Calcium for metal

[chem geek]

Thanks Richard for clearing this up. I am still hearing different takes on if you should use calcium in a fiberglass pool. Now I can see that it really isn't necessary.

Marie,

If anyone has either real-world experience with metal corrosion due to low or no calcium (as opposed to low pH) or if they are aware of scientific reasons why calcium is needed, I'd like to hear about it. Please don't take my word for it just because the science seems to indicate that it isn't a problem. I have been wrong before and will no doubt be wrong again so if real-world experience contradicts my beliefs, I certainly want to know about it. I'm just relating my understanding as it is at this time.

Thanks,
Richard

P.S. My own personal experience with metal corrosion in my own pool (we have bars in the pool just under the water line) is that the only place corrosion occurred was near where the floater with Tri-Chlor tablets had been and that I had the pool pump running 8-10 hours/day (i.e. not 24/7). I also had a thermometer corrode when I put Tri-Chlor in my skimmer. So localized low pH conditions can certainly cause corrosion. Needless to say, I don't use Tri-Chlor anymore and all of this occurred long before I got involved with this forum.