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

[PoolDoc]

OK. Here's the process:

1. Lower the pH to 7.0 using muriatic acid.
2. Clean your filter. Leave cartridge OUT of filter; leave pump on 24/7!
3. Test the chlorine; add sodium thiosulfate to remove it => approximately 2 tablespoons per ppm of chlorine.
4. Add polyquat, 1 hour after adding the thiosulfate
5. Add 1# ascorbic acid.
6. Check pH; add acid as needed to maintain pH at 7.0 or a little below.
7. Brush stained areas every 4 - 8 hours.
8. OPTIONAL: After 24 hours, if stains are not completely removed, put 1/2 of ascorbic acid in a freezer bag, fill it with enough water to make a slurry, and enter the pool with googles and the bag. Continue with 2nd 1/2# if needed.
9. OPTIONAL: Holding the bag underwater, 'drizzle' the slurry onto resistant stain areas.
10. OPTIONAL: Wait 24 hours more (continue to keep pH down). If stains remain, make an similar slurry with Iron Out, and try again.
11. Add HEDP dose; wait 4 hours
12. Replace cartridge in filter; continue to keep pH low.
13. Begin adding plain 6% household bleach, 1/2 gallon every 2-4 hours, till you have a measurable chlorine level. Try not to exceed 5 ppm.
14. Place CuLator baggie in skimmer.

Notes:

• With your alkalinity as high as it is, your pool's pH is likely to want to rise. Be diligent about keeping the pH below 7.2.
• Once you begin this process, leave your pump on 24/7 for the next month.
• Adjust your pool return eyeballs so the return stream(s) is/are NOT directed against any pool surface.
• Once you have the CuLator in the basket, you can gradually begin bringing the FC level up to what it should be -- 5 - 10 ppm, given your CYA level.
• Once you have a FC level of 2 ppm or higher, you can resume swimming.
• Once the chlorine level is normal, use borax, 1/2 box at a time, to raise your pH to 7.6 - 7.8.
• Once your pH reaches that level, switch from bleach to the cal hypo. (instructions below)
• Watch your filter pressure: once you switch to cal hypo, you may find that your pressure builds up quickly. This is GOOD -- but you'll need to clean the filter every time the pressure goes up by 7 - 10 pounds.
• You can dose your pool to 10 ppm FC, and let it drift down to 5 ppm before adding more.
• Using the CuLator *and* cal hypo added in the manner described is sort of a 'belt & suspenders' approach. Hopefully, the CuLator will work as well as advertised. But if not, the cal hypo slurry on your filter will ALSO tend to trap any metals in the water, and when you clean your filter, these metals will be removed from the pool.

To add the cal hypo:

• Remove the CuLator baggie from the skimmer.
• Make SURE there are no other chemicals in the skimmer.
• With the pump running, add the cal hypo (1/2lb per dose) directly to the skimmer, with the pump running.
• A single 1/2 lb dose should add about 5 ppm FC.
• After all the cal hypo is gone from the skimmer, replace the CuLator baggie