The pump is a brand new (less than a week old) Pentair Dynamo 3/4hp two speed pump. I added the DE while the pump was on the high speed setting, and left the pump on high for the 12 hours or so following the introduction of the DE. Even after the pump was set to low, there still remained a lot of particulate matter that could be seen in the pool light.

During the daytime, the pool water does look crystal clear. The only time I can see any particles in the water is when it flows past the light at night.

The filter is a new (installed in early June) Hayward 220T with new filter sand.

I had just backwashed prior to introducing the DE to the filter. The normal pump pressure is 9.5 psi on the high setting.