1. Drain any water you've added.
2. Get some polyquat, muriatic acid, borax, and chlorine tabs (99% trichlor!)
3. Check your filter and make sure it's FULL of sand.
4. Refill, and add a full 'algae' dose of polyquat as soon as you start filling.
5. Test the pH and add acid as needed to keep the pH below 7.2.
6. If you overshoot, use borax to keep the pH above 6.8.
7. Start running the pump ASAP, run it 24/7
8. Continue dosing with polyquat -- maintenance dose -- every 2 days.
9. Do NOT begin swimming (or aerating) for 3 days after the pool is full.
10. Do NOT backwash more than you have to do.
11. After 24 hours of continuously filtering a full pool, add 1 chlorine tab to the skimmer.
12. Add 1 more tab every 24 hours, till your chlorine level is above 2.0
13. Begin adding borax every 12 hours to raise your pH above 7.6. Do not raise it more than 0.2 points per dose.
14. Do NOT begin swimming till the pH is >7.6 and the chlorine is > 1.5 ppm
15. When you need to add more water, do so sl-o-ow-ly, via the skimmer, with the pump running 24/7 and with at least 1 full tab in the skimmer.
The process above will tend to result in the iron coming out on the filter, rather than in the pool. You MUST make changes gradually, so the filter can stay ahead of the water. If you make sudden changes to the pH or chlorine levels, you'll tend to repeat the iron mess you have above.
Links:
polyquat => Kem-Tek 311-6 Pool and Spa 60-Percent Concentrated Algaecide, 1 Quart
borax => 20 Mule Team Borax from Walmart or elsewhere
muriatic acid info => PoolForum Guide to Using Muriatic
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