all minerals and trace elements have been removed from the water, but the water may still be contaminated with hazardous substances such as drugs, pesticides, GenX, bacteria and microplastics.
How can the quality of filtered water be determined?
With a TDS meter, you can NOT test the quality of filtered water. A TDS meter drinking water only measures dissolved ions, but leaves out major contaminants such as chemicals and bacteria. This can only be tested in a laboratory. Always ask for test reports from a water filter provider. Don't be fooled by statements such as: "Our filter contains activated carbon, so it takes out all the harmful substances." If it were that simple, drinking water companies would have removed all those substances long ago. What matters is the combination of filters and the time the water is in contact with the filter material. With many filters, the water flows through too quickly, but Aqualine systems filter slowly, averaging 1.5 liters per hour, for better results.
Our Aqualine filters are proven to remove the PF(O)AS from the water used in the GenX process. In addition, we remove a large number of other substances from the water.
The role of minerals in filtered water and the TDS value
Our Aqualine filters have a higher TDS and that's because we add minerals to the filtered water. If you choose the alkaline version, the included pH ring also releases some additional minerals and magnesium to raise the pH of the water to slightly alkaline water.
Some providers indicate that we should only drink H2O. So this is water in its purest form. So this is water that is also free of minerals and trace elements. For as long as humanity has existed we have been drinking water from springs and rivers. Depending on the soil conditions, this water is rich in all kinds of different minerals and trace elements. Flowers and plants cannot grow without minerals.
That we want to purify the water from pollution I understand, but why do we want to filter the natural elements out of the water?
Aqualine water filter systems mimic nature. We remove the contamination as much as possible with natural materials, add some minerals and trace elements and vitalize the water while draining. This vitalization also happens in nature. This effect is not available with most water filter systems offered.
When do you use a TDS meter?
A TDS meter is useful for measuring the concentration of dissolved substances in water, such as in aquariums to ensure water quality for fish or in hydroponics for optimal nutrient balance. It can also help check water filters and self-filtered drinking water, although it does not detect contaminants such as chemicals or bacteria. It provides useful information, but is not a good solution for measuring drinking water quality.