What Does TDS in Water Mean?
TDS in water stands for Total Dissolved Solids. It is the total amount of everything dissolved in water that is not visible to the naked eye.
TDS mainly includes minerals and salts along with other organic material. One cannot see these dissolved materials, which is why it is possible for visibly clear water to have abnormal amounts of TDS.
What Elements Make Up TDS?
Most of the total dissolved solids are common minerals and salts, such as:
These minerals come from rock and soil as water travels underground collecting them. Most of these minerals are harmless in normal quantities. Sometimes, while on its way to the surface, water also collects unwanted elements such as nitrate. TDS gives a measure of everything at once without quantifying their amounts separately.
How Do We Measure TDS?
Most commonly used TDS meters do not directly measure the dissolved solids in water. They measure the amount of electrical current that the water allows to pass through.
The minerals and salts present in water allow electricity conduction. The TDS meter measures the electrical conductivity and converts this into an estimated TDS reading. Because this is an estimate:
- Different meters can show slightly different TDS readings.
- The temperature of the water and the calibration of the meter directly affect the results.
- A TDS meter cannot tell us which specific minerals are present; it only provides an overall aggregate value.
Limitations of a TDS Meter
It is important to discuss the limitations of a TDS meter in order to avoid mistakes in making assumptions about water:
A TDS reading does not say anything about whether water is free of germs. Water with low amounts of TDS may still carry bacteria or cysts due to poor handling, plumbing, or storage.
It does not detect whether a specific harmful element (such as lead, arsenic, or pesticides) is present in small, dangerous traces.
A TDS reading does not imply whether water is safe for drinking. A high TDS value does not necessarily mean water is unsafe; it mostly indicates a large amount of dissolved minerals affecting taste.
What Does the World Health Organization (WHO) Say?
The World Health Organization does not have a strict health-based guideline regarding the TDS value of water. However, it does outline the taste profile of drinking water based on TDS levels:
| TDS Level (mg/L or ppm) | Consumer Palatability & Taste |
|---|---|
| Below 600 ppm | Good • Refreshing and balanced taste |
| 600 – 1,000 ppm | Fair • Minerals become noticeable |
| Above 1,000 ppm | Unpleasant • Saline or mineral-heavy palate |
Reference: World Health Organization Total Dissolved Solids Background Document.
TDS at a Mr. RO Water Plant
At a Mr. RO water plant, TDS value is made useful by taking two readings: one at the feed water inlet, and the other after the RO membrane (product water). The difference between the two values indicates how well the membrane is performing:
For example, if your feed water remains unchanged but the salt rejection percentage steadily declines, your RO membranes need chemical cleaning, flush attention, or replacement.
Is a Low TDS Reading Better?
A low TDS value does not mean a better reading. Reverse osmosis can bring the TDS level extremely low. However, water with an overly low concentration of minerals feels flat, empty, and acidic.
That is why professional plants add a controlled amount of minerals such as Sodium, Calcium, and Magnesium after the water passes through the RO membrane.
Considering conditions across Pakistan, especially in metropolitan areas like Lahore, the importance of water filtration has increased significantly. Along with that, the vitality of utilizing certified minerals like sodium, calcium, and magnesium has become prominent.
The challenge of buying effective, reliable, and original minerals remains critical. Minerals by Mr. RO solves this challenge with certified food-grade compounds.
Looking for Certified Water Minerals?
Explore our calibrated 1kg, 2kg, and 5kg packs of Calcium Chloride, Magnesium Sulphate, and Sodium Bicarbonate.
How to Use TDS in a Better Way
Use the Same Meter: Always use the same meter when comparing relative TDS levels across tests.
Rinse the Probe: Rinse sensors with clean water and test samples at similar temperatures.
Recheck Calibration: Regularly verify meter calibration against buffer reference solutions.
Evaluate Holistically: Treat TDS as one single parameter alongside biological testing and pH.
Frequently Asked Questions
Is zero TDS level best for water?
No. Zero TDS makes water taste flat and acidic. It does not dictate or guarantee total water quality.
Is high TDS level considered bad?
Not automatically. High TDS depends entirely on what is dissolved. Only laboratory chemical testing can specify what elements are present.
Can boiling the water lower the TDS levels?
No. Boiling only destroys bacteria and germs; it cannot eliminate dissolved mineral solids. Boiling actually increases measured TDS slightly because water steam evaporates while minerals stay behind.
Does a TDS meter tell us if the water is safe?
No. It is one indicator among many. While it effectively guides water taste and membrane performance, it cannot verify biological purity.