I seer that adding calcium to concrete pools helps to prevent concrete erosion but isn't needed for vinyl pools.

Swimming Pool Secret #3
"If you like contributing to your dealer's vacation fund, stop reading now. If you keep reading, you're likely to discover just how useless adding calcium to a liner pool is!"

Yet Intex seems to contradict this. They recommend 200 - 400 ppm CH in their SWG manual. All they sell is vinyl pools as far as I can find.

Does anyone have any knowledge about where this difference in opinion came from?

Richard