Very Cloudy/Foaming issues

[CarlD]

By "High alkalinity" do you mean high Total Alkalinity or an elevated pH lever? "High alkalinity" shouldn't be the source of your problems in either case. And, if it's Total Alkalinity, just adding Muriatic Acid isn't going to fix it.

I'm thinking there's nothing wrong with your filter, but that you've been advised (and sold) to throw in so much junk that clearing it all out is going to take some time.

BD, WM: what do you think of this recommendation?

1) Give us a full set of test numbers: FC, CC or TC, pH, CH, T/A and CYA.
2) Backwash. Then add just enough DE (about 1/4 to 1/3) cup through your skimmer to raise your PSI 1lb.
3) adjust pH and FC levels to recommended shock level for your CYA level (http://pool9.net/cl-cya/)
4 Buy a package of "Skimmer Socks" (or similar skimmer liners under another brand name). They are cheap. Put one in your skimmer.
5) Run your pump 24/7. If it's a two speed, run it on High. Let this run for a day or two.
6) See if the pressure on the pump went up, and if the skimmer sock is full. If so, backwash and add more DE and wash out the skimmer sock and replace.
7) Keep pH between 7.2 and 7.8, and keep FC at shock level.
8) Let us know what happens and we can recommend the next step/steps.