The PoolCalculator site says a number of things, not all of which agree with each other. It is a very useful tool -- if you know what you are doing. And, being based on Chem_Geek's analytical studies of pool chemistry, it's rather precise.

As it happened, I used the PoolCalculator site to run your numbers quickly, before I posted above.

But, the really important factor for you is, if your have a reasonable pH level (> 7.2) and *some* carbonate alkalinity and calcium present, any corrosion that does occur will take place very, very slowly. I've worked on a large indoor pool (> 150,000 gallons) that had not been drained for 10+ years, and had been serviced only with sodium hypochlorite and hand fed muriatic acid (= small amounts). PH levels on that pool ran a bit high (~7.8), but alkalinity and calcium ran a bit low (< 150 for each), even after 10 years of 'corroding' the plaster. The plaster itself was over 30 years old, and was stained, but not rough.

Keep in mind: to the best of my knowledge, NONE of the saturation indices have been validated by actual lab or field studies, as accurately reflecting the tendency of various waters to corrode or dissolve plaster.

Chasing numbers, whether it's done using Taylor's Dial-An-Index, the PoolCalculator, or with some other tool results in over-controlling your pool's chemistry, which translates into spending time and money unnecessarily.

Keep your pH up, and keep your TA and CH above 100, and you'll be fine. (Well, maybe not. Plaster quality may have deteriorated over the last 2 decades. This is a huge debate, with no final answers. Check out http://poolhelp.com/ for more info. But if you do have plaster problems, but have kept the numbers I indicated (pH>7.2; TA&CH>100), water chemistry is not the cause.)