What is the TDS indicator on the water purifier?

TDS is the total dissolved solids present in a given amount of water. Refer to the following article to better understand the TSD index on the water purifier, what is clean water and how to check the quality of the water in use!

Domestic TDS Indexes

TDS is measured in mg/l (milligram/litter) or ppm (part per million): 1 mg/l = 1 ppm.

According to the current regulations of WHO (World Health Organization), US EPA (US Environmental Protection Agency) and Vietnam:

– The lower the TDS index, the 5 ppm or less is considered pure water, without dissolved solids . With this water source, when used, it only meets the needs of providing clean water for the body without providing or adding minerals.

– The larger the TDS , the higher the concentration of dissolved solids in the water . Because there are beneficial and harmful solids in the mix, a higher TDS is not necessarily harmful.

– If using hard water to eat and drink continuously for a long time, it can lead to a number of diseases for the body such as: kidney stones or blockage of arteries and veins, which is dangerous to health.

– If used to prepare drugs, it will cause precipitation, change the composition of the drug . Using water for cooking will make food difficult to cook.

– When washing with hard water, soap is wasted because Ca2+ precipitates the acid base in the soap and makes the soap not foam, making it difficult for clothes to be washed.

– Industrial equipment when using hard water will have a surface state of residue , which will affect the performance of the device for a long time.

What is clean water, safe water for health?

– To assess whether the water is clean or not, the Ministry of Health has issued the QCVN 01:2009/BYT standard. In which, there are 109 indicators of permissible concentrations of substances in water such as color, taste, turbidity, pH, alkalinity – hardness, total dissolved solids, inorganic and organic contents. mechanical (aluminum, iron, manganese, arsenic, cadmium, chromium, copper, lead, zinc, nickel,…), radiation levels, microorganisms (coliform, ecocol, …)…

– Clean water is water with a measurement index below the concentration of substances allowed by the Ministry of Health as promulgated according to Circular No. 04/2009/TT – BYT dated June 17, 2009.

In addition, the ministry also added 21 chemical criteria and 5 microbiological criteria according to QCVN 06-1: 2010/BYT to achieve more standards of clean water that can be drunk directly without needing to boil.

Check water quality with TDS test pen and electrolysis pen

• The TDS index tester with the working principle is based on the conductivity of the water source , to determine the content of solid ions as well as minerals and metals present in the water.
• The electrolytic pen works with two aluminum electrodes, two iron electrodes. If using a pen with mains electricity (220V AC), the DC voltage between the aluminum pole and the iron pole is 220V. When electrolyzing water, each pair of electrodes is dipped into a glass.

When current flows between the electrodes, it carries metal ions in the water and causes chemical reactions with the aluminum and iron electrodes, creating different colors. Based on this color we can detect some metal ions and impurities in water such as:

+ Only effervescent, no precipitate, no clouding: Pure water

+ Only effervescent, creating white precipitate: Contains Ca 2+, Ag+…

+ Red-brown color, with scum: Contains many Fe 2+, Fe 3+ ions…

+ Blue color, with precipitate: Contains a lot of Cu 2+…

+ Light gray color: Contains Pb 2+, Hg…

+ Dark brown color: Contains Mn 2+…

Check the TDS index in the water after filtration of the RO water purifier

RO water purifier includes a system of 5 – 10 filtration levels, in which water will pass through the initial basic filtration levels to remove impurities, dirt, mud … of large size. This water is then further filtered through an RO membrane, which is a filter with 0.0001 micrometer-sized filters (about 1/10,000th the diameter of a human hair).

With this filter size, most chemical components, heavy metals, and bacteria cannot pass through the RO membrane, so that the filtered output water is considered pure water.

To check the TDS index after going through a conventional RO purifier with a TDS test pen, it will be checked at 2 locations:

– Get water at the pressure tank , which is the source of water after going through the RO membrane. The standard of drinking water at this location is around 20 ppm which is safe for the body.

– Get water at pure tap water . If your water purifier has beneficial mineral levels, the TDS in this position will be different from the previous test. If the TDS here is higher, you can still safely use drinking water, because the water is supplemented with beneficial ions.

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Water purifier with display of TDS

On the market, there are a number of RO water purifiers with a display screen of water quality – TDS index, informing users of the exact TDS index of the filtered water source.

Thanks to this parameter, users will assess the safety of water used directly at home.

Through the basic information obtained about the TDS index and its application on home water purifiers, hopefully it will be useful for users to check and determine the quality of water used daily through the water purifier, for the safety and health benefits of the whole family.