Geological Survey Program fact sheet
Missouri Geological Survey Director: Carey Bridges, RG

The Missouri Department of Natural Resources performs water trace testing on drinking water wells to evaluate the quality of their construction or to find the source of a contaminant. To evaluate the integrity of a well casing seal, a small hole is dug close to the well. Dye is introduced into the ground through the hole. The dye will migrate down the borehole next to the well casing. If a satisfactory grout seal is present, the dye will be blocked from entering the well below the casing.

The department will provide the well owner four dye recovery packets made of activated charcoal to be used during the dye trace, along with pre-addressed, postage-paid envelopes to mail the samples to the department. Each charcoal packet should be placed (one per week) in the back of the toilet tank that is used most often. The toilet tank must be free of cleaners and disinfectants before the recovery packets are introduced, and throughout the duration of the test. It is also important to inform the department if you have a carbon filter or UV light in your water line.

During the four week dye trace test, the well owner should:

  • Remove the packet from the toilet tank at the end of each week. Excess water should be allowed to drain off the packet, but the packet should be left wet. It is important to individually package the recovery packet in a zip-lock bag and clearly label the bag with your name and the date the packet was removed.
  • Seal the zip-lock bag containing the packet, place it in the envelope provided by staff, and promptly mail it.
  • Place another packet in the toilet tank the same day the previous packet was removed. The new packet will remain in the toilet tank for one week.
  • Repeat this process until all four packets have been used.

Dyes most commonly used are rhodamine, which is red in color, and fluorescein, which is a lime-green color. In concentrations used for dye traces, both dyes are non-toxic and harmless, however, you may not want to use the water for drinking or washing if the dye is visible.

The department will analyze the packets as they are received and mail the well owner a notice of results after all packets have been analyzed. A positive result would indicate the presence of dye; a negative result would indicate no dye was present in the recovery packet. The presence of dye indicates potential problems with the well’s casing. If dye is detected, you will be contacted by department staff and provided further instructions. If you have questions during the dye trace, or if you see dye, please call the department. 

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

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