Natural water dissolves small amounts of rock as it travels — calcium, magnesium and others. That's why spring waters taste different from one another, and why some filters add minerals back.
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Background research
Hardness, explained
"Hard" water simply contains more dissolved calcium and magnesium. "Soft" water contains less. Neither term describes safety on its own.
Product information
How PristineHydro approaches it
PristineHydro's Water Revival Systems filter water first, then add minerals such as magnesium and calcium bicarbonate back in. Specifications are on each product page.