I swept it all out today, backwashed the filter, added acid and two gallons of chlorine...It's looks good now but we'll see in the morning. It was hard to sweep because if I didn't do it very slowly the stuff on the bottom turned to a cloud of dust and dispersed in the water. I think part of my problem is the stuff gets stirred up in the water then settles over night so I'm not actually getting it all out of the pool when I vaccum. I have wedding cake steps and I moved those to clean under them and it was a huge cloud of brown under there.

I do not having a working pressure guage. It looks like it has water in it. How do you know if the multiport gasket is bad? I do know the little clear thing on it where you can see the color of the water when you backwash leaks really bad when I backwash. After I backwashed and rinsed I did not see any brown blowing back in from the return.