The impact of water hardness on urinary stone formation remains unclear, despite a weak correlation between water hardness and urinary calcium, magnesium, and citrate excretion. Tap water, however, can change urinary electrolytes in patients who form calcium stones.
Full Story:
https://pubmed.ncbi.nlm.nih.gov/12100915/
https://pubmed.ncbi.nlm.nih.gov/12100915/