When I used the unit on my next client, black chunks immediately came out of the unit into the clear tap water. Why?
The unit was not cleaned in CLR to remove the grime and deposits on the rings from multiple uses. Re-clean the unit and there should not be any black chunks. Remember the first step in cleaning the unit is to rinse in running water. Shaking the unit under running water will help dislodge particles that form on the copper ring. Follow the other cleaning and sanitation procedure, but before using it on the next client, test the unit in a small bucket of water. The cleaning solution CLR will remove grime, but can take several hours, so leave the unit overnight in the CLR solution.
