Although I have not previously posted, I wanted to thank all the great people on these Boards.

Here is the situation: I incurred my first green algae problem on 7/4 and "accidentally" dumped too much chlorine and shock into the pool (only 18' above ground round). When the water finally cleared, I tested the water and discovered excessive pH (8.4) and, of course, Cl. I used a dilution method with OTO and estimated a level of 50+ ppm. I adjusted the pH with muriatic acid. The rest of the numbers appear ok according to the test strips (could not find a "real" kit anywhere). The only problem was the excessive chlorine. However, the weather indicated that it was going to be over 90 degrees in 2 days, so I investigated a chlorine neutralizer. A local pool company sold a 10 pound jug to me, but I don't know what the exact chemical is. My best guess is sodium sulfate since the label indicated that 3 oz would reduce 10,000 gallons by 1 ppm. Since I needed to lower an estimated 40 ppm, I played it conservative and used about 3.3 pounds (I calculated 5.75 or so).

Here's the problem. The test strips (HTH 6-way) show 2 ppm. A diluted OTO 3/1 = 16+ ppm and a diluted OTO 5/1 = 12 or so.

I have no idea what the actual chlorine level is.

So, Chem_Geek or anyone else:

1. Now that my water is full of sulfates, which one of the test methods is giving an accurate measurement?

2. Also, assuming I used sodium sulfate, I was wondering what the chemical reaction was. (I thought I smelled something, sulfur dioxide?)

Thanks to all for the great info, I keep a cheat sheet on how to deal with all the water problems.