Excerpt from their website: "The new formula incorporates an ingredient, sodium polyacrylate, that binds to certain minerals that are in the water supply preventing them from depositing on your clothes."
"Sodium polyacrylate" meant nothing to me, so after a little Googling, one website says it's used in crystal form to absorb liquid in disposable diapers, and also used as a "plant gel" to hold water in-lieu-of soil.
This doesn't directly answer your question, but certainly suggests further investigation is warranted before continued use in drinking water.
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"Things that have never happened before happen all the time." — Scott Sagan, The Limits of Safety