How To Measure TDS In Water & total dissolved solids

What is the TDS value?

TDS (total dissolved solids) is the abbreviation of total dissolved solids; the measurement unit is mg / L, which indicates how many mg of dissolved solids are dissolved in 1 liter of water. TDS refers to the total amount of all solutes in water, including both inorganic and organic matter.

The higher the TDS value, the more solutes in the water. The TDS value of pure water is 0. Generally, there are few soluble substances in pure water, So the value will be very low when tested with a TDS tester. However, there will be more soluble substances if the water is polluted, and the TDS value of the polluted water source will be very high.

The more conductive substances in water, the higher the conductivity and the higher the TDS value. At the same time, TDS will change with temperature. Some instruments are equipped with temperature sensors, which can automatically convert to a TDS value at 25 ℃.

TDS value indicates how many milligrams of total dissolved solids are in 1 liter of water. Still, it can not show other essential characteristics, such as the content of organic matter and bacteria in the water, nor the content of each inorganic salt ion.

Units related to measuring TDS

1) Milligrams (mg) / liter indicates how many milligrams of total dissolved solids are in 1 liter of water.

2) Ppm solution Ppm concentration unit. It refers to the milliliter of solute in 1 million milliliters of solution or indicates the gram of solute in 1 million grams of solution.

3) Conversion : 1mg / L = 1ppm

4) TDS is a similar relationship with conductivity. Sometimes TDS can also be used to represent conductivity. The relationship is 1ppm TDS = 2 μ S/cm, and the μ S / cm is the unit of conductivity.

The Digital TDS meter with LCD screen is convenient for reading and recording data and storing readings, which is used to test the purity of the filter water quality to check the performance of your water filter and the hardness (1 grain = 17 ppm). The TDS tester is recommended for every family to ensure that you always drink clean and safe water.

Is the lower the TDS value, the better?

TDS value and water quality are two different concepts. The higher the TDS value, the more impurities in the water. These impurities usually refer to the concentration of Ca2 +, Mg2 +, Na +, and K + plasma in the water, which cannot directly represent water quality.

Therefore, A high TDS value (more than 600) can indicate poor water quality, but a low TDS value does not mean good water quality. The quality of water quality depends on water quality indicators. Good drinking water quality should meet the water quality standards, such as microbial indicators, toxicological indicators, sensory properties, general chemical indicators, and radioactive indicators.

TDS is only one item of water quality indicators. The TDS value cannot show the concentration of heavy metal ions, the number of bacteria in the water, the nitrite concentration, and pesticide residues. Even if the concentration of bacteria and heavy metal ions in the water exceeds the standard, the TDS value will decrease as long as the concentration of dissolved Ca2 +, Mg2 +, Na +, and K + plasma in the water decreases. Therefore, the TDS value is one of the essential standards to consider for the quality of water quality.

What reason is the high number of TDS values?

The high TDS value indicates more dissolved minerals in the water, mainly Ca2 + and Mg2 +, which are beneficial to the body in reasonable conditions. China’s hygienic standard for drinking water stipulates that TDS ≤ 1000mg / L is qualified tap water.

If you have used the water purifier, but the TDS value of the filtered water is still high, it may be caused by the failure of the water purifier.

One is that the RO membrane itself has poor quality. In addition, when the water purifier is used for the first time, the RO membrane is soaked by the passing water, and a little residue left on the RO membrane during production is washed out, which will be fine in a few hours.

Another is that some carbon powder and inorganic minerals in the post-activated carbon filter element will also be brought out when the water purifier is used for the first time.

How to measure TDS at home

In general, we can use the TDS measuring meter to measure the TDS value in water at home. TDS (total dissolved solids) pen is used to test the content of soluble solids in water. Its principle is to indirectly reflect the TDS value by measuring the conductivity of water. In general, the more dissolved solids in the water, the greater the TDS value of the water, the better the conductivity of the water, and the greater the conductivity value.

How to use a TDS pen?

Open the TDS pen probe cover, press the on / off button, insert the TDS pen into the measured water, press the hold button after the value is stable, take out the TDS pen and read the value. After the test, wipe the TDS pen probe with dry paper.

Factors affecting the TDS value test

Total dissolved solids (TDS) refer to the total amount of all solutes in water. Its main components include calcium, magnesium, sodium, potassium ions and carbonate ions, hydrogen carbonate ions, chloride ions, sulfate ions, and nitrate ions; below are the main factors affecting TDS value:

1) Content of soluble solids in water;

2) Temperature of water body (the higher the temperature, the stronger the ionic activity);

3) Drop the electric field in the water body;

4) Velocity in water.

Therefore, It cannot use the TDS pen to measure high-temperature water bodies (such as hot boiled water), water bodies with significant shaking, and water bodies with high pollution concentrations.

How to use the TDS meter

TDS meter is an instrument for measuring TDS value in water, which can measure the ppm value of the inorganic or organic matter in the effluent. However, this is only an initial test, which cannot provide complete information about the content. If you want to know the content composition, it should be to use a higher accuracy instrument.

How to use it?

1)The water temperature during measurement should be about 25 ℃. The too high temperature will increase the TDS value and affect the correctness.

2)The value displayed on the LCD screen is the TDS value. If the TDS meter displays a number of 100, it represents the content of substances dissolved in water, and the total number of positive ions or negative ions is 100ppm (tolerance ± 5ppm). The higher the number, the more substances in the water.

3)Assuming that the average tap water in a place is about 250PPM and the RO pure water device can filter to less than 30ppm when the value exceeds 30ppm, it must consider replacing the RO filter membrane.

Pros and Cons

1) TDS can only measure conductive substances in water but can not measure bacteria, viruses, and other substances.

2)TDS is only a reference factor to show water quality.