TA reduction going wrong ??

[PoolDoc]

OK, thanks.

Now, what are your current questions? I'm guessing they are:

1. How do I remove the scale?
2. Do I need to do anything else?

I'll answer those two, in any case:

1. Lowering your pH to 7.0 and keeping it there will cause your TA to drop, slowly. Low pH and low TA will maximize your chance of removing the stain / scale.
2. I would recommend testing the stain / scale to see what will remove it. You can do so by holding various chemicals against the stain / scale for a couple of minutes. I'd recommend testing in this order:

1. Vitamin C tablets
2. Dichlor or cal hypo granular chlorine.
3. Iron Out powder
4. Sodium bisulfate (pH Down aka dry acid)

You should wear plastic gloves, and put the chemicals in #2 - #4 in a old (but clean) wash rag.

[CarlD]

Let me toss in MY two cents:

As much as we love the Taylor K2006 test kit (which, using your K2005 with the K1515 is the same thing) their advice about lowering T/A is nonsense and can damage your pool. Please don't use the "Slug" method, because IF it works, it's only by accident, not because the "theory" (ie myth) behind it is any good.

As Ben pointed out, lowering your pH will lower your TA, but raising your pH after will raise TA back up again. The way around this is to lower pH as Ben said to about 7.0 and test your T/A.
If it's now good, when you want to raise pH again (after you have followed Ben's instructions for treating the stains) you'll raise it by aeration, not by adding any chemicals. That's by using a sprayer, splashing kids, pointing the return at the surface so it bubbles, etc, which will raise pH. Since your TA is now 90 you should be at a pretty good level. If it was STILL too high, you'd repeat by lowering pH to 7.0 again. So the "Slug" lowers the pH and with it the TA and whatever aeration you get raises the pH safely back up. But the "slug" is not what works--the lowering of pH does.