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Berkey Water Filters and TDS Readings

Many customers experience an increase in TDS readings during the initial break-in of the black berkey filters. Since we often get the question asking why this occurs, we decided to provide a more in-depth and scientific explanation.

Total dissolved solids (TDS) is the combination of all inorganic and organic contents contained in a liquid having a molecular, ionized, or micro-granular (colloidal sol) dissolved form. Total dissolved solids are normally only discussed for freshwater systems, since salinity comprises some of the ions constituting the definition of TDS. The principal application of TDS is in the study of water quality for streams, rivers and lakes, although TDS is not generally considered as a primary pollutant (e.g. it is not deemed to be associated with health effects), but it is rather used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of presence of a broad array of chemical and mineral contaminants that could be in water.


The Black Berkey element formula utilizes two ingredients that will add TDS to any water passing through the elements. Firstly, all filters that utilize any form of carbon in their formulation increase TDS, as carbon fines (invisible) will attach to water as it passes through the element. Many filters utilize nano-sized particulate in high quality carbon micro fines to create the outer "mean porosity" and interior tortuosity of the block or cross section of the filter elements. Several tests are performed on automated lines to insure exact porosity and final destructive tests determine the durability of the element. Two of these tests purge or remove most of these fines, which enable the flow of water through the element through open micropores. Additional fines are removed during purging, however there may still be some non-harmful nano size carbon micro fines present in the water after filtration.

The Drinking Water Regulations in the United States typically regulate TDS not to discover micro fines of carbon but rather unsuspecting organic and inorganic chemicals along with other micro pollutants. TDS cannot help define any one category of constituent detected in liquids or water, only the presence of a total amount of dissolved solids, whether harmful or not.

The second and probably most common reason for increased TDS in water run through a Black Berkey element is the ion exchange media. Ions are a form of TDS, and as indicated above, are found in sea water and in water subject to any substance that ionizes liquids and or air (air ionizers) etc. There are millions of ions in the air and they are essential to life. Ions do not comprise a health risk but rather, a health benefit. While TDS will likely be on the very low should continue to exist for the life of the filter.

Another simple test would be to test water before and after a pass through an inexpensive Carafe style water filter. You will observe the same increase in TDS.

We hope this helps with any questions or concerns. TDS is actually the least effective type of test to determine whether water is suitable to drink. In actuality, most involved in this type of discussion are unaware and don't understand the variety of sciences concerning water filtration. Typically this type of discussion arises from those promoting the use of RO and Distillation methods, which drastically reduce TDS. Unfortunately, such water is acidic, is never found in nature, and therefore can confuse the body, which typically will attempt to re-mineralize such water by robbing essential minerals from the body. For more information on this issue please see the below references:

4 thoughts on “Berkey Water Filters and TDS Readings”

  • Trisha Smet

    I bought my mother a Berkey unit and she was thrilled to be able to drink her tap water. She replaced her filters in March 2017. However, she was just told, based on a water filtration company that offered a FREE water analysis that her water has a TDS of 700. She was told that this level is deemed unsafe for human consumption.
    Of course, she is alarmed. I've entered her email address so you can inform her directly.
    Please advise.

    • Dan DeBaun

      Hi Trisha -

      The TDS meter only measures dissolved solids such as heavy metals and beneficial minerals, NOT chemicals, bacteria, etc... Without a detailed breakdown of what the levels of each dissolved solid in that test read out as, this would not be an accurate statement from the water filtration company you worked with. In other words that TDS reading of 700 could be all potassium, and thus WOULD be safe for human consumption. The Berkey will remove the heavy metals from the water, and not the beneficial minerals, so it is likely that this reading represents all beneficial minerals. Again, being safe for human consumption. If there is still concern from you or your mother, I recommend getting a detailed reading of what each dissolved solids level reads out at.


  • Zasele

    I just used a TDS EZ tester on my Big Berkey filter water and it reads 260-262. I measured my tap water and it's 255. How's that even possible when the filter is suppose to take away, not add to the water. What's going on?

    • Dan DeBaun

      Hi Zasele -

      A TDS meter measures only Total Dissolved Solids or minerals; dissolved solids are simply dissolved minerals in an ionic form. A TDS meter does not measure the amount of biological and chemical contaminates. Black Berkey elements are designed to leave in your water the healthful and beneficial minerals and to extract only the unwanted heavy metals such as lead and mercury as well as sedimentary minerals such as iron oxide and aluminum. Therefore, your TDS reading will not change much unless you have a significant amount of heavy metals or sedimentary minerals in your water. When it comes in a little higher, this is a result of either the dust wash off from the break in of the filters, or you have some calcium or other mineral deposits in the lower chamber, that are increasing the post filtration mineral content reading on that meter.

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