Hi all! I took my water to the pool store for testing this morning. There is TC, but no FC. I used BleachCalc and put 3.6 gallons of bleach in to raise the cl level to 18. Will this take care of the split? Or will I need more bleach to get the FC up? How do I calculate how much? I'm worried about going over 20 because I have a vinyl liner. Oh, and I've added some Lo N Slo to bring the pH down.

Here are the numbers:

In ground, vinyl 16,400 gallons
CYA 75 (this is down from over 400 in Sept!)
TC 5.5
FC 0
pH 8.1
TA 163
TH 159

Thanks so much for your advice!