This is a naturally occurring acid found in all citrus fruits such as lemons, oranges, and grapefruits. Sourced in Thailand.
You can clean your water ionizer of all scale by doing a vinegar-wash or a citric acid wash.
Note: Wait to do a vinegar wash until it's about time to change the filter, otherwise it might taint the internal filters. In other words, when you're finished with the citric acid wash put a new filter in the machine.
1 Pound Bag
[Notes: 1. It may cause irritation if contacted by the skin in too high of a concentration. In this event, rinse with water. 2. This citric acid is food-grade.]