The Black Berkey Red Food Coloring Test

The Black Berkey Red Food Coloring Test


The red food coloring MUST be artificial using reds FD&C 40 and/or 3.  The test only works with this artificial red dye, and the filters are designed to remove this out.  If the artificial red dye makes it through, then you have a defective filter.



  • We recommend this test be done upon first use, and then every three to six months to ensure the Black Berkey Filter Purification elements are working properly.
  • The red food coloring test is only designed for the Black Berkey Filter Purification elements and NOT for the ceramic or other filter elements that do not filter out food color. This test is also NOT recommended for the Sport Berkey water bottle.
  • Please make sure the food coloring is RED. Red food coloring (unlike the other colors) doesn’t have any minerals, so the element recognizes it as a contaminant.
  • The red food coloring test should be done after priming your Black Berkey Filter elements.


The Black Berkey red food coloring test provides the opportunity to showcase the impressive purification power of the Black Berkey elements. Many water filter companies make claims to their high quality, but Berkey water filters go one step further by making their lab test results public and presenting demonstrations such as the red food coloring test. While helpful for new customers to see the Black Berkey filters in action, it is invaluable for the existing customer base since it can be used at anytime during the life of the filters to ensure they are working to design specifications."Alternative" Filtered Water on Left; Black Berkey Filtered Water on Right


Whether the original black berkeys have been in operation for the past 3, 7, or 10 years, one can perform this test at anytime to see if it’s time for a replacement. We recommend customers place a cup underneath each filter as this will help isolate which filter is exhausted, and which is still purifying effectively.

With other water filters, the customer must assume their system is working to specifications or spend the time and money to perform water tests. This time lapse video shows how simple the red food coloring test can be done after priming your Black Berkey filters.


Performing the Red Food Coloring Test

  1. Start with an empty system (upper/lower chamber) and be sure to remove any PF-2 filters that may be attached.
  2. Check to make sure your black berkeys are installed with a tight seal and not allowing water to bypass the filter at the wingnut/washer connection. You’ll want to double check that these connections are tight.
  3. Place a glass in the lower chamber directly underneath each black berkey filter. So, 2 glasses if you are using 2 Black Berkey Filters.
  4. Next, fill your upper chamber with water and add 1 teaspoon of red food coloring for every gallon of water (only red please).
  5. After 5-10 minutes, look to see if any of the water in the glasses are red or have any pinkish tinge. If one does, then that particular filter above it is defective or saturated/exhausted.


Important Note For European Customers

Due to the fact that artificial red food color is banned in the UK/EU because of health concerns the instructions for the red food color test are not the same as the instructions you find on the American Berkey system assembly sheet. Do not follow the instructions on the enclosed assembly sheet.

UK/EU Red Food Coloring Test directions

Use only red food color sold in tiny 38-50ml bottles without any added glucose, sugars or thickening agents. These are available at all major supermarkets or Asian food shops. Do not use Dr. Oetker Gel Food Color Bright Red or any other gel-based food color.

Completely fill the upper chamber of a Travel, Light, Big or Royal Berkey with water, and then add a (1/4) quarter teaspoon or less of red food coloring to the upper chamber, stirring well. Add a (1/2) half teaspoon or less to the upper chamber of an Imperial or Crown Berkey. The water should have a slight pinkish tinge. If the food coloring is completely removed, your system is working properly. If not, make sure the wing nuts on the elements as well as the blocking plugs are securely tightened then re-run the test.

Once you have determined the water is running through clear for 5 -10 minutes the remainder of the colored water in the upper chamber can be discarded.

What Are Your Results?

As mentioned above, any red/pink in the filtered water indicates a need for filter replacement. If the water comes through clear, then you can be confident that the filters are performing as designed and removing contaminants from the water.

We recommend running this red food coloring test every 6 months. Besides checking that your filters are working as designed, it will also verify that the filter connections are sealed properly and everything is in working order.



  1. Are the wingnuts on securely? Please do not tighten the wing nuts using any tools; they should be hand tightened to a snug fit, but not more. If the wingnuts are on too tight, this could cause stripping on the threads of the stem, preventing a correct seal.
  2. Are you using actual “red food coloring” or another color or type of color? Red food coloring is the only type recommended for this test.
  3. Is the washer for the stem inside the upper chamber and is the wingnut secured at the bottom? If the washer is on the outside of the chamber with the wing nut, you will not have a proper seal, which will cause your system to fail the test. Place the washer on the inside of the upper chamber and re-run the test.
  4. Are the blocking plugs properly sealing the unused holes without elements? Are the plugs installed tight with a washer on each side? If the plugs are leaking, this will cause the system to fail the test. Tighten the plugs more securely and re-run the test.
  5. Are you re-testing an element that you think may have failed the test? If so, rinse off and re-prime the element first. Additionally, make sure you pour any excess water out of the bottom tank. Also, if you are using the lower chamber to catch water, run clean water through the spigot to clean it out as well. Now you are ready to repeat the test.