Two thoughts: You need to test more properly for FC and CC levels, and for metal content in your water.

1) Have you shocked your pool up to 15ppm? TC can be misleading because TC=FC + CC. If you have a substantial CC reading then you need to raise your FC level to 15, not your TC. You should get an FAS-DPD chlorine test kit to measure that. If you click on my sig, you can get a link to the Taylor K-2006 or K-2006C kits, the ones we recommend. I don't get anything for it but a small amount goes to Ben to help maintain the PoolForum site. Normally, 3 1/3 gallons of 6% bleach will add 15ppm of FC to 15,000 gallons, but that much might bleach your liner.

2) My other thought is that you have a metals problem and should check for copper and iron content. If you do, then adding more chlorine will make the green worse, but the pool will be safe to use. Still, you'll have to go through metal-sequestering procedures using HEDP, but I'm not the metals person.

Carl

PS: I see that I don't have the sig link right now. Check with PoolDoc's and Watermom's posts and you should find it there. C