Are you diluting your water sample before running the pH test? With the K2006 kit, if your chlorine level is higher than 10ppm, your pH test will be inaccurate. (With other kits besides the Taylors, the pH test is inaccurate when chlorine levels are higher than 5ppm.) If you haven't been, do so by mixing a 1/4 cup pool water with 1/4 cup distilled water. Then, use that to run the pH test but you don't have to multiply the results by anything. Just read it.

Let's do a test on your filter to make sure that it is working properly. Get a small bag of DE. Add a small amount to the skimmer and watch the return jet to see if any white powder is shooting back out. Report back with your result. If you see it coming out of the jet, then your filter needs work. If not, the DE may actually help you sand filter catch some of the stuff better. More about it here:> http://pool9.net/de-test/