Compact digital TDS meters, commonly known as water-testing pens, are increasingly finding their way into households in Islamabad as consumers show growing interest in checking drinking water quality and monitoring domestic filtration systems.
The pocket-sized devices can provide a Total Dissolved Solids reading within seconds and are being widely sold through online shopping platforms in Pakistan.
Basic models generally cost below Rs1,000 to Rs2,000, while more advanced multi-function devices are sold at higher prices.
The growing demand reflects the increasing use of filtration plants, bottled water and reverse-osmosis systems by households that want a convenient way to monitor water quality.
A TDS meter measures the estimated concentration of dissolved substances in water, including salts and minerals, and usually displays the result in parts per million.
Consumers use the device to compare water from different sources or monitor the performance of RO and filtration systems.
However, water-quality specialists caution that a TDS reading should not be confused with a complete test of drinking-water safety.
TDS indicates the amount of dissolved material but does not identify individual substances.
A handheld TDS meter cannot determine whether water contains bacteria, viruses, pesticides, arsenic, lead or other specific contaminants.
Director National Water Quality Laboratory at the Pakistan Council of Research in Water Resources, Saiqa Imran, said TDS is only one of several parameters used to assess water quality.
She said it cannot detect contaminants such as arsenic, nitrate, fluoride, heavy metals or disease-causing microorganisms.
Even if water has an ideal TDS level, it may still be unsafe if it contains harmful contaminants, she said.
She added that a TDS meter can be used as an initial screening tool to estimate dissolved salts and minerals, but laboratory testing is necessary to confirm whether drinking water is safe.
According to her, water may contain bacteria or viruses even when its TDS level remains within the permissible range.
Similarly, the presence of arsenic, nitrate or other chemical pollutants cannot be determined through TDS readings alone.
She said PCRWR recommends testing water for relevant parameters according to contamination risks in a particular area.
In Rawalpindi and Islamabad, nitrate testing can be important, while arsenic, fluoride and other parameters may require greater attention in areas where such contaminants are known to occur, she said.
The expert also cautioned consumers against assuming that extremely low TDS readings automatically mean the highest quality water.
She said domestic RO systems can remove dissolved minerals from water, and some consumers mistakenly treat very low TDS levels as proof of purity.
A TDS reading of 20, 30 or even 14 milligrams per litre should not automatically be considered a sign of superior drinking water, she added.
Saiqa Imran urged consumers using domestic filtration systems to understand what their equipment actually removes and to have their drinking water tested periodically by a qualified laboratory.
She said greater public awareness is needed because many consumers receive TDS meters along with RO systems without proper information about their limitations.
TDS, she said, is not the only criterion for determining water safety. It only shows the dissolved mineral and salt content.
She stressed that laboratory analysis remains essential to confirm whether water meets the relevant drinking water quality standards.
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