Ascorbic acid treatment for stains, which sequestering agent to use?

[PoolDoc]

1. Sequestering / chelating agents are marketed as if their action was complete and permanent, when in fact it's neither complete OR permanent. They TEMPORARILY solubilize metals, but once they break down, metals return to their active form and are EITHER removed from the water OR appear as new or returning stains.

2. Most methods of metal removal don't work with chelated metals; CuLater claims to do so.

3. The CuLater -- to the degree that it works, and we *think* but do not know that it does -- ONLY removes metals in the water; it has no effect on stains.

So, if you chose to pursue it, what I'm proposing is a 3-step process
1. Re-dissolve the stains -- you pretty much can't have chlorine in the pool during this period
2. Chelate them, so the metals REMAIN in the water when begin chlorinating again, and don't re-stain the pool. (Temporary state)
3. REMOVE them with CuLator, or another method

None of what you need to do is difficult, but it is picky: you have to do the right thing in the right order, to make it work. I anticipate that you'll need to spend about $150 + a K-2006 (if you don't have one), from start to finish. If you want to go ahead, I'll 'whip' up a recipe and give you an order list.

You asked, above:

Is there a preferred type/brand? If not, can I ask my local pool supply store to provide 'sequestration agent' and be confident he/she will sell me the correct chemical?

Your question pretty much nails the problem we've had here: you can NOT trust the pool store to give you the right chemical. Not only do they not know (usually) what the right chemical is, the chemical companies generally make it difficult to find out exactly what's in "Metal Free" or "Metal Magic" or whatever. We've run into one case this year, with Natural Chemistry's "Metal Free", in which they have COMPLETELY changed ingredients. Same container; same basic instructions; same sales claims --- completely different ingredients, neither of which -- by the way -- are very desirable ones!

To do this correctly, you need to use the right chemicals at each step -- the brand doesn't matter, but the chemicals do. We haven't been able to do what I'm proposing, because we haven't been able to make sure people got EXACTLY the right things. Now that Amazon is selling a wide range of pool supplies, I can give you a link to THIS, and THIS and THIS, allowing me to create a fairly exact recipe. The head chemist at Kem-Tek not only knows of PoolForum, but likes it and is willing to tell me EXACTLY what's in his blends, so I can know how to use them.

So, I'm ready to go . . . if you are! I really, really would like it, if you could take pictures as you went through this. In one sense, this is an experiment. I know that it will 'work', but not how well. My guess is, you'll be able to remove most, but not 100% of the stains.

If you are willing to pursue this, I also want to get Chem_Geek (who knows more pool chemistry, analytically, than I do, or for that matter, than anyone else in the world -- literally!) and Marie (who has helped many people here with stains) to sit in on this thread. You'll be the first case of a new, precise, stain removal process!