Quote Originally Posted by Cookieman View Post
When she heard calcium was only 90, she said Jack's products need calcium levels of 200-400 to work best as it gives it something for the metal to bind to. First I had heard of that. She believed that is why even double dosing did not sequester all the metal. . . . . Will calcium addition affect PH?
Last first: adding calcium (chloride) will not affect the pH much, if at all.

Regarding the "calcium giving the metal something to bind to" . . . She may be referring to something real, but not as stated. Calcium is ALSO a metal, and you can't bind iron to another metal in pool water. That is, you're not going to form something like ferric calcium.

BUT, I know from my own experience that having calcium carbonate -- marble dust, plaster dust, or cal hypo residue -- DOES collect metal out of the water. Essentially, you end up staining the dust, instead of the pool.

The whole "HEDP needs calcium" to work doesn't make sense to me, and it doesn't really fit with the old Monsanto Dequest manuals I have, but then I don't understand chelation chemistry at any fundamental level. So, again, it's possible she's referring to something real, but with a slightly bogus explanation


Quote Originally Posted by mbar View Post
One thing I noticed is when the pool gets milky white after the ascorbic acid treatment the stains don't tend to come back. I think it is when the calcium binds with the HEDP and then it turns the pool milky.
That's interesting, Marie, but I have no idea why that would be happening. I'm going to ask Chem_Geek to read through your's and Cookieman's posts and this thread, and see if he has any possible analytical explanation of what might be going on. It's a whole lot easier to make good recommendations, when you understand what's happening. . . and why!