Post your references. Sounds like the latest come-on to get A/G pool owners to buy calcium. I think it's probably garbage...You'd have to compare long-term pool usage of pools that have low calcium and those with high calcium. It would have to be over years and years, and a controlled study.

A study might be: recruit 500 homeowners around the country. Install new vinyl liners for all of them, then have half run with low calcium levels (what would that be? Below 100ppm?) and check their water weekly to ensure they were on-track. Have the other half run high levels--say 400ppm. Check 100 liners after 5 years (50 of each), 100 liners after 7 years, 10 years, 12 years, and 15 years.

With a protocol like that I would be less skeptical than I am now.

(this is how many clinical drug trial protocols are set up--that's how I know).