Calcium Hardness in in vinyl pools?

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

Some of the SWCG folks can explain if you need calcium balance or not for an SWCG. However, for a vinyl pool, calcium is useless.

Pool manuals (Intex, as you point out) list standard water chemistry parameters without regard to the material of the pool surface. That is wrong, but if you decide to follow manufacturer's recommendations you'll just spend more money, but not do any harm. The saturation of pool water with calcium carbonate is to protect plaster surfaces (and grout in tile), but is not needed for vinyl nor fiberglass though having some calcium hardness for fiberglass can help to prevent cobalt staining.

Chem_geek is more detailed than me but I still don't know if it has any effect on SWCGs.

As far as I know, calcium is not needed for SWCGs and in fact a higher calcium level (or more technically a higher calcite saturation index) can lead to more calcium carbonate scaling in the SWCG. One generally targets a slightly negative saturation index in a plaster SWCG pool, but in a vinyl pool it can be more negative since there are no plaster surfaces to protect.

I would go with chem geek's chemistry any day unless one of our specialists on SWCG, like PoolSean ventures a different opinion.

Now I remember last year. I was maintaining the recommended calcium level in my Intex/SWG pool and I had a terrible time with calcium carbonate packing up the electrolysis cell. Had to soak it in HCl plus some scrapping with a thin piece of plastic to get the cell cleaned out three times. I wonder if those calcium carbonate deposits could short out the cell or at least reduce it's ability to create chlorine from chloride.

Richard

We've seen NO data indicating that you need to ADD calcium, for the benefit of an SWCG. But, as you've seen, even 'normal' levels of calcium increase SWCG maintenance.