We typically find that pool store testing is not usually too reliable. It is much better to test the water yourself. But, most kits cannot measure chlorine levels past 5ppm. I'm assuming your kit uses an OTO chlorine test. Does the sample turn yellow to show the chlorine level? It is so much better to use a kit that is not limited to that 5ppm upper limit. That is why we like the Taylor K2006 or 2006C (better buy). It can measure chlorine readings WAY higher than 5pm. When you have algae, you have to shock to higher chlorine levels in order to kill the algae and you need to have some reliable way to test those higher chlorine levels. Thus the reason why we think it is important to have the K2006 kit. You won't be able to find it locally but you can get it through this link:> http://pool9.net/tk/

I'm inclined to think that your pH is 7.6 since both pool stores got the same reading. Your test kit will give falsely high pH readings when the chlorine is over 5ppm. If your chlorine is over 5ppm, (or over 10ppm with a Taylor kit), you can dilute the sample by mixing equal parts of pool water and distilled water and then running the pH test with that mixture.

Needed shock levels are based on your CYA level. You got a reading of 60 and then one of 99 so who knows what your level actually is. Again, another reason to have a good kit.

For now, I'm going to advise that you shock up to about 15ppm. Using 12.5% liquid chlorine (sodium hypochlorite) is fine although sometimes it may not really be the percentage that the label says. But, at any rate, assuming that it is 12.5%, each, in a 26K gallon pool, each quart will add about 1ppm of chlorine.

Please order a K2006 kit. Also, verify for me that your chlorine test is an OTO kit (turns yellow) and then I can advise you further.

Hope this helps.

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