What TDS meters actually measure in water and what they don't

TDS meters are used to test water quality, but what do they actually measure? Find out everything about how they work and what information they provide.

Key takeaways

• A TDS meter measures the total amount of dissolved solids in water.

• It does not indicate the specific type of dissolved solids.

• It does not measure other important water quality factors, such as pH, temperature, or bacteria.

• A high or low TDS level does not automatically mean the water is unhealthy or healthy.

• For a complete analysis, water testing in a laboratory is recommended.

How TDS meters work

TDS stands for "Total Dissolved Solids" — substances such as minerals, salts, metals, or other particles that dissolve in water. TDS meters are useful tools for better understanding the quality of the water you consume.

How does a TDS meter work? Simply put, it sends an electric current through the water. The resistance the current encounters depends on how many solids are dissolved in the liquid. The meter then converts this resistance into a TDS value.

There are several types of TDS meters, such as pen-style ones or those integrated into filtration systems (inline). Regardless of the model, the basic principle is the same.

What TDS meters don't measure

It is very important to understand what these devices can and cannot do. A TDS meter tells you how much is dissolved in the water, but not what exactly is dissolved. For example, it does not distinguish between beneficial salts and potentially harmful heavy metals.

In addition, TDS meters do not measure other essential water quality factors:

• pH: The acidity or alkalinity of the water.

• Temperature: How cold or warm the water is.

• Microorganisms: Bacteria, viruses, or other biological elements.

Interpreting TDS results

A TDS meter is not a definitive indicator of water safety. A high TDS level does not necessarily mean the water is bad, just as a low level does not guarantee it is perfect. For example, spring water, often considered high quality, can have a higher TDS level due to natural minerals.

On the other hand, distilled water, which has a very low TDS level (almost zero), is pure but lacks the minerals the body may need.

How to properly test your water quality

If you truly want to know what your water contains and whether it is safe for consumption, the best method is to use a water testing laboratory. Professional equipment can perform complete analyses, identifying the exact substances present and their concentrations, including contaminants that are not detected by a TDS meter.

At FILTRO, we offer several informative water analysis packages. The testing process is simple. Order the desired package online, collect the sample according to the instructions, and we will send a courier to pick it up from your location.
1. Essential water analysis package, 10 physico-chemical parameters, sample collection by courier
2. Advanced water analysis package, 11 physico-chemical parameters, sample collection by courier
3. Extended water analysis package, 14 physico-chemical parameters, sample collection by courier

So, a TDS meter can be a useful first step to get an idea about your water, but it does not replace a professional analysis. If you have questions about TDS or how to test your water, feel free to leave them in the comments!

Frequently asked questions

Q: What does a TDS meter actually measure?
A: A TDS meter measures the total amount of dissolved solids in water (Total Dissolved Solids), such as minerals, salts, or metals. It indicates their total value, usually expressed in ppm (parts per million), but does not identify the exact type of substances present.

Q: How does a TDS meter work?
A: The meter sends an electric current through the water and measures its conductivity. The more dissolved substances there are, the better the water conducts electricity. Based on the resistance encountered, the device calculates and displays the TDS value.

Q: Does a high TDS level mean the water is dangerous?
A: Not necessarily. A high TDS level may indicate a high concentration of natural minerals, as is the case with spring water. Likewise, a very low level does not guarantee the water is perfect, as TDS does not detect bacteria, viruses, or certain specific chemical substances.

Q: What can't a TDS meter measure?
A: A TDS meter does not indicate the type of dissolved solids and does not measure pH, temperature, or the presence of microorganisms. It also cannot differentiate between beneficial substances and potentially harmful contaminants.

Q: Is a TDS meter sufficient to evaluate water quality?
A: No. A TDS meter can be a first step for a quick assessment, but for a complete analysis it is recommended to have the water tested in a specialized laboratory, where physico-chemical parameters and specific contaminants can be identified.