I'll start by saying I have very little idea of what I'm doing, so it's entirely possible this problem is of my own making. In the interest illustrating my potential stupidity in order to fix the problem, this may be long.
I have an inground pool with a Purex Triton FNS Plus 48 DE filter. (We just bought this property a few months ago and the pool has not been open in 4 years.) I started opening the pool a few weeks ago. The pool was more like a pond, so I went with maintaining a high shock level of chlorine, scrubbing the walls and bottom, and vacuuming the pool to the try and clear it up. It cleared to a cloudy slightly green color and wouldn't go any further and it was around this point that I realized the DE I put in after backwashing was blowing back into the pool in great plumes. I took the filter apart and found a couple of the grids had small holes and the top manifold was cracked. Rather than mess with trying to replace the individual grids and the manifold, I ordered a whole new grid assembly.
Got the grid assembly, installed it, and put in the what I thought was the recommended amount of DE. The pool place told me to use a coffee can. My filter should have about 4.8 pounds of DE and I was told to use "about 10" scoops from the can, and that's what I did. The psi after coating was at 18. The next morning, I saw an improvement in the pool water. The day after that, I saw an even greater improvement. The water was still cloudy, but I could see the bottom clearly enough to know the vinyl liner has a pattern on the bottom. (And that I did a horrible job vacuuming when I couldn't see...)
So, I vacuumed again. Whenever the psi got above 30, I backwashed and after each time I backwashed, I added about 2 pounds of DE (as recommended by the pool place). In that first vacuum session when I could see the bottom, I backwashed about 6 times. The next day (which brings me to yesterday), I noticed the water was clouding up again, but I thought it was because I put the Tiger Shark robo vac in the pool that morning. I took it out and put it away. The pressure wasn't high on the filter, so I decided to vacuum manually until it was high and then backwash. As I was vacuuming, I noticed the water from the jets was blowing in the same color as the dirt on the bottom and that the pool was getting worse. I stopped vacuuming, backwashed the filter, added another 2 pounds of DE, and called it a day. Before going to bed last night, I checked the filter, found the pressure was up, so I backwashed and added another 2 pounds of DE. I checked the jet and found a huge plume of the clean DE blowing into the pool. This morning, the water is right back to the cloudiness it was before I installed the new filter grid.
What have I done wrong and how can I fix it?