I did backwash the filter. Extensively. I backwashed for several minutes and caught samples several times. It did take a long time for the water to clear. Then I rinsed and repeat, 2-3 times. I tried to see if any sand was coming through the backwash but I never detected much, but it was hard to disceren from all the "junk" coming out either.

When I backwash my start-up pressure is normally 17-20 psi. I added about 3/4 of a 'cup' of DE to the skimmers until the pressure reached ~1-2 psi above clean pressure. Funny thing was that I came back about 15-20 minutes later and the pressure was running ~25 psi. I then shut the filter off for a few minutes and re-started, and , voila, the pressure was back about ~21-22 psi.

What bothers me is that the filter pressure will rise, over time, running normally. I now have the pump running on low speed 24/7 hoping that under low speed the sand filter can catch the stuff that normally gets through. I have the DE in the filter, but the water is still cloudy.

I need to pull the top off next and add some sand. I'm gonna put unions in on every connection. I'm gonna start with 2 bags, unless the visible level looks low enough. Then I'm gonna put a throttle valve on the BW line and pinch it down. I checked out what the flow under low speed looks like during BW and it still does about 20-30 GPM so I could just try that too.

I will try the other DE test also but I have never seen the DE blow back into the pool but I will give it a look again.