I opened the cover 3 days ago. Pool was black. Tested the water 0 Cl pH 7.5, CYA 0. Added dichlor 78% to raise Cl to 13. After the first hour dropped down to 0 again. Bumped it back up and now it is 18 and holding with a 2.5 CC level. The water is still really brown. I have vacumed to waste twice; brushed the sides religiously and still have the high Cl reading. The high Cl reading has me bugged. I can't figure that out. Have I not hit the threshold for the algae? Here are my most current readings: Cl 18, CC 2.5, pH 7.5, TA 80, CYA 0; CH 500. I know I need to replace 50% of the water to lower CH. My question is should I go ahead and replace water or bump up the Cl level to the breakpoint first?