I added DE to my sand filter today to aid in filtration. I had a reading of 13.5 psi on the pump and added about 4 cups of DE to the skimmer. The gauge went to 15 psi and I stopped adding DE. I then got in the pool and started to vacuum. I use goggles and a snorkel and get under the water when I vacuum. To my surprise I saw the DE in the water. After a few minutes I went and looked at the pump and it was back to 13.5 psi. What's up? My sand filter has been working great. All I've had is a small amount of fine brown dirt type substance settling in the low spots of the liner. That's what I was hoping to catch with the DE. But, now the DE is in the pool. Again, What's up?