I would do a deep clean of your sand filter. Here is a link:Deep Cleaning a Sand Filter I am not seeing any unions so you will need to get some and plan on installing them for now and the future. I would go ahead and add them to your pump as well. That means you need a total of 5. Here is what they might look like:pvc unions - Google Search The DE pushing your pressure up shows that it is helping. I would keep doing it as often as you can. We will have to think about how to keep your from having to do this every year. Once we get it clear maybe we can go over your closing process. Kim

I agree with Kim. A good deep cleaning might serve you well. Sand should last as long as the filter itself unless someone added chemicals that would have altered the sands composition. Your plumbing looks fairly straight-forward. Most common sized PVC is probably 2 - 2.5 inches in size, but that shouldn't effect too much if all you have to pump to are the return jets. You have a good 2 speed/1.5 HP pump. So I think you're on-track with a SLAM. But keep in mind with a CYA of 30, the SLAM level is an FC of 12. Slightly over is okay, but too far over only wastes bleach. Once your CC stay below .5, and the water is clear, then it may be time to try an OCLT. Until then, patience is the best medicine .... along with Maintaining the FC.