TDS Meter FAQs

No. A TDS meter is a broad test used to determine levels of Total Dissolved Solids (TDS) in a liquid, whether good or bad. This would include the content of all inorganic and organic substances in molecular, ionized, or micro-granular (colloidal sol) suspended form. Common TDS substances include calcium, phosphates, nitrates, sodium, potassium, and chloride. Water that is completely void of any TDS is often described as having a flat, unpleasant taste, and would be lacking in important, healthy minerals your body needs. To know for sure whether or not your water filter is functioning correctly, you would need a test that focuses specifically on the contaminants the filter claims to remove, such as chlorine or lead. A TDS meter has too broad of a test range to give an accurate reading for the functionality of a water filter.

Certain types of filter media can result in a higher TDS reading after the water has been filtered. For example, with a carbon filter, the granulated activated carbon (GAC) coconut shell media tends to flake off, particularly at first use. The tiny, harmless carbon particles would then result in a higher TDS reading. After being properly flushed, the amount of carbon residue will decrease, but carbon filters always tend to result in higher TDS readings. In general, a TDS meter is not a good indicator of how well your water filter is working.

Many users may confuse the TDS meter as an effective way to test the performance of water treatment devices such as carbon filters, but that is not its intended purpose. A TDS meter is meant to measure the performance of very aggressive forms of filtration such as reverse osmosis and deionization. Filters like carbon filters and other inline filters will not dramatically lower TDS, but that is not their primary intended purpose. Where an RO membrane physically filters water down to 0.0001 micron, reducing practically all organic and inorganic particles present in water via mechanical filtration and thus yielding a very low "total dissolved solids" reading, a carbon filter filters out chlorine and other unwanted chemical contaminants through a process called adsorption. As such, a carbon filter's performance cannot be measured by a TDS meter because the impurities being removed are not dissolved solids, but chemical contaminants and volatile organic compounds. It is also worth noting that most TDS is not harmful and includes healthy minerals such as calcium and potassium, and the removal of TDS is generally neither necessary, nor desirable from most water supplies in the United States, including even from most campgrounds.