The case of the somewhat old"ish" filter and the cloudy pool

Opened the pool quite late this year because the weather just couldn't decide what it wanted to do. Put brand new pool filter sand (yes it was the correct type of filter sand purchased at the pool store) into the filter. I followed the directions explicitly! I added my usual opening chemicals (I use Baquacil) and we continued on our way. The pool kept getting cloudier and cloudier. First I tried some flocculant that I had from last year just in the skimmer. No change. Tried reading up on it, decided my calcium must be too high so I took a sample in and found that my water look pretty good. If anything the calcium was a little low. PH was a little high, but only a little. They suggested using the whole pool flocculant method. We did that which allowed us to see the nice white coated bottom, which we tried to vacuum but didn't seem to do anything but stir it up. Then noticed that when trying to backwash there was little water coming out, unlike years past. We took the filter apart last night and felt around in the sand and my husband felt sure that the sand had clogged up. It's brand new sand! Anyway, I called pool store today and they said it's unlikely that it's the sand that is clogged. I did see cloudy water poofs going into the pool when the filter was on backwash so that would mean the spider gasket was bad. I purchased what we thought was the correct one this afternoon. My filter is a Hayward S190TSCH, that is what the filter itself says. Apparently it's so old the internet doesn't recognize it. How do I figure out what size the spider gasket is supposed to be? The one that was in it was yellow and had prongs sticking through the underside. Sorry for the long story, but thanks for the assist!